From c76b0066fb2ae01a28630662cb04a043cc5841cb Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Mon, 28 Nov 2016 01:13:59 -0800
Subject: 3700

Reorder products of some functions in the edit/ and sandbox/ apps. My
recent realization: always return 'real' products before ones that just
indicate an ingredient is mutable.
---
 edit/002-typing.mu                            |  48 ++++------
 edit/003-shortcuts.mu                         | 128 ++++++++++----------------
 edit/004-programming-environment.mu           |   4 +-
 edit/012-editor-undo.mu                       |   4 +-
 html/edit/002-typing.mu.html                  |  48 ++++------
 html/edit/003-shortcuts.mu.html               | 128 ++++++++++----------------
 html/edit/004-programming-environment.mu.html |   4 +-
 html/edit/012-editor-undo.mu.html             |   4 +-
 sandbox/002-typing.mu                         |  48 ++++------
 sandbox/003-shortcuts.mu                      |  86 ++++++-----------
 sandbox/004-programming-environment.mu        |   2 +-
 sandbox/012-editor-undo.mu                    |   4 +-
 12 files changed, 193 insertions(+), 315 deletions(-)

diff --git a/edit/002-typing.mu b/edit/002-typing.mu
index a584e6a3..4f704f0d 100644
--- a/edit/002-typing.mu
+++ b/edit/002-typing.mu
@@ -34,7 +34,7 @@ def editor-event-loop screen:&:screen, console:&:console, editor:&:editor -> scr
     # keyboard events
     {
       break-if is-touch?
-      screen, editor, go-render?:bool <- handle-keyboard-event screen, editor, e
+      go-render?:bool <- handle-keyboard-event screen, editor, e
       {
         break-unless go-render?
         screen <- editor-render screen, editor
@@ -161,11 +161,10 @@ def snap-cursor screen:&:screen, editor:&:editor, target-row:num, target-column:
 
 # Process an event 'e' and try to minimally update the screen.
 # Set 'go-render?' to true to indicate the caller must perform a non-minimal update.
-def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> screen:&:screen, editor:&:editor, go-render?:bool [
+def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> go-render?:bool, screen:&:screen, editor:&:editor [
   local-scope
   load-ingredients
-  go-render? <- copy 0/false
-  return-unless editor
+  return-unless editor, 0/don't-render
   screen-width:num <- screen-width screen
   screen-height:num <- screen-height screen
   left:num <- get *editor, left:offset
@@ -184,11 +183,10 @@ def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> screen:&:
     <handle-special-character>
     # ignore any other special characters
     regular-character?:bool <- greater-or-equal c, 32/space
-    go-render? <- copy 0/false
-    return-unless regular-character?
+    return-unless regular-character?, 0/don't-render
     # otherwise type it in
     <insert-character-begin>
-    editor, screen, go-render?:bool <- insert-at-cursor editor, c, screen
+    go-render? <- insert-at-cursor editor, c, screen
     <insert-character-end>
     return
   }
@@ -197,11 +195,10 @@ def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> screen:&:
   assert is-keycode?, [event was of unknown type; neither keyboard nor mouse]
   # handlers for each special key will go here
   <handle-special-key>
-  go-render? <- copy 1/true
-  return
+  return 1/go-render
 ]
 
-def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool [
+def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> go-render?:bool, editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
@@ -233,8 +230,7 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor
     break-if overflow?
     move-cursor screen, save-row, save-column
     print screen, c
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
   {
     # not at right margin? print the character and rest of line
@@ -246,9 +242,8 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor
     curr-column:num <- copy save-column
     {
       # hit right margin? give up and let caller render
-      go-render? <- copy 1/true
       at-right?:bool <- greater-than curr-column, right
-      return-if at-right?
+      return-if at-right?, 1/go-render
       break-unless curr
       # newline? done.
       currc:char <- get *curr, value:offset
@@ -259,11 +254,9 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor
       curr <- next curr
       loop
     }
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
-  go-render? <- copy 1/true
-  return
+  return 1/go-render
 ]
 
 # helper for tests
@@ -740,8 +733,7 @@ after <insert-character-special-case> [
       break-unless below-screen?
       <scroll-down>
     }
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -863,14 +855,13 @@ after <handle-special-character> [
     newline?:bool <- equal c, 10/newline
     break-unless newline?
     <insert-enter-begin>
-    editor <- insert-new-line-and-indent editor, screen
+    insert-new-line-and-indent editor, screen
     <insert-enter-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
-def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool [
+def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   cursor-row:num <- get *editor, cursor-row:offset
@@ -892,7 +883,6 @@ def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:edit
     below-screen?:bool <- greater-or-equal cursor-row, screen-height  # must be equal, never greater
     break-unless below-screen?
     <scroll-down>
-    go-render? <- copy 1/true
     cursor-row <- subtract cursor-row, 1  # bring back into screen range
     *editor <- put *editor, cursor-row:offset, cursor-row
   }
@@ -906,7 +896,7 @@ def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:edit
   {
     indent-done?:bool <- greater-or-equal i, indent
     break-if indent-done?
-    editor, screen, go-render?:bool <- insert-at-cursor editor, 32/space, screen
+    insert-at-cursor editor, 32/space, screen
     i <- add i, 1
     loop
   }
@@ -1048,8 +1038,7 @@ after <handle-special-key> [
     paste-start?:bool <- equal k, 65507/paste-start
     break-unless paste-start?
     *editor <- put *editor, indent?:offset, 0/false
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -1058,8 +1047,7 @@ after <handle-special-key> [
     paste-end?:bool <- equal k, 65506/paste-end
     break-unless paste-end?
     *editor <- put *editor, indent?:offset, 1/true
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
diff --git a/edit/003-shortcuts.mu b/edit/003-shortcuts.mu
index b747a869..1b352fdd 100644
--- a/edit/003-shortcuts.mu
+++ b/edit/003-shortcuts.mu
@@ -29,11 +29,10 @@ after <handle-special-character> [
     tab?:bool <- equal c, 9/tab
     break-unless tab?
     <insert-character-begin>
-    editor, screen, go-render?:bool <- insert-at-cursor editor, 32/space, screen
-    editor, screen, go-render?:bool <- insert-at-cursor editor, 32/space, screen
+    insert-at-cursor editor, 32/space, screen
+    insert-at-cursor editor, 32/space, screen
     <insert-character-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -72,7 +71,7 @@ after <handle-special-character> [
     delete-previous-character?:bool <- equal c, 8/backspace
     break-unless delete-previous-character?
     <backspace-character-begin>
-    editor, screen, go-render?:bool, backspaced-cell:&:duplex-list:char <- delete-before-cursor editor, screen
+    go-render?:bool, backspaced-cell:&:duplex-list:char <- delete-before-cursor editor, screen
     <backspace-character-end>
     return
   }
@@ -81,31 +80,28 @@ after <handle-special-character> [
 # return values:
 #   go-render? - whether caller needs to update the screen
 #   backspaced-cell - value deleted (or 0 if nothing was deleted) so we can save it for undo, etc.
-def delete-before-cursor editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool, backspaced-cell:&:duplex-list:char [
+def delete-before-cursor editor:&:editor, screen:&:screen -> go-render?:bool, backspaced-cell:&:duplex-list:char, editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
   data:&:duplex-list:char <- get *editor, data:offset
   # if at start of text (before-cursor at § sentinel), return
   prev:&:duplex-list:char <- prev before-cursor
-  go-render?, backspaced-cell <- copy 0/no-more-render, 0/nothing-deleted
-  return-unless prev
+  return-unless prev, 0/no-more-render, 0/nothing-deleted
   trace 10, [app], [delete-before-cursor]
   original-row:num <- get *editor, cursor-row:offset
-  editor, scroll?:bool <- move-cursor-coordinates-left editor
+  scroll?:bool <- move-cursor-coordinates-left editor
   backspaced-cell:&:duplex-list:char <- copy before-cursor
   data <- remove before-cursor, data  # will also neatly trim next/prev pointers in backspaced-cell/before-cursor
   before-cursor <- copy prev
   *editor <- put *editor, before-cursor:offset, before-cursor
-  go-render? <- copy 1/true
-  return-if scroll?
+  return-if scroll?, 1/go-render
   screen-width:num <- screen-width screen
   cursor-row:num <- get *editor, cursor-row:offset
   cursor-column:num <- get *editor, cursor-column:offset
   # did we just backspace over a newline?
   same-row?:bool <- equal cursor-row, original-row
-  go-render? <- copy 1/true
-  return-unless same-row?
+  return-unless same-row?, 1/go-render
   left:num <- get *editor, left:offset
   right:num <- get *editor, right:offset
   curr:&:duplex-list:char <- next before-cursor
@@ -114,8 +110,7 @@ def delete-before-cursor editor:&:editor, screen:&:screen -> editor:&:editor, sc
   {
     # hit right margin? give up and let caller render
     at-right?:bool <- greater-or-equal curr-column, right
-    go-render? <- copy 1/true
-    return-if at-right?
+    return-if at-right?, 1/go-render
     break-unless curr
     # newline? done.
     currc:char <- get *curr, value:offset
@@ -132,9 +127,10 @@ def delete-before-cursor editor:&:editor, screen:&:screen -> editor:&:editor, sc
   go-render? <- copy 0/false
 ]
 
-def move-cursor-coordinates-left editor:&:editor -> editor:&:editor, go-render?:bool [
+def move-cursor-coordinates-left editor:&:editor -> go-render?:bool, editor:&:editor [
   local-scope
   load-ingredients
+  go-render?:bool <- copy 0/false
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
   cursor-row:num <- get *editor, cursor-row:offset
   cursor-column:num <- get *editor, cursor-column:offset
@@ -146,12 +142,10 @@ def move-cursor-coordinates-left editor:&:editor -> editor:&:editor, go-render?:
     trace 10, [app], [decrementing cursor column]
     cursor-column <- subtract cursor-column, 1
     *editor <- put *editor, cursor-column:offset, cursor-column
-    go-render? <- copy 0/false
     return
   }
   # if at left margin, we must move to previous row:
   top-of-screen?:bool <- equal cursor-row, 1  # exclude menu bar
-  go-render?:bool <- copy 0/false
   {
     break-if top-of-screen?
     cursor-row <- subtract cursor-row, 1
@@ -345,25 +339,23 @@ after <handle-special-key> [
     delete-next-character?:bool <- equal k, 65522/delete
     break-unless delete-next-character?
     <delete-character-begin>
-    editor, screen, go-render?:bool, deleted-cell:&:duplex-list:char <- delete-at-cursor editor, screen
+    go-render?:bool, deleted-cell:&:duplex-list:char <- delete-at-cursor editor, screen
     <delete-character-end>
     return
   }
 ]
 
-def delete-at-cursor editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool, deleted-cell:&:duplex-list:char [
+def delete-at-cursor editor:&:editor, screen:&:screen -> go-render?:bool, deleted-cell:&:duplex-list:char, editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
   data:&:duplex-list:char <- get *editor, data:offset
   deleted-cell:&:duplex-list:char <- next before-cursor
-  go-render? <- copy 0/false
-  return-unless deleted-cell
+  return-unless deleted-cell, 0/don't-render
   currc:char <- get *deleted-cell, value:offset
   data <- remove deleted-cell, data
   deleted-newline?:bool <- equal currc, 10/newline
-  go-render? <- copy 1/true
-  return-if deleted-newline?
+  return-if deleted-newline?, 1/go-render
   # wasn't a newline? render rest of line
   curr:&:duplex-list:char <- next before-cursor  # refresh after remove above
   cursor-row:num <- get *editor, cursor-row:offset
@@ -374,8 +366,7 @@ def delete-at-cursor editor:&:editor, screen:&:screen -> editor:&:editor, screen
   {
     # hit right margin? give up and let caller render
     at-right?:bool <- greater-or-equal curr-column, screen-width
-    go-render? <- copy 1/true
-    return-if at-right?
+    return-if at-right?, 1/go-render
     break-unless curr
     # newline? done.
     currc:char <- get *curr, value:offset
@@ -427,7 +418,7 @@ after <handle-special-key> [
     <move-cursor-begin>
     before-cursor <- copy next-cursor
     *editor <- put *editor, before-cursor:offset, before-cursor
-    editor, go-render?:bool <- move-cursor-coordinates-right editor, screen-height
+    go-render?:bool <- move-cursor-coordinates-right editor, screen-height
     screen <- move-cursor screen, cursor-row, cursor-column
     undo-coalesce-tag:num <- copy 2/right-arrow
     <move-cursor-end>
@@ -435,7 +426,7 @@ after <handle-special-key> [
   }
 ]
 
-def move-cursor-coordinates-right editor:&:editor, screen-height:num -> editor:&:editor, go-render?:bool [
+def move-cursor-coordinates-right editor:&:editor, screen-height:num -> go-render?:bool, editor:&:editor [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor before-cursor:offset
@@ -453,13 +444,11 @@ def move-cursor-coordinates-right editor:&:editor, screen-height:num -> editor:&
     cursor-column <- copy left
     *editor <- put *editor, cursor-column:offset, cursor-column
     below-screen?:bool <- greater-or-equal cursor-row, screen-height  # must be equal
-    go-render? <- copy 0/false
-    return-unless below-screen?
+    return-unless below-screen?, 0/don't-render
     <scroll-down>
     cursor-row <- subtract cursor-row, 1  # bring back into screen range
     *editor <- put *editor, cursor-row:offset, cursor-row
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
   # if the line wraps, move cursor to start of next row
   {
@@ -478,12 +467,11 @@ def move-cursor-coordinates-right editor:&:editor, screen-height:num -> editor:&
     cursor-column <- copy left
     *editor <- put *editor, cursor-column:offset, cursor-column
     below-screen?:bool <- greater-or-equal cursor-row, screen-height  # must be equal
-    return-unless below-screen?, editor, 0/no-more-render
+    return-unless below-screen?, 0/no-more-render
     <scroll-down>
     cursor-row <- subtract cursor-row, 1  # bring back into screen range
     *editor <- put *editor, cursor-row:offset, cursor-row
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
   # otherwise move cursor one character right
   cursor-column <- add cursor-column, 1
@@ -710,10 +698,9 @@ after <handle-special-key> [
     trace 10, [app], [left arrow]
     # if not at start of text (before-cursor at § sentinel)
     prev:&:duplex-list:char <- prev before-cursor
-    go-render? <- copy 0/false
-    return-unless prev
+    return-unless prev, 0/don't-render
     <move-cursor-begin>
-    editor, go-render? <- move-cursor-coordinates-left editor
+    go-render? <- move-cursor-coordinates-left editor
     before-cursor <- copy prev
     *editor <- put *editor, before-cursor:offset, before-cursor
     undo-coalesce-tag:num <- copy 1/left-arrow
@@ -979,16 +966,17 @@ after <handle-special-key> [
     move-to-previous-line?:bool <- equal k, 65517/up-arrow
     break-unless move-to-previous-line?
     <move-cursor-begin>
-    editor, go-render? <- move-to-previous-line editor
+    go-render? <- move-to-previous-line editor
     undo-coalesce-tag:num <- copy 3/up-arrow
     <move-cursor-end>
     return
   }
 ]
 
-def move-to-previous-line editor:&:editor -> editor:&:editor, go-render?:bool [
+def move-to-previous-line editor:&:editor -> go-render?:bool, editor:&:editor [
   local-scope
   load-ingredients
+  go-render?:bool <- copy 0/false
   cursor-row:num <- get *editor, cursor-row:offset
   cursor-column:num <- get *editor, cursor-column:offset
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
@@ -1009,14 +997,12 @@ def move-to-previous-line editor:&:editor -> editor:&:editor, go-render?:bool [
       break-if at-newline?
       curr:&:duplex-list:char <- before-previous-line curr, editor
       no-motion?:bool <- equal curr, old
-      go-render? <- copy 0/false
       return-if no-motion?
     }
     {
       old <- copy curr
       curr <- before-previous-line curr, editor
       no-motion?:bool <- equal curr, old
-      go-render? <- copy 0/false
       return-if no-motion?
     }
     before-cursor <- copy curr
@@ -1042,15 +1028,13 @@ def move-to-previous-line editor:&:editor -> editor:&:editor, go-render?:bool [
       *editor <- put *editor, cursor-column:offset, cursor-column
       loop
     }
-    go-render? <- copy 0/false
     return
   }
   {
     # if cursor already at top, scroll up
     break-unless already-at-top?
     <scroll-up>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -1213,14 +1197,14 @@ after <handle-special-key> [
     move-to-next-line?:bool <- equal k, 65516/down-arrow
     break-unless move-to-next-line?
     <move-cursor-begin>
-    editor, go-render? <- move-to-next-line editor, screen-height
+    go-render? <- move-to-next-line editor, screen-height
     undo-coalesce-tag:num <- copy 4/down-arrow
     <move-cursor-end>
     return
   }
 ]
 
-def move-to-next-line editor:&:editor, screen-height:num -> editor:&:editor, go-render?:bool [
+def move-to-next-line editor:&:editor, screen-height:num -> go-render?:bool, editor:&:editor [
   local-scope
   load-ingredients
   cursor-row:num <- get *editor, cursor-row:offset
@@ -1243,8 +1227,7 @@ def move-to-next-line editor:&:editor, screen-height:num -> editor:&:editor, go-
       break-unless no-motion?
       scroll?:bool <- greater-than cursor-row, 1
       break-if scroll?, +try-to-scroll
-      go-render? <- copy 0/false
-      return
+      return 0/don't-render
     }
     cursor-row <- add cursor-row, 1
     *editor <- put *editor, cursor-row:offset, cursor-row
@@ -1268,8 +1251,7 @@ def move-to-next-line editor:&:editor, screen-height:num -> editor:&:editor, go-
       *editor <- put *editor, cursor-column:offset, cursor-column
       loop
     }
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
   +try-to-scroll
   <scroll-down>
@@ -1349,8 +1331,7 @@ after <handle-special-character> [
     move-to-start-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1362,8 +1343,7 @@ after <handle-special-key> [
     move-to-start-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1525,8 +1505,7 @@ after <handle-special-character> [
     move-to-end-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1538,8 +1517,7 @@ after <handle-special-key> [
     move-to-end-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1674,8 +1652,7 @@ after <handle-special-character> [
     <delete-to-start-of-line-begin>
     deleted-cells:&:duplex-list:char <- delete-to-start-of-line editor
     <delete-to-start-of-line-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -1812,8 +1789,7 @@ after <handle-special-character> [
     <delete-to-end-of-line-begin>
     deleted-cells:&:duplex-list:char <- delete-to-end-of-line editor
     <delete-to-end-of-line-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -2003,8 +1979,7 @@ after <scroll-down> [
   top-of-screen <- before-start-of-next-line top-of-screen, max
   *editor <- put *editor, top-of-screen:offset, top-of-screen
   no-movement?:bool <- equal old-top, top-of-screen
-  go-render? <- copy 0/false
-  return-if no-movement?
+  return-if no-movement?, 0/don't-render
 ]
 
 # takes a pointer into the doubly-linked list, scans ahead at most 'max'
@@ -2383,8 +2358,7 @@ after <scroll-up> [
   top-of-screen <- before-previous-line top-of-screen, editor
   *editor <- put *editor, top-of-screen:offset, top-of-screen
   no-movement?:bool <- equal old-top, top-of-screen
-  go-render? <- copy 0/false
-  return-if no-movement?
+  return-if no-movement?, 0/don't-render
 ]
 
 # takes a pointer into the doubly-linked list, scans back to before start of
@@ -2790,9 +2764,8 @@ after <handle-special-character> [
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
     top-of-screen:&:duplex-list:char <- get *editor, top-of-screen:offset
-    no-movement?:bool <- equal top-of-screen, old-top
-    go-render? <- not no-movement?
-    return
+    movement?:bool <- not-equal top-of-screen, old-top
+    return movement?/go-render
   }
 ]
 
@@ -2806,9 +2779,8 @@ after <handle-special-key> [
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
     top-of-screen:&:duplex-list:char <- get *editor, top-of-screen:offset
-    no-movement?:bool <- equal top-of-screen, old-top
-    go-render? <- not no-movement?
-    return
+    movement?:bool <- not-equal top-of-screen, old-top
+    return movement?/go-render
   }
 ]
 
@@ -2991,9 +2963,8 @@ after <handle-special-character> [
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
     top-of-screen:&:duplex-list:char <- get *editor, top-of-screen:offset
-    no-movement?:bool <- equal top-of-screen, old-top
-    go-render? <- not no-movement?
-    return
+    movement?:bool <- not-equal top-of-screen, old-top
+    return movement?/go-render
   }
 ]
 
@@ -3007,10 +2978,9 @@ after <handle-special-key> [
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
     top-of-screen:&:duplex-list:char <- get *editor, top-of-screen:offset
-    no-movement?:bool <- equal top-of-screen, old-top
+    movement?:bool <- not-equal top-of-screen, old-top
     # don't bother re-rendering if nothing changed. todo: test this
-    go-render? <- not no-movement?
-    return
+    return movement?/go-render
   }
 ]
 
diff --git a/edit/004-programming-environment.mu b/edit/004-programming-environment.mu
index 7747e7a1..332b7e18 100644
--- a/edit/004-programming-environment.mu
+++ b/edit/004-programming-environment.mu
@@ -112,7 +112,7 @@ def event-loop screen:&:screen, console:&:console, env:&:environment -> screen:&
       sandbox-in-focus?:bool <- get *env, sandbox-in-focus?:offset
       {
         break-if sandbox-in-focus?
-        screen, recipes, render?:bool <- handle-keyboard-event screen, recipes, e:event
+        render?:bool <- handle-keyboard-event screen, recipes, e:event
         # refresh screen only if no more events
         # if there are more events to process, wait for them to clear up, then make sure you render-all afterward.
         more-events?:bool <- has-more-events? console
@@ -140,7 +140,7 @@ def event-loop screen:&:screen, console:&:console, env:&:environment -> screen:&
       }
       {
         break-unless sandbox-in-focus?
-        screen, current-sandbox, render?:bool <- handle-keyboard-event screen, current-sandbox, e:event
+        render?:bool <- handle-keyboard-event screen, current-sandbox, e:event
         # refresh screen only if no more events
         # if there are more events to process, wait for them to clear up, then make sure you render-all afterward.
         more-events?:bool <- has-more-events? console
diff --git a/edit/012-editor-undo.mu b/edit/012-editor-undo.mu
index c69e6c82..c2f6bca3 100644
--- a/edit/012-editor-undo.mu
+++ b/edit/012-editor-undo.mu
@@ -74,7 +74,7 @@ after <handle-special-character> [
     redo <- push op, redo
     *editor <- put *editor, redo:offset, redo
     <handle-undo>
-    return screen, editor, 1/go-render
+    return 1/go-render
   }
 ]
 
@@ -92,7 +92,7 @@ after <handle-special-character> [
     undo <- push op, undo
     *editor <- put *editor, undo:offset, undo
     <handle-redo>
-    return screen, editor, 1/go-render
+    return 1/go-render
   }
 ]
 
diff --git a/html/edit/002-typing.mu.html b/html/edit/002-typing.mu.html
index 2c52331c..15853c1f 100644
--- a/html/edit/002-typing.mu.html
+++ b/html/edit/002-typing.mu.html
@@ -69,7 +69,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     <span class="Comment"># keyboard events</span>
     <span class="Delimiter">{</span>
       <span class="muControl">break-if</span> is-touch?
-      screen, editor, go-render?:bool <span class="Special">&lt;-</span> handle-keyboard-event screen, editor, e
+      go-render?:bool <span class="Special">&lt;-</span> handle-keyboard-event screen, editor, e
       <span class="Delimiter">{</span>
         <span class="muControl">break-unless</span> go-render?
         screen <span class="Special">&lt;-</span> editor-render screen, editor
@@ -196,11 +196,10 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
 
 <span class="Comment"># Process an event 'e' and try to minimally update the screen.</span>
 <span class="Comment"># Set 'go-render?' to true to indicate the caller must perform a non-minimal update.</span>
-<span class="muRecipe">def</span> handle-keyboard-event screen:&amp;:screen, editor:&amp;:editor, e:event<span class="muRecipe"> -&gt; </span>screen:&amp;:screen, editor:&amp;:editor, go-render?:bool [
+<span class="muRecipe">def</span> handle-keyboard-event screen:&amp;:screen, editor:&amp;:editor, e:event<span class="muRecipe"> -&gt; </span>go-render?:bool, screen:&amp;:screen, editor:&amp;:editor [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-  <span class="muControl">return-unless</span> editor
+  <span class="muControl">return-unless</span> editor, <span class="Constant">0/don't-render</span>
   screen-width:num <span class="Special">&lt;-</span> screen-width screen
   screen-height:num <span class="Special">&lt;-</span> screen-height screen
   left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
@@ -219,11 +218,10 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
 <span class="Constant">    &lt;handle-special-character&gt;</span>
     <span class="Comment"># ignore any other special characters</span>
     regular-character?:bool <span class="Special">&lt;-</span> greater-or-equal c, <span class="Constant">32/space</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return-unless</span> regular-character?
+    <span class="muControl">return-unless</span> regular-character?, <span class="Constant">0/don't-render</span>
     <span class="Comment"># otherwise type it in</span>
 <span class="Constant">    &lt;insert-character-begin&gt;</span>
-    editor, screen, go-render?:bool <span class="Special">&lt;-</span> insert-at-cursor editor, c, screen
+    go-render? <span class="Special">&lt;-</span> insert-at-cursor editor, c, screen
 <span class="Constant">    &lt;insert-character-end&gt;</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
@@ -232,11 +230,10 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   assert is-keycode?, <span class="Constant">[event was of unknown type; neither keyboard nor mouse]</span>
   <span class="Comment"># handlers for each special key will go here</span>
 <span class="Constant">  &lt;handle-special-key&gt;</span>
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-  <span class="muControl">return</span>
+  <span class="muControl">return</span> <span class="Constant">1/go-render</span>
 ]
 
-<span class="muRecipe">def</span> insert-at-cursor editor:&amp;:editor, c:char, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, screen:&amp;:screen, go-render?:bool [
+<span class="muRecipe">def</span> insert-at-cursor editor:&amp;:editor, c:char, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor, screen:&amp;:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   before-cursor:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
@@ -268,8 +265,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     <span class="muControl">break-if</span> overflow?
     move-cursor screen, save-row, save-column
     print screen, c
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># not at right margin? print the character and rest of line</span>
@@ -281,9 +277,8 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     curr-column:num <span class="Special">&lt;-</span> copy save-column
     <span class="Delimiter">{</span>
       <span class="Comment"># hit right margin? give up and let caller render</span>
-      go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
       at-right?:bool <span class="Special">&lt;-</span> greater-than curr-column, right
-      <span class="muControl">return-if</span> at-right?
+      <span class="muControl">return-if</span> at-right?, <span class="Constant">1/go-render</span>
       <span class="muControl">break-unless</span> curr
       <span class="Comment"># newline? done.</span>
       currc:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
@@ -294,11 +289,9 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
       curr <span class="Special">&lt;-</span> next curr
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-  <span class="muControl">return</span>
+  <span class="muControl">return</span> <span class="Constant">1/go-render</span>
 ]
 
 <span class="Comment"># helper for tests</span>
@@ -775,8 +768,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
       <span class="muControl">break-unless</span> below-screen?
 <span class="Constant">      &lt;scroll-down&gt;</span>
     <span class="Delimiter">}</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -898,14 +890,13 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
     <span class="muControl">break-unless</span> newline?
 <span class="Constant">    &lt;insert-enter-begin&gt;</span>
-    editor <span class="Special">&lt;-</span> insert-new-line-and-indent editor, screen
+    insert-new-line-and-indent editor, screen
 <span class="Constant">    &lt;insert-enter-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">def</span> insert-new-line-and-indent editor:&amp;:editor, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, screen:&amp;:screen, go-render?:bool [
+<span class="muRecipe">def</span> insert-new-line-and-indent editor:&amp;:editor, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, screen:&amp;:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
@@ -927,7 +918,6 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, screen-height  <span class="Comment"># must be equal, never greater</span>
     <span class="muControl">break-unless</span> below-screen?
 <span class="Constant">    &lt;scroll-down&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
     cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># bring back into screen range</span>
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
   <span class="Delimiter">}</span>
@@ -941,7 +931,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   <span class="Delimiter">{</span>
     indent-done?:bool <span class="Special">&lt;-</span> greater-or-equal i, indent
     <span class="muControl">break-if</span> indent-done?
-    editor, screen, go-render?:bool <span class="Special">&lt;-</span> insert-at-cursor editor, <span class="Constant">32/space</span>, screen
+    insert-at-cursor editor, <span class="Constant">32/space</span>, screen
     i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
@@ -1083,8 +1073,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     paste-start?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65507/paste-start</span>
     <span class="muControl">break-unless</span> paste-start?
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">indent?:offset</span>, <span class="Constant">0/false</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1093,8 +1082,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     paste-end?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65506/paste-end</span>
     <span class="muControl">break-unless</span> paste-end?
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">indent?:offset</span>, <span class="Constant">1/true</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
diff --git a/html/edit/003-shortcuts.mu.html b/html/edit/003-shortcuts.mu.html
index 9225ac1a..e7b49f49 100644
--- a/html/edit/003-shortcuts.mu.html
+++ b/html/edit/003-shortcuts.mu.html
@@ -63,11 +63,10 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     tab?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">9/tab</span>
     <span class="muControl">break-unless</span> tab?
 <span class="Constant">    &lt;insert-character-begin&gt;</span>
-    editor, screen, go-render?:bool <span class="Special">&lt;-</span> insert-at-cursor editor, <span class="Constant">32/space</span>, screen
-    editor, screen, go-render?:bool <span class="Special">&lt;-</span> insert-at-cursor editor, <span class="Constant">32/space</span>, screen
+    insert-at-cursor editor, <span class="Constant">32/space</span>, screen
+    insert-at-cursor editor, <span class="Constant">32/space</span>, screen
 <span class="Constant">    &lt;insert-character-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -106,7 +105,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     delete-previous-character?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">8/backspace</span>
     <span class="muControl">break-unless</span> delete-previous-character?
 <span class="Constant">    &lt;backspace-character-begin&gt;</span>
-    editor, screen, go-render?:bool, backspaced-cell:&amp;:duplex-list:char <span class="Special">&lt;-</span> delete-before-cursor editor, screen
+    go-render?:bool, backspaced-cell:&amp;:duplex-list:char <span class="Special">&lt;-</span> delete-before-cursor editor, screen
 <span class="Constant">    &lt;backspace-character-end&gt;</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
@@ -115,31 +114,28 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
 <span class="Comment"># return values:</span>
 <span class="Comment">#   go-render? - whether caller needs to update the screen</span>
 <span class="Comment">#   backspaced-cell - value deleted (or 0 if nothing was deleted) so we can save it for undo, etc.</span>
-<span class="muRecipe">def</span> delete-before-cursor editor:&amp;:editor, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, screen:&amp;:screen, go-render?:bool, backspaced-cell:&amp;:duplex-list:char [
+<span class="muRecipe">def</span> delete-before-cursor editor:&amp;:editor, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>go-render?:bool, backspaced-cell:&amp;:duplex-list:char, editor:&amp;:editor, screen:&amp;:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   before-cursor:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
   data:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
   <span class="Comment"># if at start of text (before-cursor at § sentinel), return</span>
   prev:&amp;:duplex-list:char <span class="Special">&lt;-</span> prev before-cursor
-  go-render?, backspaced-cell <span class="Special">&lt;-</span> copy <span class="Constant">0/no-more-render</span>, <span class="Constant">0/nothing-deleted</span>
-  <span class="muControl">return-unless</span> prev
+  <span class="muControl">return-unless</span> prev, <span class="Constant">0/no-more-render</span>, <span class="Constant">0/nothing-deleted</span>
   trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[delete-before-cursor]</span>
   original-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
-  editor, scroll?:bool <span class="Special">&lt;-</span> move-cursor-coordinates-left editor
+  scroll?:bool <span class="Special">&lt;-</span> move-cursor-coordinates-left editor
   backspaced-cell:&amp;:duplex-list:char <span class="Special">&lt;-</span> copy before-cursor
   data <span class="Special">&lt;-</span> remove before-cursor, data  <span class="Comment"># will also neatly trim next/prev pointers in backspaced-cell/before-cursor</span>
   before-cursor <span class="Special">&lt;-</span> copy prev
   *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-  <span class="muControl">return-if</span> scroll?
+  <span class="muControl">return-if</span> scroll?, <span class="Constant">1/go-render</span>
   screen-width:num <span class="Special">&lt;-</span> screen-width screen
   cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
   <span class="Comment"># did we just backspace over a newline?</span>
   same-row?:bool <span class="Special">&lt;-</span> equal cursor-row, original-row
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-  <span class="muControl">return-unless</span> same-row?
+  <span class="muControl">return-unless</span> same-row?, <span class="Constant">1/go-render</span>
   left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
   right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
   curr:&amp;:duplex-list:char <span class="Special">&lt;-</span> next before-cursor
@@ -148,8 +144,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   <span class="Delimiter">{</span>
     <span class="Comment"># hit right margin? give up and let caller render</span>
     at-right?:bool <span class="Special">&lt;-</span> greater-or-equal curr-column, right
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return-if</span> at-right?
+    <span class="muControl">return-if</span> at-right?, <span class="Constant">1/go-render</span>
     <span class="muControl">break-unless</span> curr
     <span class="Comment"># newline? done.</span>
     currc:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
@@ -166,9 +161,10 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
 ]
 
-<span class="muRecipe">def</span> move-cursor-coordinates-left editor:&amp;:editor<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, go-render?:bool [
+<span class="muRecipe">def</span> move-cursor-coordinates-left editor:&amp;:editor<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
+  go-render?:bool <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
   before-cursor:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
   cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
@@ -180,12 +176,10 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[decrementing cursor column]</span>
     cursor-column <span class="Special">&lt;-</span> subtract cursor-column,<span class="Constant"> 1</span>
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># if at left margin, we must move to previous row:</span>
   top-of-screen?:bool <span class="Special">&lt;-</span> equal cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># exclude menu bar</span>
-  go-render?:bool <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-if</span> top-of-screen?
     cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>
@@ -379,25 +373,23 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     delete-next-character?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65522/delete</span>
     <span class="muControl">break-unless</span> delete-next-character?
 <span class="Constant">    &lt;delete-character-begin&gt;</span>
-    editor, screen, go-render?:bool, deleted-cell:&amp;:duplex-list:char <span class="Special">&lt;-</span> delete-at-cursor editor, screen
+    go-render?:bool, deleted-cell:&amp;:duplex-list:char <span class="Special">&lt;-</span> delete-at-cursor editor, screen
 <span class="Constant">    &lt;delete-character-end&gt;</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">def</span> delete-at-cursor editor:&amp;:editor, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, screen:&amp;:screen, go-render?:bool, deleted-cell:&amp;:duplex-list:char [
+<span class="muRecipe">def</span> delete-at-cursor editor:&amp;:editor, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>go-render?:bool, deleted-cell:&amp;:duplex-list:char, editor:&amp;:editor, screen:&amp;:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   before-cursor:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
   data:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
   deleted-cell:&amp;:duplex-list:char <span class="Special">&lt;-</span> next before-cursor
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-  <span class="muControl">return-unless</span> deleted-cell
+  <span class="muControl">return-unless</span> deleted-cell, <span class="Constant">0/don't-render</span>
   currc:char <span class="Special">&lt;-</span> get *deleted-cell, <span class="Constant">value:offset</span>
   data <span class="Special">&lt;-</span> remove deleted-cell, data
   deleted-newline?:bool <span class="Special">&lt;-</span> equal currc, <span class="Constant">10/newline</span>
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-  <span class="muControl">return-if</span> deleted-newline?
+  <span class="muControl">return-if</span> deleted-newline?, <span class="Constant">1/go-render</span>
   <span class="Comment"># wasn't a newline? render rest of line</span>
   curr:&amp;:duplex-list:char <span class="Special">&lt;-</span> next before-cursor  <span class="Comment"># refresh after remove above</span>
   cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
@@ -408,8 +400,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   <span class="Delimiter">{</span>
     <span class="Comment"># hit right margin? give up and let caller render</span>
     at-right?:bool <span class="Special">&lt;-</span> greater-or-equal curr-column, screen-width
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return-if</span> at-right?
+    <span class="muControl">return-if</span> at-right?, <span class="Constant">1/go-render</span>
     <span class="muControl">break-unless</span> curr
     <span class="Comment"># newline? done.</span>
     currc:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
@@ -461,7 +452,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
     before-cursor <span class="Special">&lt;-</span> copy next-cursor
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
-    editor, go-render?:bool <span class="Special">&lt;-</span> move-cursor-coordinates-right editor, screen-height
+    go-render?:bool <span class="Special">&lt;-</span> move-cursor-coordinates-right editor, screen-height
     screen <span class="Special">&lt;-</span> move-cursor screen, cursor-row, cursor-column
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">2/right-arrow</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
@@ -469,7 +460,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">def</span> move-cursor-coordinates-right editor:&amp;:editor, screen-height:num<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, go-render?:bool [
+<span class="muRecipe">def</span> move-cursor-coordinates-right editor:&amp;:editor, screen-height:num<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   before-cursor:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor <span class="Constant">before-cursor:offset</span>
@@ -487,13 +478,11 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     cursor-column <span class="Special">&lt;-</span> copy left
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
     below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, screen-height  <span class="Comment"># must be equal</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return-unless</span> below-screen?
+    <span class="muControl">return-unless</span> below-screen?, <span class="Constant">0/don't-render</span>
 <span class="Constant">    &lt;scroll-down&gt;</span>
     cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># bring back into screen range</span>
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># if the line wraps, move cursor to start of next row</span>
   <span class="Delimiter">{</span>
@@ -512,12 +501,11 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     cursor-column <span class="Special">&lt;-</span> copy left
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
     below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, screen-height  <span class="Comment"># must be equal</span>
-    <span class="muControl">return-unless</span> below-screen?, editor, <span class="Constant">0/no-more-render</span>
+    <span class="muControl">return-unless</span> below-screen?, <span class="Constant">0/no-more-render</span>
 <span class="Constant">    &lt;scroll-down&gt;</span>
     cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># bring back into screen range</span>
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># otherwise move cursor one character right</span>
   cursor-column <span class="Special">&lt;-</span> add cursor-column,<span class="Constant"> 1</span>
@@ -744,10 +732,9 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[left arrow]</span>
     <span class="Comment"># if not at start of text (before-cursor at § sentinel)</span>
     prev:&amp;:duplex-list:char <span class="Special">&lt;-</span> prev before-cursor
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return-unless</span> prev
+    <span class="muControl">return-unless</span> prev, <span class="Constant">0/don't-render</span>
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
-    editor, go-render? <span class="Special">&lt;-</span> move-cursor-coordinates-left editor
+    go-render? <span class="Special">&lt;-</span> move-cursor-coordinates-left editor
     before-cursor <span class="Special">&lt;-</span> copy prev
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">1/left-arrow</span>
@@ -1013,16 +1000,17 @@ d]
     move-to-previous-line?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65517/up-arrow</span>
     <span class="muControl">break-unless</span> move-to-previous-line?
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
-    editor, go-render? <span class="Special">&lt;-</span> move-to-previous-line editor
+    go-render? <span class="Special">&lt;-</span> move-to-previous-line editor
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">3/up-arrow</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">def</span> move-to-previous-line editor:&amp;:editor<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, go-render?:bool [
+<span class="muRecipe">def</span> move-to-previous-line editor:&amp;:editor<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
+  go-render?:bool <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
   cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
   before-cursor:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
@@ -1043,14 +1031,12 @@ d]
       <span class="muControl">break-if</span> at-newline?
       curr:&amp;:duplex-list:char <span class="Special">&lt;-</span> before-previous-line curr, editor
       no-motion?:bool <span class="Special">&lt;-</span> equal curr, old
-      go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
       <span class="muControl">return-if</span> no-motion?
     <span class="Delimiter">}</span>
     <span class="Delimiter">{</span>
       old <span class="Special">&lt;-</span> copy curr
       curr <span class="Special">&lt;-</span> before-previous-line curr, editor
       no-motion?:bool <span class="Special">&lt;-</span> equal curr, old
-      go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
       <span class="muControl">return-if</span> no-motion?
     <span class="Delimiter">}</span>
     before-cursor <span class="Special">&lt;-</span> copy curr
@@ -1076,15 +1062,13 @@ d]
       *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># if cursor already at top, scroll up</span>
     <span class="muControl">break-unless</span> already-at-top?
 <span class="Constant">    &lt;scroll-up&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1247,14 +1231,14 @@ d]
     move-to-next-line?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65516/down-arrow</span>
     <span class="muControl">break-unless</span> move-to-next-line?
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
-    editor, go-render? <span class="Special">&lt;-</span> move-to-next-line editor, screen-height
+    go-render? <span class="Special">&lt;-</span> move-to-next-line editor, screen-height
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">4/down-arrow</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
     <span class="muControl">return</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">def</span> move-to-next-line editor:&amp;:editor, screen-height:num<span class="muRecipe"> -&gt; </span>editor:&amp;:editor, go-render?:bool [
+<span class="muRecipe">def</span> move-to-next-line editor:&amp;:editor, screen-height:num<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
@@ -1277,8 +1261,7 @@ d]
       <span class="muControl">break-unless</span> no-motion?
       scroll?:bool <span class="Special">&lt;-</span> greater-than cursor-row,<span class="Constant"> 1</span>
       <span class="muControl">break-if</span> scroll?, <span class="Constant">+try-to-scroll</span>
-      go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-      <span class="muControl">return</span>
+      <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
     <span class="Delimiter">}</span>
     cursor-row <span class="Special">&lt;-</span> add cursor-row,<span class="Constant"> 1</span>
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
@@ -1302,8 +1285,7 @@ d]
       *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
 <span class="Constant">  +try-to-scroll</span>
 <span class="Constant">  &lt;scroll-down&gt;</span>
@@ -1383,8 +1365,7 @@ d]
     move-to-start-of-line editor
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1396,8 +1377,7 @@ d]
     move-to-start-of-line editor
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1559,8 +1539,7 @@ d]
     move-to-end-of-line editor
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1572,8 +1551,7 @@ d]
     move-to-end-of-line editor
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1708,8 +1686,7 @@ d]
 <span class="Constant">    &lt;delete-to-start-of-line-begin&gt;</span>
     deleted-cells:&amp;:duplex-list:char <span class="Special">&lt;-</span> delete-to-start-of-line editor
 <span class="Constant">    &lt;delete-to-start-of-line-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -1846,8 +1823,7 @@ d]
 <span class="Constant">    &lt;delete-to-end-of-line-begin&gt;</span>
     deleted-cells:&amp;:duplex-list:char <span class="Special">&lt;-</span> delete-to-end-of-line editor
 <span class="Constant">    &lt;delete-to-end-of-line-end&gt;</span>
-    go-render? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -2037,8 +2013,7 @@ d]
   top-of-screen <span class="Special">&lt;-</span> before-start-of-next-line top-of-screen, max
   *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">top-of-screen:offset</span>, top-of-screen
   no-movement?:bool <span class="Special">&lt;-</span> equal old-top, top-of-screen
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-  <span class="muControl">return-if</span> no-movement?
+  <span class="muControl">return-if</span> no-movement?, <span class="Constant">0/don't-render</span>
 ]
 
 <span class="Comment"># takes a pointer into the doubly-linked list, scans ahead at most 'max'</span>
@@ -2417,8 +2392,7 @@ d]
   top-of-screen <span class="Special">&lt;-</span> before-previous-line top-of-screen, editor
   *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">top-of-screen:offset</span>, top-of-screen
   no-movement?:bool <span class="Special">&lt;-</span> equal old-top, top-of-screen
-  go-render? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-  <span class="muControl">return-if</span> no-movement?
+  <span class="muControl">return-if</span> no-movement?, <span class="Constant">0/don't-render</span>
 ]
 
 <span class="Comment"># takes a pointer into the doubly-linked list, scans back to before start of</span>
@@ -2824,9 +2798,8 @@ e]
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
     top-of-screen:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-    no-movement?:bool <span class="Special">&lt;-</span> equal top-of-screen, old-top
-    go-render? <span class="Special">&lt;-</span> not no-movement?
-    <span class="muControl">return</span>
+    movement?:bool <span class="Special">&lt;-</span> not-equal top-of-screen, old-top
+    <span class="muControl">return</span> movement?/go-render
   <span class="Delimiter">}</span>
 ]
 
@@ -2840,9 +2813,8 @@ e]
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
     top-of-screen:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-    no-movement?:bool <span class="Special">&lt;-</span> equal top-of-screen, old-top
-    go-render? <span class="Special">&lt;-</span> not no-movement?
-    <span class="muControl">return</span>
+    movement?:bool <span class="Special">&lt;-</span> not-equal top-of-screen, old-top
+    <span class="muControl">return</span> movement?/go-render
   <span class="Delimiter">}</span>
 ]
 
@@ -3025,9 +2997,8 @@ e]
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
     top-of-screen:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-    no-movement?:bool <span class="Special">&lt;-</span> equal top-of-screen, old-top
-    go-render? <span class="Special">&lt;-</span> not no-movement?
-    <span class="muControl">return</span>
+    movement?:bool <span class="Special">&lt;-</span> not-equal top-of-screen, old-top
+    <span class="muControl">return</span> movement?/go-render
   <span class="Delimiter">}</span>
 ]
 
@@ -3041,10 +3012,9 @@ e]
     undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span class="Constant">    &lt;move-cursor-end&gt;</span>
     top-of-screen:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-    no-movement?:bool <span class="Special">&lt;-</span> equal top-of-screen, old-top
+    movement?:bool <span class="Special">&lt;-</span> not-equal top-of-screen, old-top
     <span class="Comment"># don't bother re-rendering if nothing changed. todo: test this</span>
-    go-render? <span class="Special">&lt;-</span> not no-movement?
-    <span class="muControl">return</span>
+    <span class="muControl">return</span> movement?/go-render
   <span class="Delimiter">}</span>
 ]
 
diff --git a/html/edit/004-programming-environment.mu.html b/html/edit/004-programming-environment.mu.html
index f363ac7e..776c336e 100644
--- a/html/edit/004-programming-environment.mu.html
+++ b/html/edit/004-programming-environment.mu.html
@@ -147,7 +147,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
       sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
       <span class="Delimiter">{</span>
         <span class="muControl">break-if</span> sandbox-in-focus?
-        screen, recipes, render?:bool <span class="Special">&lt;-</span> handle-keyboard-event screen, recipes, e:event
+        render?:bool <span class="Special">&lt;-</span> handle-keyboard-event screen, recipes, e:event
         <span class="Comment"># refresh screen only if no more events</span>
         <span class="Comment"># if there are more events to process, wait for them to clear up, then make sure you render-all afterward.</span>
         more-events?:bool <span class="Special">&lt;-</span> has-more-events? console
@@ -175,7 +175,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
       <span class="Delimiter">}</span>
       <span class="Delimiter">{</span>
         <span class="muControl">break-unless</span> sandbox-in-focus?
-        screen, current-sandbox, render?:bool <span class="Special">&lt;-</span> handle-keyboard-event screen, current-sandbox, e:event
+        render?:bool <span class="Special">&lt;-</span> handle-keyboard-event screen, current-sandbox, e:event
         <span class="Comment"># refresh screen only if no more events</span>
         <span class="Comment"># if there are more events to process, wait for them to clear up, then make sure you render-all afterward.</span>
         more-events?:bool <span class="Special">&lt;-</span> has-more-events? console
diff --git a/html/edit/012-editor-undo.mu.html b/html/edit/012-editor-undo.mu.html
index c0f6d84a..ec4fd7b9 100644
--- a/html/edit/012-editor-undo.mu.html
+++ b/html/edit/012-editor-undo.mu.html
@@ -109,7 +109,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     redo <span class="Special">&lt;-</span> push op, redo
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">redo:offset</span>, redo
 <span class="Constant">    &lt;handle-undo&gt;</span>
-    <span class="muControl">return</span> screen, editor, <span class="Constant">1/go-render</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
@@ -127,7 +127,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     undo <span class="Special">&lt;-</span> push op, undo
     *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">undo:offset</span>, undo
 <span class="Constant">    &lt;handle-redo&gt;</span>
-    <span class="muControl">return</span> screen, editor, <span class="Constant">1/go-render</span>
+    <span class="muControl">return</span> <span class="Constant">1/go-render</span>
   <span class="Delimiter">}</span>
 ]
 
diff --git a/sandbox/002-typing.mu b/sandbox/002-typing.mu
index a584e6a3..4f704f0d 100644
--- a/sandbox/002-typing.mu
+++ b/sandbox/002-typing.mu
@@ -34,7 +34,7 @@ def editor-event-loop screen:&:screen, console:&:console, editor:&:editor -> scr
     # keyboard events
     {
       break-if is-touch?
-      screen, editor, go-render?:bool <- handle-keyboard-event screen, editor, e
+      go-render?:bool <- handle-keyboard-event screen, editor, e
       {
         break-unless go-render?
         screen <- editor-render screen, editor
@@ -161,11 +161,10 @@ def snap-cursor screen:&:screen, editor:&:editor, target-row:num, target-column:
 
 # Process an event 'e' and try to minimally update the screen.
 # Set 'go-render?' to true to indicate the caller must perform a non-minimal update.
-def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> screen:&:screen, editor:&:editor, go-render?:bool [
+def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> go-render?:bool, screen:&:screen, editor:&:editor [
   local-scope
   load-ingredients
-  go-render? <- copy 0/false
-  return-unless editor
+  return-unless editor, 0/don't-render
   screen-width:num <- screen-width screen
   screen-height:num <- screen-height screen
   left:num <- get *editor, left:offset
@@ -184,11 +183,10 @@ def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> screen:&:
     <handle-special-character>
     # ignore any other special characters
     regular-character?:bool <- greater-or-equal c, 32/space
-    go-render? <- copy 0/false
-    return-unless regular-character?
+    return-unless regular-character?, 0/don't-render
     # otherwise type it in
     <insert-character-begin>
-    editor, screen, go-render?:bool <- insert-at-cursor editor, c, screen
+    go-render? <- insert-at-cursor editor, c, screen
     <insert-character-end>
     return
   }
@@ -197,11 +195,10 @@ def handle-keyboard-event screen:&:screen, editor:&:editor, e:event -> screen:&:
   assert is-keycode?, [event was of unknown type; neither keyboard nor mouse]
   # handlers for each special key will go here
   <handle-special-key>
-  go-render? <- copy 1/true
-  return
+  return 1/go-render
 ]
 
-def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool [
+def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> go-render?:bool, editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
@@ -233,8 +230,7 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor
     break-if overflow?
     move-cursor screen, save-row, save-column
     print screen, c
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
   {
     # not at right margin? print the character and rest of line
@@ -246,9 +242,8 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor
     curr-column:num <- copy save-column
     {
       # hit right margin? give up and let caller render
-      go-render? <- copy 1/true
       at-right?:bool <- greater-than curr-column, right
-      return-if at-right?
+      return-if at-right?, 1/go-render
       break-unless curr
       # newline? done.
       currc:char <- get *curr, value:offset
@@ -259,11 +254,9 @@ def insert-at-cursor editor:&:editor, c:char, screen:&:screen -> editor:&:editor
       curr <- next curr
       loop
     }
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
-  go-render? <- copy 1/true
-  return
+  return 1/go-render
 ]
 
 # helper for tests
@@ -740,8 +733,7 @@ after <insert-character-special-case> [
       break-unless below-screen?
       <scroll-down>
     }
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -863,14 +855,13 @@ after <handle-special-character> [
     newline?:bool <- equal c, 10/newline
     break-unless newline?
     <insert-enter-begin>
-    editor <- insert-new-line-and-indent editor, screen
+    insert-new-line-and-indent editor, screen
     <insert-enter-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
-def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool [
+def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   cursor-row:num <- get *editor, cursor-row:offset
@@ -892,7 +883,6 @@ def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:edit
     below-screen?:bool <- greater-or-equal cursor-row, screen-height  # must be equal, never greater
     break-unless below-screen?
     <scroll-down>
-    go-render? <- copy 1/true
     cursor-row <- subtract cursor-row, 1  # bring back into screen range
     *editor <- put *editor, cursor-row:offset, cursor-row
   }
@@ -906,7 +896,7 @@ def insert-new-line-and-indent editor:&:editor, screen:&:screen -> editor:&:edit
   {
     indent-done?:bool <- greater-or-equal i, indent
     break-if indent-done?
-    editor, screen, go-render?:bool <- insert-at-cursor editor, 32/space, screen
+    insert-at-cursor editor, 32/space, screen
     i <- add i, 1
     loop
   }
@@ -1048,8 +1038,7 @@ after <handle-special-key> [
     paste-start?:bool <- equal k, 65507/paste-start
     break-unless paste-start?
     *editor <- put *editor, indent?:offset, 0/false
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -1058,8 +1047,7 @@ after <handle-special-key> [
     paste-end?:bool <- equal k, 65506/paste-end
     break-unless paste-end?
     *editor <- put *editor, indent?:offset, 1/true
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
diff --git a/sandbox/003-shortcuts.mu b/sandbox/003-shortcuts.mu
index d4255704..4ea2b8cd 100644
--- a/sandbox/003-shortcuts.mu
+++ b/sandbox/003-shortcuts.mu
@@ -29,11 +29,10 @@ after <handle-special-character> [
     tab?:bool <- equal c, 9/tab
     break-unless tab?
     <insert-character-begin>
-    editor, screen, go-render?:bool <- insert-at-cursor editor, 32/space, screen
-    editor, screen, go-render?:bool <- insert-at-cursor editor, 32/space, screen
+    insert-at-cursor editor, 32/space, screen
+    insert-at-cursor editor, 32/space, screen
     <insert-character-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -72,7 +71,7 @@ after <handle-special-character> [
     delete-previous-character?:bool <- equal c, 8/backspace
     break-unless delete-previous-character?
     <backspace-character-begin>
-    editor, screen, go-render?:bool, backspaced-cell:&:duplex-list:char <- delete-before-cursor editor, screen
+    go-render?:bool, backspaced-cell:&:duplex-list:char <- delete-before-cursor editor, screen
     <backspace-character-end>
     return
   }
@@ -81,19 +80,17 @@ after <handle-special-character> [
 # return values:
 #   go-render? - whether caller needs to update the screen
 #   backspaced-cell - value deleted (or 0 if nothing was deleted) so we can save it for undo, etc.
-def delete-before-cursor editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool, backspaced-cell:&:duplex-list:char [
+def delete-before-cursor editor:&:editor, screen:&:screen -> go-render?:bool, backspaced-cell:&:duplex-list:char, editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
   data:&:duplex-list:char <- get *editor, data:offset
   # if at start of text (before-cursor at § sentinel), return
   prev:&:duplex-list:char <- prev before-cursor
-  go-render?, backspaced-cell <- copy 0/no-more-render, 0/nothing-deleted
-  return-unless prev
-  go-render? <- copy 1/true
+  return-unless prev, 0/no-more-render, 0/nothing-deleted
   trace 10, [app], [delete-before-cursor]
   original-row:num <- get *editor, cursor-row:offset
-  editor <- move-cursor-coordinates-left editor
+  move-cursor-coordinates-left editor
   backspaced-cell:&:duplex-list:char <- copy before-cursor
   data <- remove before-cursor, data  # will also neatly trim next/prev pointers in backspaced-cell/before-cursor
   before-cursor <- copy prev
@@ -103,7 +100,7 @@ def delete-before-cursor editor:&:editor, screen:&:screen -> editor:&:editor, sc
   cursor-column:num <- get *editor, cursor-column:offset
   # did we just backspace over a newline?
   same-row?:bool <- equal cursor-row, original-row
-  return-unless same-row?
+  return-unless same-row?, 1/go-render
   left:num <- get *editor, left:offset
   right:num <- get *editor, right:offset
   curr:&:duplex-list:char <- next before-cursor
@@ -112,7 +109,7 @@ def delete-before-cursor editor:&:editor, screen:&:screen -> editor:&:editor, sc
   {
     # hit right margin? give up and let caller render
     at-right?:bool <- greater-or-equal curr-column, right
-    return-if at-right?
+    return-if at-right?, 1/go-render
     break-unless curr
     # newline? done.
     currc:char <- get *curr, value:offset
@@ -339,25 +336,23 @@ after <handle-special-key> [
     delete-next-character?:bool <- equal k, 65522/delete
     break-unless delete-next-character?
     <delete-character-begin>
-    editor, screen, go-render?:bool, deleted-cell:&:duplex-list:char <- delete-at-cursor editor, screen
+    go-render?:bool, deleted-cell:&:duplex-list:char <- delete-at-cursor editor, screen
     <delete-character-end>
     return
   }
 ]
 
-def delete-at-cursor editor:&:editor, screen:&:screen -> editor:&:editor, screen:&:screen, go-render?:bool, deleted-cell:&:duplex-list:char [
+def delete-at-cursor editor:&:editor, screen:&:screen -> go-render?:bool, deleted-cell:&:duplex-list:char, editor:&:editor, screen:&:screen [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor, before-cursor:offset
   data:&:duplex-list:char <- get *editor, data:offset
   deleted-cell:&:duplex-list:char <- next before-cursor
-  go-render? <- copy 0/false
-  return-unless deleted-cell
+  return-unless deleted-cell, 0/don't-render
   currc:char <- get *deleted-cell, value:offset
   data <- remove deleted-cell, data
   deleted-newline?:bool <- equal currc, 10/newline
-  go-render? <- copy 1/true
-  return-if deleted-newline?
+  return-if deleted-newline?, 1/go-render
   # wasn't a newline? render rest of line
   curr:&:duplex-list:char <- next before-cursor  # refresh after remove above
   cursor-row:num <- get *editor, cursor-row:offset
@@ -368,8 +363,7 @@ def delete-at-cursor editor:&:editor, screen:&:screen -> editor:&:editor, screen
   {
     # hit right margin? give up and let caller render
     at-right?:bool <- greater-or-equal curr-column, screen-width
-    go-render? <- copy 1/true
-    return-if at-right?
+    return-if at-right?, 1/go-render
     break-unless curr
     # newline? done.
     currc:char <- get *curr, value:offset
@@ -421,7 +415,7 @@ after <handle-special-key> [
     <move-cursor-begin>
     before-cursor <- copy next-cursor
     *editor <- put *editor, before-cursor:offset, before-cursor
-    editor, go-render?:bool <- move-cursor-coordinates-right editor, screen-height
+    go-render?:bool <- move-cursor-coordinates-right editor, screen-height
     screen <- move-cursor screen, cursor-row, cursor-column
     undo-coalesce-tag:num <- copy 2/right-arrow
     <move-cursor-end>
@@ -429,7 +423,7 @@ after <handle-special-key> [
   }
 ]
 
-def move-cursor-coordinates-right editor:&:editor, screen-height:num -> editor:&:editor, go-render?:bool [
+def move-cursor-coordinates-right editor:&:editor, screen-height:num -> go-render?:bool, editor:&:editor [
   local-scope
   load-ingredients
   before-cursor:&:duplex-list:char <- get *editor before-cursor:offset
@@ -447,12 +441,10 @@ def move-cursor-coordinates-right editor:&:editor, screen-height:num -> editor:&
     cursor-column <- copy left
     *editor <- put *editor, cursor-column:offset, cursor-column
     below-screen?:bool <- greater-or-equal cursor-row, screen-height  # must be equal
-    go-render? <- copy 0/false
-    return-unless below-screen?
+    return-unless below-screen?, 0/don't-render
     cursor-row <- subtract cursor-row, 1  # bring back into screen range
     *editor <- put *editor, cursor-row:offset, cursor-row
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
   # if the line wraps, move cursor to start of next row
   {
@@ -471,11 +463,10 @@ def move-cursor-coordinates-right editor:&:editor, screen-height:num -> editor:&
     cursor-column <- copy left
     *editor <- put *editor, cursor-column:offset, cursor-column
     below-screen?:bool <- greater-or-equal cursor-row, screen-height  # must be equal
-    return-unless below-screen?, editor, 0/no-more-render
+    return-unless below-screen?, 0/no-more-render
     cursor-row <- subtract cursor-row, 1  # bring back into screen range
     *editor <- put *editor, cursor-row:offset, cursor-row
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
   # otherwise move cursor one character right
   cursor-column <- add cursor-column, 1
@@ -702,10 +693,9 @@ after <handle-special-key> [
     trace 10, [app], [left arrow]
     # if not at start of text (before-cursor at § sentinel)
     prev:&:duplex-list:char <- prev before-cursor
-    go-render? <- copy 0/false
-    return-unless prev
+    return-unless prev, 0/don't-render
     <move-cursor-begin>
-    editor <- move-cursor-coordinates-left editor
+    move-cursor-coordinates-left editor
     before-cursor <- copy prev
     *editor <- put *editor, before-cursor:offset, before-cursor
     undo-coalesce-tag:num <- copy 1/left-arrow
@@ -971,14 +961,14 @@ after <handle-special-key> [
     move-to-previous-line?:bool <- equal k, 65517/up-arrow
     break-unless move-to-previous-line?
     <move-cursor-begin>
-    editor, go-render? <- move-to-previous-line editor
+    move-to-previous-line editor
     undo-coalesce-tag:num <- copy 3/up-arrow
     <move-cursor-end>
     return
   }
 ]
 
-def move-to-previous-line editor:&:editor -> editor:&:editor, go-render?:bool [
+def move-to-previous-line editor:&:editor -> editor:&:editor [
   local-scope
   load-ingredients
   cursor-row:num <- get *editor, cursor-row:offset
@@ -1001,14 +991,12 @@ def move-to-previous-line editor:&:editor -> editor:&:editor, go-render?:bool [
       break-if at-newline?
       curr:&:duplex-list:char <- before-previous-line curr, editor
       no-motion?:bool <- equal curr, old
-      go-render? <- copy 0/false
       return-if no-motion?
     }
     {
       old <- copy curr
       curr <- before-previous-line curr, editor
       no-motion?:bool <- equal curr, old
-      go-render? <- copy 0/false
       return-if no-motion?
     }
     before-cursor <- copy curr
@@ -1034,14 +1022,6 @@ def move-to-previous-line editor:&:editor -> editor:&:editor, go-render?:bool [
       *editor <- put *editor, cursor-column:offset, cursor-column
       loop
     }
-    go-render? <- copy 0/false
-    return
-  }
-  {
-    # if cursor already at top, do nothing
-    break-unless already-at-top?
-    go-render? <- copy 0/true
-    return
   }
 ]
 
@@ -1326,8 +1306,7 @@ after <handle-special-character> [
     move-to-start-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1339,8 +1318,7 @@ after <handle-special-key> [
     move-to-start-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1502,8 +1480,7 @@ after <handle-special-character> [
     move-to-end-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1515,8 +1492,7 @@ after <handle-special-key> [
     move-to-end-of-line editor
     undo-coalesce-tag:num <- copy 0/never
     <move-cursor-end>
-    go-render? <- copy 0/false
-    return
+    return 0/don't-render
   }
 ]
 
@@ -1651,8 +1627,7 @@ after <handle-special-character> [
     <delete-to-start-of-line-begin>
     deleted-cells:&:duplex-list:char <- delete-to-start-of-line editor
     <delete-to-start-of-line-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
@@ -1789,8 +1764,7 @@ after <handle-special-character> [
     <delete-to-end-of-line-begin>
     deleted-cells:&:duplex-list:char <- delete-to-end-of-line editor
     <delete-to-end-of-line-end>
-    go-render? <- copy 1/true
-    return
+    return 1/go-render
   }
 ]
 
diff --git a/sandbox/004-programming-environment.mu b/sandbox/004-programming-environment.mu
index c32501a6..84898f71 100644
--- a/sandbox/004-programming-environment.mu
+++ b/sandbox/004-programming-environment.mu
@@ -104,7 +104,7 @@ def event-loop screen:&:screen, console:&:console, env:&:environment -> screen:&
     # if it's not global and not a touch event, send to appropriate editor
     {
       hide-screen screen
-      screen, current-sandbox, render?:bool <- handle-keyboard-event screen, current-sandbox, e:event
+      render?:bool <- handle-keyboard-event screen, current-sandbox, e:event
       # refresh screen only if no more events
       # if there are more events to process, wait for them to clear up, then make sure you render-all afterward.
       more-events?:bool <- has-more-events? console
diff --git a/sandbox/012-editor-undo.mu b/sandbox/012-editor-undo.mu
index a3e4956d..bf64cd75 100644
--- a/sandbox/012-editor-undo.mu
+++ b/sandbox/012-editor-undo.mu
@@ -74,7 +74,7 @@ after <handle-special-character> [
     redo <- push op, redo
     *editor <- put *editor, redo:offset, redo
     <handle-undo>
-    return screen, editor, 1/go-render
+    return 1/go-render
   }
 ]
 
@@ -92,7 +92,7 @@ after <handle-special-character> [
     undo <- push op, undo
     *editor <- put *editor, undo:offset, undo
     <handle-redo>
-    return screen, editor, 1/go-render
+    return 1/go-render
   }
 ]
 
-- 
cgit 1.4.1-2-gfad0