2135 - bugfix: couldn't see warnings sometimes

I'm starting to feel the need for separating labels to jump to (so must
be unique per recipe) from labels you can tangle at (need not be
unique). Maybe just use a sigil different from '+'?

1 files changed, 49 insertions, 16 deletions

diff --git a/edit.mu b/edit.mu
index c210f4a1..a9c87114 100644
--- a/edit.mu
+++ b/edit.mu
@@ -2671,13 +2671,20 @@ recipe move-to-next-line [
   last-line:number <- subtract screen-height, 1
   already-at-bottom?:boolean <- greater-or-equal *cursor-row, last-line
   {
-    # if cursor not at top, move it
+    # if cursor not at bottom, move it
     break-if already-at-bottom?
     # scan to start of next line, then to right column or until end of line
     max:number <- subtract right, left
     next-line:address:duplex-list <- before-start-of-next-line *before-cursor, max
-    no-motion?:boolean <- equal next-line, *before-cursor
-    reply-if no-motion?, editor/same-as-ingredient:0, 0/no-more-render
+    {
+      # already at end of buffer? try to scroll up (so we can see more
+      # warnings or sandboxes below)
+      no-motion?:boolean <- equal next-line, *before-cursor
+      break-unless no-motion?
+      scroll?:boolean <- greater-than *cursor-row, 1
+      break-if scroll?, +try-to-scroll:label
+      reply editor/same-as-ingredient:0, 0/no-more-render
+    }
     *cursor-row <- add *cursor-row, 1
     *before-cursor <- copy next-line
     target-column:number <- copy *cursor-column
@@ -2697,12 +2704,9 @@ recipe move-to-next-line [
     }
     reply editor/same-as-ingredient:0, 0/no-more-render
   }
-  {
-    # if cursor already at top, scroll up
-    break-unless already-at-bottom?
-    +scroll-down
-    reply editor/same-as-ingredient:0, 1/go-render
-  }
+  +try-to-scroll
+  +scroll-down
+  reply editor/same-as-ingredient:0, 1/go-render
 ]
 
 scenario editor-adjusts-column-at-next-line [
@@ -2741,13 +2745,14 @@ de]
   ]
 ]
 
-scenario editor-stops-at-end-on-down-arrow [
+scenario editor-scrolls-at-end-on-down-arrow [
   assume-screen 10/width, 5/height
   1:address:array:character <- new [abc
 de]
   2:address:editor-data <- new-editor 1:address:array:character, screen:address, 0/left, 10/right
   editor-render screen, 2:address:editor-data
   $clear-trace
+  # try to move down past end of text
   assume-console [
     left-click 2, 0
     press down-arrow
@@ -2757,11 +2762,11 @@ de]
     3:number <- get *2:address:editor-data, cursor-row:offset
     4:number <- get *2:address:editor-data, cursor-column:offset
   ]
+  # screen should scroll, moving cursor to end of text
   memory-should-contain [
-    3 <- 2
-    4 <- 0
+    3 <- 1
+    4 <- 2
   ]
-  check-trace-count-for-label 0, [print-character]
   assume-console [
     type [0]
   ]
@@ -2770,8 +2775,36 @@ de]
   ]
   screen-should-contain [
     .          .
-    .abc       .
-    .0de       .
+    .de0       .
+    .┈┈┈┈┈┈┈┈┈┈.
+    .          .
+  ]
+  # try to move down again
+  $clear-trace
+  assume-console [
+    left-click 2, 0
+    press down-arrow
+  ]
+  run [
+    editor-event-loop screen:address, console:address, 2:address:editor-data
+    3:number <- get *2:address:editor-data, cursor-row:offset
+    4:number <- get *2:address:editor-data, cursor-column:offset
+  ]
+  # screen stops scrolling because cursor is already at top
+  memory-should-contain [
+    3 <- 1
+    4 <- 3
+  ]
+  check-trace-count-for-label 0, [print-character]
+  assume-console [
+    type [1]
+  ]
+  run [
+    editor-event-loop screen:address, console:address, 2:address:editor-data
+  ]
+  screen-should-contain [
+    .          .
+    .de01      .
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
@@ -3440,7 +3473,7 @@ after +scroll-down [
   *top-of-screen <- before-start-of-next-line *top-of-screen, max
   no-movement?:boolean <- equal old-top, *top-of-screen
   # Hack: this reply doesn't match one of the locations of +scroll-down, directly
-  # within insert-at-cursor. however, I'm unable to trigger the error..
+  # within insert-at-cursor. However, I'm unable to trigger the error..
   # If necessary create a duplicate copy of +scroll-down with the right
   # 'reply-if'.
   reply-if no-movement?, editor/same-as-ingredient:0, 0/no-more-render