shell: move fake screen to sandbox

5 files changed, 86 insertions, 107 deletions

diff --git a/shell/cell.mu b/shell/cell.mu
index b2b302e6..9dfe298b 100644
--- a/shell/cell.mu
+++ b/shell/cell.mu
@@ -135,3 +135,16 @@ fn new-screen _out: (addr handle cell), width: int, height: int {
   var dest-addr/eax: (addr screen) <- lookup *dest-ah
   initialize-screen dest-addr, width, height
 }
+
+fn clear-screen-cell _self-ah: (addr handle cell) {
+  var self-ah/eax: (addr handle cell) <- copy _self-ah
+  var self/eax: (addr cell) <- lookup *self-ah
+  compare self, 0
+  {
+    break-if-!=
+    return
+  }
+  var screen-ah/eax: (addr handle screen) <- get self, screen-data
+  var screen/eax: (addr screen) <- lookup *screen-ah
+  clear-screen screen
+}
diff --git a/shell/evaluate.mu b/shell/evaluate.mu
index 19fe9fdc..2966751e 100644
--- a/shell/evaluate.mu
+++ b/shell/evaluate.mu
@@ -1,6 +1,7 @@
 # env is an alist of ((sym . val) (sym . val) ...)
 # we never modify `in` or `env`
-fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace) {
+# ignore 'screen-cell' on a first reading; it's a hack for sandboxes
+fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace), screen-cell: (addr handle cell) {
   var in/esi: (addr handle cell) <- copy _in
 #?   dump-cell in
 #?   {
@@ -46,7 +47,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
   {
     break-if-!=
     trace-text trace, "eval", "symbol"
-    lookup-symbol in-addr, out, env-h, globals, trace
+    lookup-symbol in-addr, out, env-h, globals, trace, screen-cell
     trace-higher trace
     return
   }
@@ -120,7 +121,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
     rest-ah <- get rest, right
     rest <- lookup *rest-ah
     var second-arg-ah/edx: (addr handle cell) <- get rest, left
-    evaluate second-arg-ah, out, env-h, globals, trace
+    evaluate second-arg-ah, out, env-h, globals, trace, screen-cell
     trace-text trace, "eval", "saving global binding"
     var first-arg/eax: (addr cell) <- lookup *first-arg-ah
     var first-arg-data-ah/eax: (addr handle stream byte) <- get first-arg, text-data
@@ -157,7 +158,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
     var first-arg-ah/ecx: (addr handle cell) <- get rest, left
     var guard-h: (handle cell)
     var guard-ah/esi: (addr handle cell) <- address guard-h
-    evaluate first-arg-ah, guard-ah, env-h, globals, trace
+    evaluate first-arg-ah, guard-ah, env-h, globals, trace, screen-cell
     rest-ah <- get rest, right
     rest <- lookup *rest-ah
     var branch-ah/edi: (addr handle cell) <- get rest, left
@@ -172,7 +173,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
       rest <- lookup *rest-ah
       branch-ah <- get rest, left
     }
-    evaluate branch-ah, out, env-h, globals, trace
+    evaluate branch-ah, out, env-h, globals, trace, screen-cell
     trace-higher trace
     return
   }
@@ -191,7 +192,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
     var curr-out/eax: (addr cell) <- lookup *curr-out-ah
     var left-out-ah/edi: (addr handle cell) <- get curr-out, left
     var left-ah/esi: (addr handle cell) <- get curr, left
-    evaluate left-ah, left-out-ah, env-h, globals, trace
+    evaluate left-ah, left-out-ah, env-h, globals, trace, screen-cell
     #
     curr-out-ah <- get curr-out, right
     var right-ah/eax: (addr handle cell) <- get curr, right
@@ -204,7 +205,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
   var args-ah/edx: (addr handle cell) <- get evaluated-list, right
 #?   dump-cell args-ah
 #?   abort "aaa"
-  apply function-ah, args-ah, out, env-h, globals, trace
+  apply function-ah, args-ah, out, env-h, globals, trace, screen-cell
   trace-higher trace
   # trace "=> " out {{{
   {
@@ -217,7 +218,7 @@ fn evaluate _in: (addr handle cell), out: (addr handle cell), env-h: (handle cel
   # }}}
 }
 
-fn apply _f-ah: (addr handle cell), args-ah: (addr handle cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace) {
+fn apply _f-ah: (addr handle cell), args-ah: (addr handle cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace), screen-cell: (addr handle cell) {
   var f-ah/eax: (addr handle cell) <- copy _f-ah
   var _f/eax: (addr cell) <- lookup *f-ah
   var f/esi: (addr cell) <- copy _f
@@ -256,14 +257,14 @@ fn apply _f-ah: (addr handle cell), args-ah: (addr handle cell), out: (addr hand
     var rest/eax: (addr cell) <- lookup *rest-ah
     var params-ah/ecx: (addr handle cell) <- get rest, left
     var body-ah/eax: (addr handle cell) <- get rest, right
-    apply-function params-ah, args-ah, body-ah, out, env-h, globals, trace
+    apply-function params-ah, args-ah, body-ah, out, env-h, globals, trace, screen-cell
     trace-higher trace
     return
   }
   error trace, "unknown function"
 }
 
-fn apply-function params-ah: (addr handle cell), args-ah: (addr handle cell), _body-ah: (addr handle cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace) {
+fn apply-function params-ah: (addr handle cell), args-ah: (addr handle cell), _body-ah: (addr handle cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace), screen-cell: (addr handle cell) {
   # push bindings for params to env
   var new-env-storage: (handle cell)
   var new-env-ah/esi: (addr handle cell) <- address new-env-storage
@@ -281,7 +282,7 @@ fn apply-function params-ah: (addr handle cell), args-ah: (addr handle cell), _b
     # evaluate each expression, writing result to `out`
     {
       var curr-ah/eax: (addr handle cell) <- get body, left
-      evaluate curr-ah, out, *new-env-ah, globals, trace
+      evaluate curr-ah, out, *new-env-ah, globals, trace, screen-cell
     }
     #
     body-ah <- get body, right
@@ -374,7 +375,7 @@ fn push-bindings _params-ah: (addr handle cell), _args-ah: (addr handle cell), o
   trace-higher trace
 }
 
-fn lookup-symbol sym: (addr cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace) {
+fn lookup-symbol sym: (addr cell), out: (addr handle cell), env-h: (handle cell), globals: (addr global-table), trace: (addr trace), screen-cell: (addr handle cell) {
   # trace sym
   {
     var stream-storage: (stream byte 0x40)
@@ -407,7 +408,7 @@ fn lookup-symbol sym: (addr cell), out: (addr handle cell), env-h: (handle cell)
     var env-nil?/eax: boolean <- nil? env
     compare env-nil?, 0/false
     break-if-=
-    lookup-symbol-in-globals sym, out, globals, trace
+    lookup-symbol-in-globals sym, out, globals, trace, screen-cell
     trace-higher trace
     # trace "=> " out " (global)" {{{
     {
@@ -479,7 +480,7 @@ fn lookup-symbol sym: (addr cell), out: (addr handle cell), env-h: (handle cell)
   var env-tail-storage: (handle cell)
   var env-tail-ah/eax: (addr handle cell) <- address env-tail-storage
   cdr env, env-tail-ah, trace
-  lookup-symbol sym, out, *env-tail-ah, globals, trace
+  lookup-symbol sym, out, *env-tail-ah, globals, trace, screen-cell
   trace-higher trace
     # trace "=> " out " (recurse)" {{{
     {
@@ -517,7 +518,7 @@ fn test-lookup-symbol-in-env {
   var tmp-ah/edx: (addr handle cell) <- address tmp-storage
   new-symbol tmp-ah, "a"
   var in/eax: (addr cell) <- lookup *tmp-ah
-  lookup-symbol in, tmp-ah, *env-ah, 0/no-globals, 0/no-trace
+  lookup-symbol in, tmp-ah, *env-ah, 0/no-globals, 0/no-trace, 0/no-screen
   var result/eax: (addr cell) <- lookup *tmp-ah
   var result-type/edx: (addr int) <- get result, type
   check-ints-equal *result-type, 1/number, "F - test-lookup-symbol-in-env/0"
@@ -539,7 +540,7 @@ fn test-lookup-symbol-in-globals {
   var tmp-ah/ebx: (addr handle cell) <- address tmp-storage
   new-symbol tmp-ah, "+"
   var in/eax: (addr cell) <- lookup *tmp-ah
-  lookup-symbol in, tmp-ah, *nil-ah, globals, 0/no-trace
+  lookup-symbol in, tmp-ah, *nil-ah, globals, 0/no-trace, 0/no-screen
   var result/eax: (addr cell) <- lookup *tmp-ah
   var result-type/edx: (addr int) <- get result, type
   check-ints-equal *result-type, 4/primitive-function, "F - test-lookup-symbol-in-globals/0"
@@ -754,7 +755,7 @@ fn test-evaluate-is-well-behaved {
   var tmp-storage: (handle cell)
   var tmp-ah/edx: (addr handle cell) <- address tmp-storage
   new-symbol tmp-ah, "a"
-  evaluate tmp-ah, tmp-ah, *env-ah, 0/no-globals, t
+  evaluate tmp-ah, tmp-ah, *env-ah, 0/no-globals, t, 0/no-screen
   # doesn't die
   check-trace-contains t, "error", "unbound symbol: a", "F - test-evaluate-is-well-behaved"
 }
@@ -768,7 +769,7 @@ fn test-evaluate-number {
   var tmp-storage: (handle cell)
   var tmp-ah/edx: (addr handle cell) <- address tmp-storage
   new-integer tmp-ah, 3
-  evaluate tmp-ah, tmp-ah, *env-ah, 0/no-globals, 0/no-trace
+  evaluate tmp-ah, tmp-ah, *env-ah, 0/no-globals, 0/no-trace, 0/no-screen
   #
   var result/eax: (addr cell) <- lookup *tmp-ah
   var result-type/edx: (addr int) <- get result, type
@@ -798,7 +799,7 @@ fn test-evaluate-symbol {
   var tmp-storage: (handle cell)
   var tmp-ah/edx: (addr handle cell) <- address tmp-storage
   new-symbol tmp-ah, "a"
-  evaluate tmp-ah, tmp-ah, *env-ah, 0/no-globals, 0/no-trace
+  evaluate tmp-ah, tmp-ah, *env-ah, 0/no-globals, 0/no-trace, 0/no-screen
   var result/eax: (addr cell) <- lookup *tmp-ah
   var result-type/edx: (addr int) <- get result, type
   check-ints-equal *result-type, 1/number, "F - test-evaluate-symbol/0"
@@ -820,7 +821,7 @@ fn test-evaluate-primitive-function {
   # eval +, nil env
   var tmp-storage: (handle cell)
   var tmp-ah/esi: (addr handle cell) <- address tmp-storage
-  evaluate add-ah, tmp-ah, *nil-ah, globals, 0/no-trace
+  evaluate add-ah, tmp-ah, *nil-ah, globals, 0/no-trace, 0/no-screen
   #
   var result/eax: (addr cell) <- lookup *tmp-ah
   var result-type/edx: (addr int) <- get result, type
@@ -855,7 +856,7 @@ fn test-evaluate-primitive-function-call {
   var globals/edx: (addr global-table) <- address globals-storage
   initialize-globals globals
   #
-  evaluate tmp-ah, tmp-ah, *nil-ah, globals, t
+  evaluate tmp-ah, tmp-ah, *nil-ah, globals, t, 0/no-screen
 #?   dump-trace t
   #
   var result/eax: (addr cell) <- lookup *tmp-ah
diff --git a/shell/global.mu b/shell/global.mu
index a3ec33a0..68b584ea 100644
--- a/shell/global.mu
+++ b/shell/global.mu
@@ -22,11 +22,6 @@ fn initialize-globals _self: (addr global-table) {
   append-primitive self, "cons"
   append-primitive self, "="
   append-primitive self, "print"
-  # TODO: isolate screens per-sandbox
-  var screen-storage: (handle cell)
-  var screen-ah/ecx: (addr handle cell) <- address screen-storage
-  new-screen screen-ah, 5/width, 4/height
-  append-global self, "screen", *screen-ah
 }
 
 fn render-globals screen: (addr screen), _self: (addr global-table), xmin: int, ymin: int, xmax: int, ymax: int {
@@ -48,15 +43,10 @@ fn render-globals screen: (addr screen), _self: (addr global-table), xmin: int,
     var curr-name-ah/eax: (addr handle array byte) <- get curr, name
     var _curr-name/eax: (addr array byte) <- lookup *curr-name-ah
     var curr-name/ebx: (addr array byte) <- copy _curr-name
-    {
-      var skip?/eax: boolean <- string-equal? curr-name, "screen"
-      compare skip?, 0/false
-      break-if-!=
-      var tmpx/eax: int <- copy x
-      tmpx <- draw-text-rightward screen, curr-name, tmpx, xmax, bottom-line, 0x2a/fg=orange, 0x12/bg=almost-black
-      tmpx <- draw-text-rightward screen, " ", tmpx, xmax, bottom-line, 7/fg=grey, 0x12/bg=almost-black
-      x <- copy tmpx
-    }
+    var tmpx/eax: int <- copy x
+    tmpx <- draw-text-rightward screen, curr-name, tmpx, xmax, bottom-line, 0x2a/fg=orange, 0x12/bg=almost-black
+    tmpx <- draw-text-rightward screen, " ", tmpx, xmax, bottom-line, 7/fg=grey, 0x12/bg=almost-black
+    x <- copy tmpx
     curr-index <- increment
     loop
   }
@@ -77,9 +67,6 @@ fn render-globals screen: (addr screen), _self: (addr global-table), xmin: int,
       var curr-name-ah/eax: (addr handle array byte) <- get curr, name
       var _curr-name/eax: (addr array byte) <- lookup *curr-name-ah
       var curr-name/edx: (addr array byte) <- copy _curr-name
-      var skip?/eax: boolean <- string-equal? curr-name, "screen"
-      compare skip?, 0/false
-      break-if-!=
       var x/eax: int <- copy xmin
       x, y <- draw-text-wrapping-right-then-down screen, curr-name, xmin, ymin, xmax, ymax, x, y, 0x2a/fg=orange, 0x12/bg=almost-black
       x, y <- draw-text-wrapping-right-then-down screen, " <- ", xmin, ymin, xmax, ymax, x, y, 7/fg=grey, 0x12/bg=almost-black
@@ -143,7 +130,7 @@ fn append-global _self: (addr global-table), name: (addr array byte), value: (ha
   copy-handle value, curr-value-ah
 }
 
-fn lookup-symbol-in-globals _sym: (addr cell), out: (addr handle cell), _globals: (addr global-table), trace: (addr trace) {
+fn lookup-symbol-in-globals _sym: (addr cell), out: (addr handle cell), _globals: (addr global-table), trace: (addr trace), screen-cell: (addr handle cell) {
   var sym/eax: (addr cell) <- copy _sym
   var sym-name-ah/eax: (addr handle stream byte) <- get sym, text-data
   var _sym-name/eax: (addr stream byte) <- lookup *sym-name-ah
@@ -163,6 +150,16 @@ fn lookup-symbol-in-globals _sym: (addr cell), out: (addr handle cell), _globals
     copy-object curr-value, out
     return
   }
+  # if sym is "screen" and screen-cell exists, return it
+  {
+    var sym-is-screen?/eax: boolean <- stream-data-equal? sym-name, "screen"
+    compare sym-is-screen?, 0/false
+    break-if-=
+    compare screen-cell, 0
+    break-if-=
+    copy-object screen-cell, out
+    return
+  }
   # otherwise error "unbound symbol: ", sym
   var stream-storage: (stream byte 0x40)
   var stream/ecx: (addr stream byte) <- address stream-storage
@@ -668,31 +665,3 @@ fn apply-print _args-ah: (addr handle cell), out: (addr handle cell), env-h: (ha
   # return what was printed
   copy-object second-ah, out
 }
-
-fn clear-screen-var _globals: (addr global-table) {
-  var globals/esi: (addr global-table) <- copy _globals
-  var screen-literal-storage: (stream byte 8)
-  var screen-literal/eax: (addr stream byte) <- address screen-literal-storage
-  write screen-literal, "screen"
-  var screen-index/ecx: int <- find-symbol-in-globals globals, screen-literal
-  compare screen-index, -1/not-found
-  {
-    break-if-!=
-    return
-  }
-  var global-data-ah/eax: (addr handle array global) <- get globals, data
-  var global-data/eax: (addr array global) <- lookup *global-data-ah
-  var screen-offset/ecx: (offset global) <- compute-offset global-data, screen-index
-  var screen-global/eax: (addr global) <- index global-data, screen-offset
-  var screen-cell-ah/eax: (addr handle cell) <- get screen-global, value
-  var screen-cell/eax: (addr cell) <- lookup *screen-cell-ah
-  var screen-cell-type/ecx: (addr int) <- get screen-cell, type
-  compare *screen-cell-type, 5/screen
-  {
-    break-if-=
-    return
-  }
-  var screen-ah/eax: (addr handle screen) <- get screen-cell, screen-data
-  var screen/eax: (addr screen) <- lookup *screen-ah
-  clear-screen screen
-}
diff --git a/shell/main.mu b/shell/main.mu
index 733091d1..a19bcead 100644
--- a/shell/main.mu
+++ b/shell/main.mu
@@ -7,7 +7,7 @@ fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk)
   initialize-globals globals
   var sandbox-storage: sandbox
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
-  initialize-sandbox sandbox
+  initialize-sandbox sandbox, 1/with-screen
   load-sandbox data-disk, sandbox
   {
     render-globals screen, globals, 0/x, 0/y, 0x40/xmax, 0x2f/screen-height-without-menu
diff --git a/shell/sandbox.mu b/shell/sandbox.mu
index 2b68de5d..f39c9d24 100644
--- a/shell/sandbox.mu
+++ b/shell/sandbox.mu
@@ -1,18 +1,28 @@
 type sandbox {
   data: (handle gap-buffer)
   value: (handle stream byte)
+  screen-var: (handle cell)
   trace: (handle trace)
   cursor-in-trace?: boolean
 }
 
-fn initialize-sandbox _self: (addr sandbox) {
+fn initialize-sandbox _self: (addr sandbox), screen?: boolean {
   var self/esi: (addr sandbox) <- copy _self
   var data-ah/eax: (addr handle gap-buffer) <- get self, data
   allocate data-ah
   var data/eax: (addr gap-buffer) <- lookup *data-ah
   initialize-gap-buffer data, 0x1000/4KB
+  #
   var value-ah/eax: (addr handle stream byte) <- get self, value
   populate-stream value-ah, 0x1000/4KB
+  #
+  {
+    compare screen?, 0/false
+    break-if-=
+    var screen-ah/eax: (addr handle cell) <- get self, screen-var
+    new-screen screen-ah, 5/width, 4/height
+  }
+  #
   var trace-ah/eax: (addr handle trace) <- get self, trace
   allocate trace-ah
   var trace/eax: (addr trace) <- lookup *trace-ah
@@ -47,7 +57,7 @@ fn render-sandbox screen: (addr screen), _self: (addr sandbox), xmin: int, ymin:
   var data/edx: (addr gap-buffer) <- copy _data
   var x/eax: int <- copy xmin
   var y/ecx: int <- copy ymin
-  y <- maybe-render-empty-screen screen, globals, xmin, y
+  y <- maybe-render-empty-screen screen, self, xmin, y
   var cursor-in-sandbox?/ebx: boolean <- copy 0/false
   {
     var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
@@ -78,7 +88,7 @@ fn render-sandbox screen: (addr screen), _self: (addr sandbox), xmin: int, ymin:
     var dummy/eax: int <- draw-stream-rightward screen, value, x2, xmax, y, 7/fg=grey, 0/bg
   }
   y <- add 2  # padding
-  y <- maybe-render-screen screen, globals, xmin, y
+  y <- maybe-render-screen screen, self, xmin, y
   # render menu
   var cursor-in-trace?/eax: (addr boolean) <- get self, cursor-in-trace?
   compare *cursor-in-trace?, 0/false
@@ -90,23 +100,15 @@ fn render-sandbox screen: (addr screen), _self: (addr sandbox), xmin: int, ymin:
   render-sandbox-menu screen
 }
 
-fn maybe-render-empty-screen screen: (addr screen), _globals: (addr global-table), xmin: int, ymin: int -> _/ecx: int {
-  var globals/esi: (addr global-table) <- copy _globals
-  var screen-literal-storage: (stream byte 8)
-  var screen-literal/eax: (addr stream byte) <- address screen-literal-storage
-  write screen-literal, "screen"
-  var screen-obj-index/ecx: int <- find-symbol-in-globals globals, screen-literal
-  compare screen-obj-index, -1/not-found
+fn maybe-render-empty-screen screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int -> _/ecx: int {
+  var self/esi: (addr sandbox) <- copy _self
+  var screen-obj-cell-ah/eax: (addr handle cell) <- get self, screen-var
+  var screen-obj-cell/eax: (addr cell) <- lookup *screen-obj-cell-ah
+  compare screen-obj-cell, 0
   {
     break-if-!=
     return ymin
   }
-  var global-data-ah/eax: (addr handle array global) <- get globals, data
-  var global-data/eax: (addr array global) <- lookup *global-data-ah
-  var screen-obj-offset/ecx: (offset global) <- compute-offset global-data, screen-obj-index
-  var screen-global/eax: (addr global) <- index global-data, screen-obj-offset
-  var screen-obj-cell-ah/eax: (addr handle cell) <- get screen-global, value
-  var screen-obj-cell/eax: (addr cell) <- lookup *screen-obj-cell-ah
   var screen-obj-cell-type/ecx: (addr int) <- get screen-obj-cell, type
   compare *screen-obj-cell-type, 5/screen
   {
@@ -123,23 +125,15 @@ fn maybe-render-empty-screen screen: (addr screen), _globals: (addr global-table
   return y
 }
 
-fn maybe-render-screen screen: (addr screen), _globals: (addr global-table), xmin: int, ymin: int -> _/ecx: int {
-  var globals/esi: (addr global-table) <- copy _globals
-  var screen-literal-storage: (stream byte 8)
-  var screen-literal/eax: (addr stream byte) <- address screen-literal-storage
-  write screen-literal, "screen"
-  var screen-obj-index/ecx: int <- find-symbol-in-globals globals, screen-literal
-  compare screen-obj-index, -1/not-found
+fn maybe-render-screen screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int -> _/ecx: int {
+  var self/esi: (addr sandbox) <- copy _self
+  var screen-obj-cell-ah/eax: (addr handle cell) <- get self, screen-var
+  var screen-obj-cell/eax: (addr cell) <- lookup *screen-obj-cell-ah
+  compare screen-obj-cell, 0
   {
     break-if-!=
     return ymin
   }
-  var global-data-ah/eax: (addr handle array global) <- get globals, data
-  var global-data/eax: (addr array global) <- lookup *global-data-ah
-  var screen-obj-offset/ecx: (offset global) <- compute-offset global-data, screen-obj-index
-  var screen-global/eax: (addr global) <- index global-data, screen-obj-offset
-  var screen-obj-cell-ah/eax: (addr handle cell) <- get screen-global, value
-  var screen-obj-cell/eax: (addr cell) <- lookup *screen-obj-cell-ah
   var screen-obj-cell-type/ecx: (addr int) <- get screen-obj-cell, type
   compare *screen-obj-cell-type, 5/screen
   {
@@ -347,10 +341,12 @@ fn edit-sandbox _self: (addr sandbox), key: byte, globals: (addr global-table),
     var _value/eax: (addr stream byte) <- lookup *value-ah
     var value/edx: (addr stream byte) <- copy _value
     var trace-ah/eax: (addr handle trace) <- get self, trace
-    var trace/eax: (addr trace) <- lookup *trace-ah
+    var _trace/eax: (addr trace) <- lookup *trace-ah
+    var trace/ebx: (addr trace) <- copy _trace
     clear-trace trace
-    clear-screen-var globals
-    run data, value, globals, trace
+    var screen-cell/eax: (addr handle cell) <- get self, screen-var
+    clear-screen-cell screen-cell
+    run data, value, globals, trace, screen-cell
     return
   }
   # tab
@@ -385,7 +381,7 @@ fn edit-sandbox _self: (addr sandbox), key: byte, globals: (addr global-table),
   return
 }
 
-fn run in: (addr gap-buffer), out: (addr stream byte), globals: (addr global-table), trace: (addr trace) {
+fn run in: (addr gap-buffer), out: (addr stream byte), globals: (addr global-table), trace: (addr trace), screen-cell: (addr handle cell) {
   var read-result-storage: (handle cell)
   var read-result/esi: (addr handle cell) <- address read-result-storage
   read-cell in, read-result, trace
@@ -400,7 +396,7 @@ fn run in: (addr gap-buffer), out: (addr stream byte), globals: (addr global-tab
   allocate-pair nil-ah
   var eval-result-storage: (handle cell)
   var eval-result/edi: (addr handle cell) <- address eval-result-storage
-  evaluate read-result, eval-result, *nil-ah, globals, trace
+  evaluate read-result, eval-result, *nil-ah, globals, trace, screen-cell
   var error?/eax: boolean <- has-errors? trace
   {
     compare error?, 0/false
@@ -415,7 +411,7 @@ fn run in: (addr gap-buffer), out: (addr stream byte), globals: (addr global-tab
 fn test-run-integer {
   var sandbox-storage: sandbox
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
-  initialize-sandbox sandbox
+  initialize-sandbox sandbox, 0/no-screen
   # type "1"
   edit-sandbox sandbox, 0x31/1, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
   # eval
@@ -434,7 +430,7 @@ fn test-run-integer {
 fn test-run-with-spaces {
   var sandbox-storage: sandbox
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
-  initialize-sandbox sandbox
+  initialize-sandbox sandbox, 0/no-screen
   # type input with whitespace before and after
   edit-sandbox sandbox, 0x20/space, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
   edit-sandbox sandbox, 0x31/1, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
@@ -457,7 +453,7 @@ fn test-run-with-spaces {
 fn test-run-quote {
   var sandbox-storage: sandbox
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
-  initialize-sandbox sandbox
+  initialize-sandbox sandbox, 0/no-screen
   # type "'a"
   edit-sandbox sandbox, 0x27/quote, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
   edit-sandbox sandbox, 0x61/a, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
@@ -477,7 +473,7 @@ fn test-run-quote {
 fn test-run-error-invalid-integer {
   var sandbox-storage: sandbox
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
-  initialize-sandbox sandbox
+  initialize-sandbox sandbox, 0/no-screen
   # type "1a"
   edit-sandbox sandbox, 0x31/1, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
   edit-sandbox sandbox, 0x61/a, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
@@ -497,7 +493,7 @@ fn test-run-error-invalid-integer {
 fn test-run-move-cursor-into-trace {
   var sandbox-storage: sandbox
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
-  initialize-sandbox sandbox
+  initialize-sandbox sandbox, 0/no-screen
   # type "12"
   edit-sandbox sandbox, 0x31/1, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk
   edit-sandbox sandbox, 0x32/2, 0/no-globals, 0/no-screen, 0/no-keyboard, 0/no-disk