4 files changed, 61 insertions, 5 deletions
diff --git a/500text-screen.mu b/500text-screen.mu
index 0fd7ae9d..92ea1d2f 100644
--- a/500text-screen.mu
+++ b/500text-screen.mu
@@ -221,6 +221,36 @@ fn clear-screen screen: (addr screen) {
   set-cursor-position screen, 0, 0
 }
 
+fn clear-rect screen: (addr screen), xmin: int, ymin: int, xmax: int, ymax: int, background-color: int {
+  {
+    compare screen, 0
+    break-if-!=
+    clear-rect-on-real-screen xmin, ymin, xmax, ymax, background-color
+    return
+  }
+  # fake screen
+  set-cursor-position screen, 0, 0
+  var screen-addr/esi: (addr screen) <- copy screen
+  var y/eax: int <- copy ymin
+  var ymax/ecx: int <- copy ymax
+  {
+    compare y, ymax
+    break-if->=
+    var x/edx: int <- copy xmin
+    var xmax/ebx: int <- copy xmax
+    {
+      compare x, xmax
+      break-if->=
+      draw-code-point screen, 0x20/space, x, y, 0/fg, background-color
+      x <- increment
+      loop
+    }
+    y <- increment
+    loop
+  }
+  set-cursor-position screen, 0, 0
+}
+
 # there's no grapheme that guarantees to cover every pixel, so we'll bump down
 # to pixels for a real screen
 fn clear-real-screen {
@@ -241,6 +271,30 @@ fn clear-real-screen {
   }
 }
 
+fn clear-rect-on-real-screen xmin: int, ymin: int, xmax: int, ymax: int, background-color: int {
+  var y/eax: int <- copy ymin
+  y <- shift-left 4/log-font-height
+  var ymax/ecx: int <- copy ymax
+  ymax <- shift-left 4/log-font-height
+  {
+    compare y, ymax
+    break-if->=
+    var x/edx: int <- copy xmin
+    x <- shift-left 3/log-font-width
+    var xmax/ebx: int <- copy xmax
+    xmax <- shift-left 3/log-font-width
+    {
+      compare x, xmax
+      break-if->=
+      pixel-on-real-screen x, y, background-color
+      x <- increment
+      loop
+    }
+    y <- increment
+    loop
+  }
+}
+
 fn screen-grapheme-at screen-on-stack: (addr screen), x: int, y: int -> _/eax: grapheme {
   var screen-addr/esi: (addr screen) <- copy screen-on-stack
   var idx/ecx: int <- screen-cell-index screen-addr, x, y
diff --git a/shell/global.mu b/shell/global.mu
index c87198ee..32142633 100644
--- a/shell/global.mu
+++ b/shell/global.mu
@@ -22,6 +22,10 @@ fn initialize-globals _self: (addr global-table) {
   append-primitive self, "cons"
 }
 
+fn render-globals screen: (addr screen), _self: (addr global-table), xmin: int, ymin: int, xmax: int, ymax: int {
+  clear-rect screen, xmin, ymin, xmax, ymax, 0x12/bg=grey
+}
+
 fn append-primitive _self: (addr global-table), name: (addr array byte) {
   var self/esi: (addr global-table) <- copy _self
   var final-index-addr/ecx: (addr int) <- get self, final-index
diff --git a/shell/main.mu b/shell/main.mu
index 29c815dc..04f64011 100644
--- a/shell/main.mu
+++ b/shell/main.mu
@@ -9,11 +9,9 @@ fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk)
   var sandbox/esi: (addr sandbox) <- address sandbox-storage
   initialize-sandbox sandbox
   load-sandbox data-disk, sandbox
-  var width/eax: int <- copy 0
-  var height/ecx: int <- copy 0
-  width, height <- screen-size screen
   {
-    render-sandbox screen, sandbox, 2/x, 2/y, width, height
+    render-globals screen, globals, 0/x, 0/y, 0x40/xmax, 0x30/screen-height
+    render-sandbox screen, sandbox, 0x40/x, 0/y, 0x80/screen-width, 0x30/screen-height
     {
       var key/eax: byte <- read-key keyboard
       compare key, 0
diff --git a/shell/sandbox.mu b/shell/sandbox.mu
index 2b612a13..06bf3656 100644
--- a/shell/sandbox.mu
+++ b/shell/sandbox.mu
@@ -39,7 +39,7 @@ fn allocate-sandbox-with _out: (addr handle sandbox), s: (addr array byte) {
 ##
 
 fn render-sandbox screen: (addr screen), _self: (addr sandbox), xmin: int, ymin: int, xmax: int, ymax: int {
-  clear-screen screen
+  clear-rect screen, xmin, ymin, xmax, ymax, 0/bg=black
   var self/esi: (addr sandbox) <- copy _self
   # data
   var data-ah/eax: (addr handle gap-buffer) <- get self, data