shell: horline working now

And we give a high-level error when the pixel buffer fills up.

1 files changed, 9 insertions, 1 deletions

diff --git a/500fake-screen.mu b/500fake-screen.mu
index 7b2c3177..fce0dc5d 100644
--- a/500fake-screen.mu
+++ b/500fake-screen.mu
@@ -52,8 +52,10 @@ fn initialize-screen _screen: (addr screen), width: int, height: int {
     tmp <- multiply width
     populate data-addr, tmp
   }
-  # pixels
+  # allocate space for 16 pixels per 16x8 character. So one column of pixels
+  # per character.
   var pixels-ah/ecx: (addr handle stream pixel) <- get screen, pixels
+  tmp <- shift-left 4
   populate-stream pixels-ah, tmp
   # screen->cursor-x = 0
   dest <- get screen, cursor-x
@@ -105,6 +107,12 @@ fn pixel screen: (addr screen), x: int, y: int, color: int {
   var screen/eax: (addr screen) <- copy screen
   var dest-stream-ah/eax: (addr handle stream pixel) <- get screen, pixels
   var dest-stream/eax: (addr stream pixel) <- lookup *dest-stream-ah
+  {
+    var full?/eax: boolean <- stream-full? dest-stream
+    compare full?, 0/false
+    break-if-=
+    abort "tried to draw too many pixels on the fake screen; adjust initialize-screen"
+  }
   write-to-stream dest-stream, src
 }