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make fake screens more realistic 

The real screen silently clips coordinates out of bounds.
This commit is contained in:
Kartik K. Agaram 2021-06-06 22:52:59 -07:00
parent b6e1cffd9b
commit b3869987da
1 changed files with 33 additions and 9 deletions
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42
500fake-screen.mu
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@ -18,8 +18,10 @@ type screen {
data: (handle array screen-cell)
cursor-x: int # [0..width)
cursor-y: int # [0..height)
invalid-cell-index: int
# pixel graphics
pixels: (handle array byte)
invalid-pixel-index: int
}
type screen-cell {
@ -45,7 +47,14 @@ fn initialize-screen _screen: (addr screen), width: int, height: int, pixel-grap
var data-ah/edi: (addr handle array screen-cell) <- get screen, data
var capacity/eax: int <- copy width
capacity <- multiply height
# add 1 for sentinel
capacity <- increment
#
populate data-ah, capacity
# save sentinel index
capacity <- decrement
var dest/ecx: (addr int) <- get screen, invalid-cell-index
copy-to *dest, capacity
}
# if necessary, populate screen->pixels
{
@ -56,7 +65,14 @@ fn initialize-screen _screen: (addr screen), width: int, height: int, pixel-grap
capacity <- shift-left 3/log2-font-width
capacity <- multiply height
capacity <- shift-left 4/log2-font-height
# add 1 for sentinel
capacity <- increment
#
populate pixels-ah, capacity
# save sentinel index
capacity <- decrement
var dest/ecx: (addr int) <- get screen, invalid-pixel-index
copy-to *dest, capacity
}
# screen->cursor-x = 0
dest <- get screen, cursor-x
@ -119,30 +135,34 @@ fn draw-code-point screen: (addr screen), c: code-point, x: int, y: int, color:
# fake screens only
fn screen-cell-index _screen: (addr screen), x: int, y: int -> _/ecx: int {
var screen/esi: (addr screen) <- copy _screen
# some bounds checks that aren't needed for a real screen, but might help catch problems
# if out of bounds, silently return a pixel that's never checked
{
compare x, 0
break-if->=
abort "screen-cell-index: negative x"
var invalid/eax: (addr int) <- get screen, invalid-cell-index
return *invalid
}
{
var xmax/eax: (addr int) <- get screen, width
var xcurr/ecx: int <- copy x
compare xcurr, *xmax
break-if-<
abort "screen-cell-index: x too high"
var invalid/eax: (addr int) <- get screen, invalid-cell-index
return *invalid
}
{
compare y, 0
break-if->=
abort "screen-cell-index: negative y"
var invalid/eax: (addr int) <- get screen, invalid-cell-index
return *invalid
}
{
var ymax/eax: (addr int) <- get screen, height
var ycurr/ecx: int <- copy y
compare ycurr, *ymax
break-if-<
abort "screen-cell-index: y too high"
var invalid/eax: (addr int) <- get screen, invalid-cell-index
return *invalid
}
var width-addr/eax: (addr int) <- get screen, width
var result/ecx: int <- copy y
@ -487,7 +507,8 @@ fn pixel-index _screen: (addr screen), x: int, y: int -> _/ecx: int {
{
compare x, 0
break-if->=
abort "screen-cell-index: negative x"
var invalid/eax: (addr int) <- get screen, invalid-pixel-index
return *invalid
}
{
var xmax-a/eax: (addr int) <- get screen, width
@ -495,12 +516,14 @@ fn pixel-index _screen: (addr screen), x: int, y: int -> _/ecx: int {
xmax <- shift-left 3/log2-font-width
compare x, xmax
break-if-<
abort "screen-cell-index: x too high"
var invalid/eax: (addr int) <- get screen, invalid-pixel-index
return *invalid
}
{
compare y, 0
break-if->=
abort "screen-cell-index: negative y"
var invalid/eax: (addr int) <- get screen, invalid-pixel-index
return *invalid
}
{
var ymax-a/eax: (addr int) <- get screen, height
@ -508,7 +531,8 @@ fn pixel-index _screen: (addr screen), x: int, y: int -> _/ecx: int {
ymax <- shift-left 4/log2-font-height
compare y, ymax
break-if-<
abort "screen-cell-index: y too high"
var invalid/eax: (addr int) <- get screen, invalid-pixel-index
return *invalid
}
var width-addr/eax: (addr int) <- get screen, width
var result/ecx: int <- copy y