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# Use the built-in font to draw a grapheme to real screen.
#
# We need to do this in machine code because Mu doesn't have global variables
# yet (for the start of video memory).
== code
draw-grapheme-on-real-screen: # g: grapheme, x: int, y: int, color: int
# . prologue
55/push-ebp
89/<- %ebp 4/r32/esp
# . save registers
50/push-eax
51/push-ecx
52/push-edx
53/push-ebx
56/push-esi
# var letter-bitmap/esi = font[g]
8b/-> *(ebp+8) 6/r32/esi
c1 4/subop/shift-left %esi 4/imm8
8d/copy-address *(esi+0x8800) 6/r32/esi # font-start
# if (letter-bitmap >= 0x9000) return # characters beyond ASCII currently not supported
81 7/subop/compare %esi 0x9000/imm32
7d/jump-if->= $draw-grapheme:end/disp8
# edx = y
8b/-> *(ebp+0x10) 2/r32/edx
# var ymax/ebx: int = y + 16
8b/-> *(ebp+0x10) 3/r32/ebx
81 0/subop/add %ebx 0x10/imm32
{
# if (y >= ymax) break
39/compare %edx 3/r32/ebx
7d/jump-if->= break/disp8
# eax = x + 7
8b/-> *(ebp+0xc) 0/r32/eax
81 0/subop/add %eax 7/imm32
# var xmin/ecx: int = x
8b/-> *(ebp+0xc) 1/r32/ecx
# var row-bitmap/ebx: int = *letter-bitmap
53/push-ebx
8b/-> *esi 3/r32/ebx
{
# if (x < xmin) break
39/compare %eax 1/r32/ecx
7c/jump-if-< break/disp8
# shift LSB from row-bitmap into carry flag (CF)
c1 5/subop/shift-right-logical %ebx 1/imm8
# if LSB, draw a pixel
{
73/jump-if-not-CF break/disp8
(pixel-on-real-screen %eax %edx *(ebp+0x14))
}
# --x
48/decrement-eax
#
eb/jump loop/disp8
}
# reclaim row-bitmap
5b/pop-to-ebx
# ++y
42/increment-edx
# next bitmap row
46/increment-esi
#
eb/jump loop/disp8
}
$draw-grapheme:end:
# . restore registers
5e/pop-to-esi
5b/pop-to-ebx
5a/pop-to-edx
59/pop-to-ecx
58/pop-to-eax
# . epilogue
89/<- %esp 5/r32/ebp
5d/pop-to-ebp
c3/return
cursor-position-on-real-screen: # -> _/eax: int, _/ecx: int
# . prologue
55/push-ebp
89/<- %ebp 4/r32/esp
# TODO: support fake screen; we currently assume 'screen' is always 0 (real)
8b/-> *Default-next-x 0/r32/eax
8b/-> *Default-next-y 1/r32/ecx
$cursor-position:end:
# . epilogue
89/<- %esp 5/r32/ebp
5d/pop-to-ebp
c3/return
set-cursor-position-on-real-screen: # x: int, y: int
# . prologue
55/push-ebp
89/<- %ebp 4/r32/esp
# . save registers
50/push-eax
# TODO: support fake screen; we currently assume 'screen' is always 0 (real)
8b/-> *(ebp+8) 0/r32/eax
89/<- *Default-next-x 0/r32/eax
8b/-> *(ebp+0xc) 0/r32/eax
89/<- *Default-next-y 0/r32/eax
$set-cursor-position:end:
# . restore registers
58/pop-to-eax
# . epilogue
89/<- %esp 5/r32/ebp
5d/pop-to-ebp
c3/return
== data
Default-next-x:
0/imm32
Default-next-y:
0/imm32
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