diff options
Diffstat (limited to '101screen.subx')
| -rw-r--r-- | 101screen.subx | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/101screen.subx b/101screen.subx new file mode 100644 index 00000000..46cee777 --- /dev/null +++ b/101screen.subx @@ -0,0 +1,42 @@ +# Primitives for screen control. +# +# We need to do this in machine code because Mu doesn't have global variables +# yet (for the start of video memory). + +== code + +pixel-on-real-screen: # x: int, y: int, color: int + # . prologue + 55/push-ebp + 89/<- %ebp 4/r32/esp + # . save registers + 50/push-eax + 51/push-ecx + # bounds checks + 8b/-> *(ebp+8) 0/r32/eax + 3d/compare-eax-and 0/imm32 + 7c/jump-if-< $pixel-on-real-screen:end/disp8 + 3d/compare-eax-and 0x400/imm32/screen-width=1024 + 7d/jump-if->= $pixel-on-real-screen:end/disp8 + 8b/-> *(ebp+0xc) 0/r32/eax + 3d/compare-eax-and 0/imm32 + 7c/jump-if-< $pixel-on-real-screen:end/disp8 + 3d/compare-eax-and 0x300/imm32/screen-height=768 + 7d/jump-if->= $pixel-on-real-screen:end/disp8 + # eax = y*1024 + x + 8b/-> *(ebp+0xc) 0/r32/eax + c1/shift 4/subop/left %eax 0xa/imm8 + 03/add-> *(ebp+8) 0/r32/eax + # eax += location of frame buffer + 03/add-> *0x8128 0/r32/eax # unsafe + # *eax = color + 8b/-> *(ebp+0x10) 1/r32/ecx + 88/byte<- *eax 1/r32/CL +$pixel-on-real-screen:end: + # . restore registers + 59/pop-to-ecx + 58/pop-to-eax + # . epilogue + 89/<- %esp 5/r32/ebp + 5d/pop-to-ebp + c3/return |