diff options
Diffstat (limited to 'baremetal/101screen.subx')
| -rw-r--r-- | baremetal/101screen.subx | 56 |
1 files changed, 25 insertions, 31 deletions
diff --git a/baremetal/101screen.subx b/baremetal/101screen.subx index 225efeec..5a26a86a 100644 --- a/baremetal/101screen.subx +++ b/baremetal/101screen.subx @@ -1,44 +1,38 @@ # 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: # screen: (addr screen), x: int, y: int, color: int +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 - # ecx = screen - 8b/-> *(ebp+8) 1/r32/ecx - 81 7/subop/compare %ecx 0/imm32 - { - 75/jump-if-!= break/disp8 - # bounds checks - 8b/-> *(ebp+0xc) 0/r32/eax - 3d/compare-eax-and 0/imm32 - 7c/jump-if-< $pixel:end/disp8 - 3d/compare-eax-and 0x400/imm32/1024 - 7d/jump-if->= $pixel:end/disp8 - 8b/-> *(ebp+0x10) 0/r32/eax - 3d/compare-eax-and 0/imm32 - 7c/jump-if-< $pixel:end/disp8 - 3d/compare-eax-and 0x300/imm32/768 - 7d/jump-if->= $pixel:end/disp8 - # eax = y*1024 + x - 8b/-> *(ebp+0x10) 0/r32/eax - c1/shift 4/subop/left %eax 0xa/imm8 - 03/add-> *(ebp+0xc) 0/r32/eax - # eax += location of frame buffer - 03/add-> *0x7f28 0/r32/eax - # *eax = color - 8b/-> *(ebp+0x14) 1/r32/ecx - 88/byte<- *eax 1/r32/CL - # return - eb $pixel:end/disp8 - } - # TODO: fake screen -$pixel:end: + # 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/imm32/1024 + 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/imm32/768 + 7d/jump-if->= $pixel-on-real-screen:end/disp8 + # eax = y*1024 + x + 8b/-> *(ebp+0xc) 0/r32/eax + c1/shift 4/subop/left %eax 0xa/imm8 + 03/add-> *(ebp+8) 0/r32/eax + # eax += location of frame buffer + 03/add-> *0x7f28 0/r32/eax # unsafe + # *eax = color + 8b/-> *(ebp+0x10) 1/r32/ecx + 88/byte<- *eax 1/r32/CL +$pixel-on-real-screen:end: # . restore registers 59/pop-to-ecx 58/pop-to-eax |