6e36ce06dd
It's not really manageable to make the fake screen pixel-oriented. Feels excessive to compare things pixel by pixel when we will mostly be writing text to screen. It'll also make expected screen assertions more difficult to manage. So I'm not sure how to make assertions about pixels for now. Instead we'll introduce fake screens at draw-grapheme.
49 lines
1.4 KiB
Plaintext
49 lines
1.4 KiB
Plaintext
# check keyboard for a key
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# return 0 on no keypress or unrecognized key
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#
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# We need to do this in machine code because Mu doesn't have global variables
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# yet (for the keyboard buffer).
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== code
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read-key: # kbd: (addr keyboard) -> result/eax: byte
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# . prologue
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55/push-ebp
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89/<- %ebp 4/r32/esp
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# . save registers
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51/push-ecx
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# result = 0
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b8/copy-to-eax 0/imm32
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# ecx = keyboard
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8b/-> *(ebp+8) 1/r32/ecx
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81 7/subop/compare %ecx 0/imm32
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{
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75/jump-if-!= break/disp8
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# var read/ecx: byte = keyboard buffer's read index
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8b/-> *0x7dcc 1/r32/CL # keyboard-buffer-read
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# var next-key/eax: byte = *(keyboard buffer + ecx)
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8a/byte-> *(ecx+0x7dd0) 0/r32/AL # keyboard-buffer-data
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# if (next-key != 0) lock and remove from keyboard-buffer
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81 7/subop/compare %eax 0/imm32
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{
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74/jump-if-= break/disp8
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# TODO: add some instructions in this block to SubX if we ever want to
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# use bootstrap on baremetal programs
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fa/disable-interrupts
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c6 0/subop/copy-byte *(ecx+0x7dd0) 0/imm8
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ff 0/subop/increment *0x7dcc # keyboard-buffer-read
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81 4/subop/and *0x7dcc 0xf/imm32 # keyboard-buffer-read
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fb/enable-interrupts
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}
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# return
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eb $read-key:end/disp8
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}
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# TODO: fake keyboard
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$read-key:end:
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# . restore registers
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59/pop-to-ecx
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# . epilogue
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89/<- %esp 5/r32/ebp
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5d/pop-to-ebp
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c3/return
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