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Routines |
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This ANDs a tile in the mask buffer against the specified mask tile.
Used by the routine at render_mask_buffer.
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| mask_against_tile | BADC | PUSH HL | Save tile pointer | |||||||
| BADD | EXX | Switch register banks during the routine | ||||||||
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Point HL at mask_tiles[A]
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| BADE | LD L,A | Move the mask tile index into HL | ||||||||
| BADF | LD H,$00 | |||||||||
| BAE1 | ADD HL,HL | Multiply it by 8 | ||||||||
| BAE2 | ADD HL,HL | |||||||||
| BAE3 | ADD HL,HL | |||||||||
| BAE4 | LD BC,$8218 | Add base of mask_tiles array | ||||||||
| BAE7 | ADD HL,BC | |||||||||
| BAE8 | POP DE | Retrieve tile pointer | ||||||||
| BAE9 | LD B,$08 | Set B for 8 iterations | ||||||||
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Start loop
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| mat_loop | BAEB | LD A,(DE) | Fetch a byte of mask buffer | |||||||
| BAEC | AND (HL) | Mask it against a byte of mask tile | ||||||||
| BAED | LD (DE),A | Overwrite the input byte with result | ||||||||
| BAEE | INC L | Advance the mask tile pointer by a row | ||||||||
| BAEF | INC E | Advance the mask buffer pointer by a row | ||||||||
| BAF0 | INC E | |||||||||
| BAF1 | INC E | |||||||||
| BAF2 | INC E | |||||||||
| BAF3 | DJNZ mat_loop | ...loop | ||||||||
| BAF5 | EXX | Switch register banks back | ||||||||
| BAF6 | RET | Return | ||||||||
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