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Routines |
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Draws the columns of a sprite which is not shifted or flipped. There is a piece of code for each of up to five columns, and the code for the width of the sprite is where the jump at DrawLines_Jump starts. Each piece takes the mask and the pixels for one byte of the row from the sprite data on the stack, wipes the screen where the mask is and puts the pixels in. The buffer address is in BC.
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The first unit of the run, which is used by sprites of five bytes wide.
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| DrawAlignedColumns | B44F | POP DE | Fetch the mask byte into E and the pixel byte into D. | |
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Fetch the byte from the buffer.
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| B450 | LD A,(BC) | Clear the screen bits under the mask. | ||
| B451 | CPL | |||
| B452 | OR E | |||
| B453 | CPL | |||
| B454 | OR D | Set the pixel bits. | ||
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Write the byte to the buffer.
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| B455 | LD (BC),A | Store the byte and move on to the next. | ||
| B456 | INC BC | |||
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The second unit, which is used by sprites that are four bytes wide.
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| B457 | POP DE | Fetch the mask into E and the pixels into D. | ||
| B458 | LD A,(BC) | Clear the screen bits under the mask. | ||
| B459 | CPL | |||
| B45A | OR E | |||
| B45B | CPL | |||
| B45C | OR D | Add the pixels. | ||
| B45D | LD (BC),A | Store the byte and move on to the next. | ||
| B45E | INC BC | |||
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The third unit, which is used by sprites that are three bytes wide.
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| B45F | POP DE | Fetch the mask into E and the pixels into D. | ||
| B460 | LD A,(BC) | Clear the screen bits under the mask. | ||
| B461 | CPL | |||
| B462 | OR E | |||
| B463 | CPL | |||
| B464 | OR D | Add the pixels. | ||
| B465 | LD (BC),A | Store the byte and move on to the next. | ||
| B466 | INC BC | |||
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The fourth unit, which is used by sprites that are two bytes wide.
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| B467 | POP DE | Fetch the mask into E and the pixels into D. | ||
| B468 | LD A,(BC) | Clear the screen bits under the mask. | ||
| B469 | CPL | |||
| B46A | OR E | |||
| B46B | CPL | |||
| B46C | OR D | Add the pixels. | ||
| B46D | LD (BC),A | Store the byte and move on to the next. | ||
| B46E | INC BC | |||
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The last unit, which is used by sprites that are one byte wide.
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| B46F | POP DE | Fetch the mask into E and the pixels into D. | ||
| B470 | LD A,(BC) | Clear the screen bits under the mask. | ||
| B471 | CPL | |||
| B472 | OR E | |||
| B473 | CPL | |||
| B474 | OR D | Add the pixels. | ||
| B475 | LD (BC),A | Store the byte. | ||
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Finish the row.
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| B476 | JP DrawLines_FinishRow | Jump to DrawLines_FinishRow to finish the row. | ||
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View the equivalent code in;
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| Prev: B3D3 | Up: Map | Next: B479 |