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Routines |
| Prev: 857F | Up: Map | Next: 85D9 |
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XOR the old sprite (normal registers) and the new sprite (shadow registers) onto the screen one row at a time, using C as each sprite's row counter. Any rows left in SpriteCachedRows and SpriteRowsLeft are then picked up.
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Draw remaining rows from the current graphic pair.
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| XORSpriteLoop | 858E | LD A,C | Jump to XORSpriteLoop_TryShadow if the row counter is zero. | |||||||
| 858F | AND A | |||||||||
| 8590 | JR Z,XORSpriteLoop_TryShadow | |||||||||
| 8592 | DEC C | Decrease the row counter and XOR the next row of the old sprite. | ||||||||
| 8593 | CALL XORSpriteLoop_LoadPair | |||||||||
| 8596 | EXX | Switch to the shadow registers. | ||||||||
| 8597 | LD A,C | Jump to XORSpriteLoop_NextSide if the shadow row counter is zero. | ||||||||
| 8598 | AND A | |||||||||
| 8599 | JR Z,XORSpriteLoop_NextSide | |||||||||
| XORSpriteLoop_Loop | 859B | DEC C | Decrease the shadow row counter and XOR the next row of the new sprite. | |||||||
| 859C | CALL PrepareSpriteWrite | |||||||||
| XORSpriteLoop_NextSide | 859F | EXX | Switch back and loop to XORSpriteLoop. | |||||||
| 85A0 | JR XORSpriteLoop | |||||||||
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No more rows on this side; try the other register set.
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| XORSpriteLoop_TryShadow | 85A2 | EXX | Switch to the shadow registers. | |||||||
| 85A3 | LD A,C | Jump to XORSpriteLoop_Loop if the shadow row counter is still live. | ||||||||
| 85A4 | AND A | |||||||||
| 85A5 | JR NZ,XORSpriteLoop_Loop | |||||||||
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Finish the sprites if either has rows left to draw.
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| XORSpriteLoop_FinishSprite | 85A7 | EXX | Switch back to the normal registers. | |||||||
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This entry point is used by the routine at DrawSprite.
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| XORSpriteLoop_Write | 85A8 | LD A,($5E5A) | Return if both SpriteCachedRows and SpriteRowsLeft are zero. | |||||||
| 85AB | LD C,A | |||||||||
| 85AC | LD A,($5E59) | |||||||||
| 85AF | OR C | |||||||||
| 85B0 | RET Z | |||||||||
| 85B1 | XOR A | Write 00 to SpriteCachedRows and switch register sets. | ||||||||
| 85B2 | LD ($5E5A),A | |||||||||
| 85B5 | EXX | |||||||||
| 85B6 | LD A,($5E59) | Load the remaining row count and clear A. | ||||||||
| 85B9 | LD C,A | |||||||||
| 85BA | XOR A | |||||||||
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This entry point is used by the routine at DrawSprite.
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| XORSpriteLoop_NextPair | 85BB | LD ($5E59),A | Write the remaining row count to SpriteRowsLeft. | |||||||
| 85BE | EXX | Switch back and loop to XORSpriteLoop. | ||||||||
| 85BF | JR XORSpriteLoop | |||||||||
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Copy of XORSpritePairUp for the old sprite. The self-modified jump at XORSpriteLoop_Shift lands here when the sprite is byte-aligned.
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| 85C1 | EX DE,HL | XOR the graphic pair onto the screen and move up one pixel. | ||||||||
| 85C2 | EX (SP),HL | |||||||||
| 85C3 | LD A,D | |||||||||
| 85C4 | XOR (HL) | |||||||||
| 85C5 | LD (HL),A | |||||||||
| 85C6 | INC L | |||||||||
| 85C7 | LD A,E | |||||||||
| 85C8 | XOR (HL) | |||||||||
| 85C9 | LD (HL),A | |||||||||
| 85CA | POP DE | |||||||||
| 85CB | DEC L | |||||||||
| 85CC | JP ScreenPosition1PixelAbove | |||||||||
| XORSpriteLoop_LoadPair | 85CF | EX DE,HL | Load the next graphic pair from DE. | |||||||
| 85D0 | PUSH DE | |||||||||
| 85D1 | LD D,(HL) | |||||||||
| 85D2 | INC HL | |||||||||
| 85D3 | LD E,(HL) | |||||||||
| 85D4 | INC HL | |||||||||
| 85D5 | EX DE,HL | |||||||||
| 85D6 | XOR A | |||||||||
| XORSpriteLoop_Shift | 85D7 | JR XORSpriteLoop_Shift | Self-modifying shift. The operand is written by 866A. | |||||||
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