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Routines |
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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 | 34190 | LD A,C | Jump to XORSpriteLoop_TryShadow if the row counter is zero. | |||||||
| 34191 | AND A | |||||||||
| 34192 | JR Z,XORSpriteLoop_TryShadow | |||||||||
| 34194 | DEC C | Decrease the row counter and XOR the next row of the old sprite. | ||||||||
| 34195 | CALL XORSpriteLoop_LoadPair | |||||||||
| 34198 | EXX | Switch to the shadow registers. | ||||||||
| 34199 | LD A,C | Jump to XORSpriteLoop_NextSide if the shadow row counter is zero. | ||||||||
| 34200 | AND A | |||||||||
| 34201 | JR Z,XORSpriteLoop_NextSide | |||||||||
| XORSpriteLoop_Loop | 34203 | DEC C | Decrease the shadow row counter and XOR the next row of the new sprite. | |||||||
| 34204 | CALL PrepareSpriteWrite | |||||||||
| XORSpriteLoop_NextSide | 34207 | EXX | Switch back and loop to XORSpriteLoop. | |||||||
| 34208 | JR XORSpriteLoop | |||||||||
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No more rows on this side; try the other register set.
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| XORSpriteLoop_TryShadow | 34210 | EXX | Switch to the shadow registers. | |||||||
| 34211 | LD A,C | Jump to XORSpriteLoop_Loop if the shadow row counter is still live. | ||||||||
| 34212 | AND A | |||||||||
| 34213 | JR NZ,XORSpriteLoop_Loop | |||||||||
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Finish the sprites if either has rows left to draw.
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| XORSpriteLoop_FinishSprite | 34215 | 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 | 34216 | LD A,(24154) | Return if both SpriteCachedRows and SpriteRowsLeft are zero. | |||||||
| 34219 | LD C,A | |||||||||
| 34220 | LD A,(24153) | |||||||||
| 34223 | OR C | |||||||||
| 34224 | RET Z | |||||||||
| 34225 | XOR A | Write 0 to SpriteCachedRows and switch register sets. | ||||||||
| 34226 | LD (24154),A | |||||||||
| 34229 | EXX | |||||||||
| 34230 | LD A,(24153) | Load the remaining row count and clear A. | ||||||||
| 34233 | LD C,A | |||||||||
| 34234 | XOR A | |||||||||
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This entry point is used by the routine at DrawSprite.
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| XORSpriteLoop_NextPair | 34235 | LD (24153),A | Write the remaining row count to SpriteRowsLeft. | |||||||
| 34238 | EXX | Switch back and loop to XORSpriteLoop. | ||||||||
| 34239 | 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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| 34241 | EX DE,HL | XOR the graphic pair onto the screen and move up one pixel. | ||||||||
| 34242 | EX (SP),HL | |||||||||
| 34243 | LD A,D | |||||||||
| 34244 | XOR (HL) | |||||||||
| 34245 | LD (HL),A | |||||||||
| 34246 | INC L | |||||||||
| 34247 | LD A,E | |||||||||
| 34248 | XOR (HL) | |||||||||
| 34249 | LD (HL),A | |||||||||
| 34250 | POP DE | |||||||||
| 34251 | DEC L | |||||||||
| 34252 | JP ScreenPosition1PixelAbove | |||||||||
| XORSpriteLoop_LoadPair | 34255 | EX DE,HL | Load the next graphic pair from DE. | |||||||
| 34256 | PUSH DE | |||||||||
| 34257 | LD D,(HL) | |||||||||
| 34258 | INC HL | |||||||||
| 34259 | LD E,(HL) | |||||||||
| 34260 | INC HL | |||||||||
| 34261 | EX DE,HL | |||||||||
| 34262 | XOR A | |||||||||
| XORSpriteLoop_Shift | 34263 | JR XORSpriteLoop_Shift | Self-modifying shift. The operand is written by 34410. | |||||||
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