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Routines |
| Prev: 35409 | Up: Map | Next: 35560 |
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XOR the old (cached) image of a masked sprite off the screen and its new image on, row by row, using the remaining row counts in SpriteCachedRows (old image) and SpriteRowsLeft (new image).
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Draw remaining rows from the current masked pair.
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| MaskSprite | 35420 | LD A,C | Jump to MaskSprite_TryShadow if the row counter is zero. | |||||||
| 35421 | AND A | |||||||||
| 35422 | JR Z,MaskSprite_TryShadow | |||||||||
| 35424 | DEC C | Decrease the row counter and draw the next row of the old image. | ||||||||
| 35425 | CALL MaskSprite_LoadMask | |||||||||
| 35428 | EXX | Switch to the shadow registers. | ||||||||
| 35429 | LD A,C | Jump to MaskSprite_NextSide if the shadow row counter is zero. | ||||||||
| 35430 | AND A | |||||||||
| 35431 | JR Z,MaskSprite_NextSide | |||||||||
| MaskSprite_Loop | 35433 | DEC C | Decrease the shadow row counter and draw the next row of the new image. | |||||||
| 35434 | CALL MaskSprite_LoadMaskAgain | |||||||||
| MaskSprite_NextSide | 35437 | EXX | Switch back and loop to MaskSprite. | |||||||
| 35438 | JR MaskSprite | |||||||||
| MaskSprite_TryShadow | 35440 | EXX | Switch to the shadow registers. | |||||||
| 35441 | LD A,C | Jump to MaskSprite_Loop if the shadow row counter is still live. | ||||||||
| 35442 | AND A | |||||||||
| 35443 | JR NZ,MaskSprite_Loop | |||||||||
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Finish the sprite if any rows remain to be erased or drawn.
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| MaskSprite_FinishSprite | 35445 | EXX | Switch back to the normal registers. | |||||||
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This entry point is used by the routine at DrawObjectSprite.
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| MaskSprite_TestRemaining | 35446 | LD A,(24154) | Return if both SpriteCachedRows and SpriteRowsLeft are zero. | |||||||
| 35449 | LD C,A | |||||||||
| 35450 | LD A,(24153) | |||||||||
| 35453 | OR C | |||||||||
| 35454 | RET Z | |||||||||
| 35455 | XOR A | Write 0 to SpriteCachedRows and switch register sets. | ||||||||
| 35456 | LD (24154),A | |||||||||
| 35459 | EXX | |||||||||
| 35460 | LD A,(24153) | Load the remaining row count and clear A. | ||||||||
| 35463 | LD C,A | |||||||||
| 35464 | XOR A | |||||||||
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This entry point is used by the routine at DrawObjectSprite.
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| MaskSprite_StoreRowCount | 35465 | LD (24153),A | Write the remaining row count to SpriteRowsLeft. | |||||||
| 35468 | EXX | Switch back and loop to MaskSprite. | ||||||||
| 35469 | JR MaskSprite | |||||||||
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Reached by the self-modified shift (operand 242) when the mask is byte-aligned: only one screen byte is XORed.
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| 35471 | EX DE,HL | Switch the pair and jump to MaskSprite_XORSecond. | ||||||||
| 35472 | EX (SP),HL | |||||||||
| 35473 | JR MaskSprite_XORSecond | |||||||||
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Load and shift the next mask byte for a row of the old image.
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| MaskSprite_LoadMask | 35475 | PUSH HL | Load the next mask byte from DE. | |||||||
| 35476 | EX DE,HL | |||||||||
| 35477 | PUSH DE | |||||||||
| 35478 | LD D,0 | |||||||||
| 35480 | LD E,(HL) | |||||||||
| 35481 | INC HL | |||||||||
| 35482 | EX DE,HL | |||||||||
| MaskSprite_ShiftMask | 35483 | JR MaskSprite_ShiftMask | Self-modifying shift. The operand is written by 35678. | |||||||
| 35485 | ADD HL,HL | Shift the mask left into pixel alignment. | ||||||||
| 35486 | ADD HL,HL | |||||||||
| 35487 | ADD HL,HL | |||||||||
| 35488 | ADD HL,HL | |||||||||
| 35489 | ADD HL,HL | |||||||||
| 35490 | ADD HL,HL | |||||||||
| 35491 | ADD HL,HL | |||||||||
| 35492 | EX DE,HL | |||||||||
| MaskSprite_XORFirst | 35493 | EX (SP),HL | XOR the first mask byte onto the screen. | |||||||
| 35494 | LD A,D | |||||||||
| 35495 | XOR (HL) | |||||||||
| 35496 | LD (HL),A | |||||||||
| 35497 | INC L | |||||||||
| 35498 | LD A,L | Fetch the new column. | ||||||||
| 35499 | AND %00011111 | Keep only bits 0-4. | ||||||||
| 35501 | JR Z,MaskSprite_MoveUp | Jump to MaskSprite_MoveUp if the row wrapped. | ||||||||
| MaskSprite_XORSecond | 35503 | LD A,E | XOR the second mask byte onto the screen. | |||||||
| 35504 | XOR (HL) | |||||||||
| 35505 | LD (HL),A | |||||||||
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Step the screen address up one pixel line.
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| MaskSprite_MoveUp | 35506 | POP DE | Restore the graphic pointer and screen address. | |||||||
| 35507 | POP HL | |||||||||
| 35508 | DEC H | Move up one pixel. | ||||||||
| 35509 | LD A,H | |||||||||
| 35510 | CPL | |||||||||
| 35511 | AND %00000111 | Keep only bits 0-2. | ||||||||
| 35513 | RET NZ | Return if a character-row boundary was not crossed. | ||||||||
| 35514 | LD A,L | Subtract 32 from the column address. | ||||||||
| 35515 | SUB 32 | |||||||||
| 35517 | LD L,A | |||||||||
| 35518 | RET C | Return if that wrapped into the previous third. | ||||||||
| 35519 | LD A,H | Add 8 to the line byte. | ||||||||
| 35520 | ADD A,8 | |||||||||
| 35522 | LD H,A | |||||||||
| 35523 | RET | Return. | ||||||||
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Reached by the self-modified shift (operand 242) when the mask is byte-aligned: only one screen byte is XORed.
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| 35524 | EX DE,HL | Switch the pair and jump to MaskSprite_XORSecond. | ||||||||
| 35525 | EX (SP),HL | |||||||||
| 35526 | JR MaskSprite_XORSecond | |||||||||
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Load and shift the next mask byte for a row of the new image.
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| MaskSprite_LoadMaskAgain | 35528 | PUSH HL | Load the next mask byte from DE. | |||||||
| 35529 | EX DE,HL | |||||||||
| 35530 | PUSH DE | |||||||||
| 35531 | LD D,0 | |||||||||
| 35533 | LD E,(HL) | |||||||||
| 35534 | INC HL | |||||||||
| 35535 | EX DE,HL | |||||||||
| MaskSprite_ShiftAndPlace | 35536 | JR MaskSprite_ShiftAndPlace | Self-modifying shift. The operand is written by PositionMaskSprite_StoreShift. | |||||||
| 35538 | ADD HL,HL | Shift the mask left into pixel alignment and jump to MaskSprite_XORFirst. | ||||||||
| 35539 | ADD HL,HL | |||||||||
| 35540 | ADD HL,HL | |||||||||
| 35541 | ADD HL,HL | |||||||||
| 35542 | ADD HL,HL | |||||||||
| 35543 | ADD HL,HL | |||||||||
| 35544 | ADD HL,HL | |||||||||
| 35545 | EX DE,HL | |||||||||
| 35546 | JR MaskSprite_XORFirst | |||||||||
| 35548 | CALL PositionSprite | Call PositionSprite, clear SpriteCachedRows and jump to MaskSprite. | ||||||||
| 35551 | EXX | |||||||||
| 35552 | XOR A | |||||||||
| 35553 | LD (24154),A | |||||||||
| 35556 | LD C,A | |||||||||
| 35557 | JP MaskSprite | |||||||||
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