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Routines |
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Used by the routine at EndSegment.
Draws the pixels that finish the edge of a flat segment when the horizontal offset is not a multiple of eight. Nothing is drawn unless the segment is flat, its shape code (see EndShape) is 19 or 147 and steps have been flagged. The four bytes come from EdgePatternsRight or EdgePatternsLeft, depending on the type, and are stored going up the screen at the address in SegmentScreenAddress, except that only 2 are stored when the segment is at the top or bottom of the area.
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| DrawEdgePixels | 55402 | LD A,(52791) | The vertical step. | |||||
| 55405 | AND A | Return if A is not zero. | ||||||
| 55406 | RET NZ | |||||||
| 55407 | LD A,(23604) | The segment end shape. | ||||||
| 55410 | AND %01111111 | Keep the bits of A that are set in 127. | ||||||
| 55412 | CP 19 | Return if A is not 19. | ||||||
| 55414 | RET NZ | |||||||
| 55415 | LD A,(23599) | The flagged steps. | ||||||
| 55418 | AND A | Return if A is zero. | ||||||
| 55419 | RET Z | |||||||
| 55420 | LD HL,55377 | The edge patterns right. | ||||||
| 55423 | LD A,(IX+3) | Read offset 3 of IX. | ||||||
| 55426 | AND A | Jump to DrawEdgePixels_Table if A is zero. | ||||||
| 55427 | JR Z,DrawEdgePixels_Table | |||||||
| 55429 | LD HL,55390 | The edge patterns left. | ||||||
| DrawEdgePixels_Table | 55432 | LD A,(52801) | The horizontal offset. | |||||
| 55435 | AND %00000111 | Keep the bits of A that are set in 7. | ||||||
| 55437 | RET Z | Return if the zero flag is set. | ||||||
| 55438 | DEC A | Step A back. | ||||||
| 55439 | DEC A | Step A back. | ||||||
| 55440 | ADD A,A | Double A. | ||||||
| 55441 | LD E,A | E=A. | ||||||
| 55442 | LD D,0 | Clear D. | ||||||
| 55444 | ADD HL,DE | HL gains DE. | ||||||
| 55445 | EX DE,HL | Swap DE and HL. | ||||||
| 55446 | LD A,(55389) | The edge flag. | ||||||
| 55449 | AND A | Is A zero? | ||||||
| 55450 | LD HL,(52809) | Fetch the word at SegmentScreenAddress into HL. | ||||||
| 55453 | JR Z,DrawEdgePixels_Address | Jump to DrawEdgePixels_Address if the zero flag is set. | ||||||
| 55455 | LD (IX+1),0 | Store 0 at offset 1 of IX. | ||||||
| 55459 | LD A,L | A=L. | ||||||
| 55460 | SUB 32 | Subtract 32 from A. | ||||||
| 55462 | LD L,A | L=A. | ||||||
| 55463 | INC L | Advance L. | ||||||
| 55464 | INC L | Advance L. | ||||||
| 55465 | INC L | Advance L. | ||||||
| DrawEdgePixels_Address | 55466 | INC L | Advance L. | |||||
| 55467 | INC L | Advance L. | ||||||
| 55468 | INC L | Advance L. | ||||||
| 55469 | LD A,L | A=L. | ||||||
| 55470 | AND %00011111 | Keep the bits of A that are set in 31. | ||||||
| 55472 | DEC A | Step A back. | ||||||
| 55473 | CP 28 | Return if A is 28 or more. | ||||||
| 55475 | RET NC | |||||||
| 55476 | LD B,4 | B=4. | ||||||
| 55478 | LD A,(23597) | The segment screen row. | ||||||
| 55481 | CP 185 | Jump to DrawEdgePixels_Rows if A is not 185. | ||||||
| 55483 | JR NZ,DrawEdgePixels_Rows | |||||||
| 55485 | INC DE | Advance DE. | ||||||
| 55486 | INC DE | Advance DE. | ||||||
| 55487 | LD H,87 | H=87. | ||||||
| 55489 | LD A,L | A=L. | ||||||
| 55490 | AND %00011111 | Keep the bits of A that are set in 31. | ||||||
| 55492 | OR %11000000 | Set the bits of A that are set in 192. | ||||||
| 55494 | LD L,A | L=A. | ||||||
| 55495 | LD B,2 | B=2. | ||||||
| 55497 | JR DrawEdgePixels_Draw | Jump to DrawEdgePixels_Draw. | ||||||
| DrawEdgePixels_Rows | 55499 | CP 25 | Jump to DrawEdgePixels_Draw if A is not 25. | |||||
| 55501 | JR NZ,DrawEdgePixels_Draw | |||||||
| 55503 | LD B,2 | B=2. | ||||||
| DrawEdgePixels_Draw | 55505 | LD A,(DE) | Read DE. | |||||
| 55506 | LD (HL),A | Write A where HL points. | ||||||
| 55507 | INC DE | Advance DE. | ||||||
| 55508 | CALL MoveUpARow | Call MoveUpARow. | ||||||
| 55511 | DJNZ DrawEdgePixels_Draw | Decrease B and jump to DrawEdgePixels_Draw until none remain. | ||||||
| 55513 | RET | Return. | ||||||
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