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Routines |
| Prev: BB3A | Up: Map | Next: BB9F |
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Used by the routine at DrawLevelObjects.
Draws each of the objects of a group of a cell, using DrawObject. The group is at IY and the cell is at CellPosition. The first byte of a group has the number of objects in bits 0-4, and if bit 4 of it is set there is an extra byte, as described for GroupTable. The next two bytes and the extra byte make up a row of flags that is shifted left by one bit after each object, so that each object has a flag of its own.
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| DrawGroupObjects | BB3C | LD HL,($5CB9) | Fetch the position of the cell. | |||||
| BB3F | LD A,L | Add the column of the cell to its row. | ||||||
| BB40 | ADD A,H | |||||||
| BB41 | LD ($BFA6),A | Patch it into BFA6 as the depth of the objects. | ||||||
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Work out where the view starts, relative to the cell, and patch it into the drawing code.
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| BB44 | LD HL,$8000 | HL is 8000. | ||||||
| BB47 | LD DE,($5CE7) | Fetch the vertical origin of the view. | ||||||
| BB4B | AND A | Clear the carry flag. | ||||||
| BB4C | SBC HL,DE | Take the origin away. | ||||||
| BB4E | LD ($BFBA),HL | Patch the result into BFBA. | ||||||
| BB51 | LD HL,$803F | HL is 803F. | ||||||
| BB54 | LD DE,($5CEE) | Fetch the horizontal origin of the view. | ||||||
| BB58 | AND A | Clear the carry flag. | ||||||
| BB59 | SBC HL,DE | Take the origin away. | ||||||
| BB5B | LD ($C061),HL | Patch the result into C061. | ||||||
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Read the header of the group.
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| BB5E | PUSH IY | Put the address of the group onto the stack... | ||||||
| BB60 | POP IX | ...and take it off into IX. | ||||||
| BB62 | LD A,(IX+$00) | Fetch the first byte of the group. | ||||||
| BB65 | AND %00011111 | Keep the number of objects. | ||||||
| BB67 | LD B,A | Keep it in B. | ||||||
| BB68 | LD H,(IX+$01) | Fetch the first byte of the flags. | ||||||
| BB6B | LD L,(IX+$02) | Fetch the second byte of the flags. | ||||||
| BB6E | INC IX | Move past the first byte of the group... | ||||||
| BB70 | INC IX | ...and the first byte of the flags. | ||||||
| BB72 | AND %00010000 | Test whether the group has an extra byte of flags. | ||||||
| DrawGroupObjects_Header | BB74 | JR Z,DrawGroupObjects_Objects | Jump to DrawGroupObjects_Objects if there is no extra byte, with A as zero. | |||||
| BB76 | LD A,(IX+$01) | Fetch the extra byte of flags. | ||||||
| BB79 | INC IX | Move past the extra byte. | ||||||
| DrawGroupObjects_Objects | BB7B | LD ($BB8E),HL | Patch the flags into the instructions that load them after each object... | |||||
| BB7E | LD ($BB8C),A | ...including the extra byte. | ||||||
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Draw each object, and then move the row of flags along by one.
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| DrawGroupObjects_Loop | BB81 | INC IX | Move onto the first byte of the object. | |||||
| BB83 | PUSH BC | Save the number of objects left. | ||||||
| BB84 | CALL DrawObject | Draw the object. | ||||||
| BB87 | INC IX | Move past the second byte of the object... | ||||||
| BB89 | INC IX | ...and the third. | ||||||
| BB8B | LD A,$00 | Fetch the extra byte of flags, which is patched in. | ||||||
| BB8D | LD HL,$0000 | Fetch the other two bytes of flags, which are patched in. | ||||||
| BB90 | RLA | Shift the extra byte left... | ||||||
| BB91 | RL L | ...then the second byte... | ||||||
| BB93 | RL H | ...and then the first byte. | ||||||
| BB95 | LD ($BB8C),A | Patch the extra byte back in. | ||||||
| BB98 | LD ($BB8E),HL | Patch the other two bytes back in. | ||||||
| BB9B | POP BC | Restore the number of objects left. | ||||||
| BB9C | DJNZ DrawGroupObjects_Loop | Decrease the number of objects and loop back to DrawGroupObjects_Loop until all of them have been drawn. | ||||||
| BB9E | RET | Return. | ||||||
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