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Routines |
| Prev: 915C | Up: Map | Next: 919E |
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Used by the routines at LocateTerrainCell and DrawTerrain.
Copy eight bytes of terrain graphic from TerrainUDGs into the screen column in DE.
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Copy eight bytes of terrain graphic into the screen column.
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| DrawTerrainColumn | 917C | PUSH HL | Stash the cell pointer and the screen address on the stack. | |||||||
| 917D | PUSH DE | |||||||||
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Work out the address of the graphic for the terrain cell.
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| 917E | LD L,(HL) | Fetch the terrain cell. | ||||||||
| 917F | LD H,$00 | H=00. | ||||||||
| 9181 | ADD HL,HL | Multiply the cell index by 08. | ||||||||
| 9182 | ADD HL,HL | |||||||||
| 9183 | ADD HL,HL | |||||||||
| 9184 | LD DE,$F66E | DE=TerrainUDGs. | ||||||||
| 9187 | ADD HL,DE | Point HL at that graphic. | ||||||||
| 9188 | LD B,$08 | Set a pixel row counter in B for 08 loops. | ||||||||
| 918A | POP DE | Restore the screen address from the stack, but stash a copy of it on the stack again. | ||||||||
| 918B | PUSH DE | |||||||||
| DrawTerrainColumn_Loop | 918C | LD A,(HL) | Copy the graphic byte to the screen. | |||||||
| 918D | LD (DE),A | |||||||||
| 918E | INC HL | Move onto the next graphic byte. | ||||||||
| 918F | INC D | Move down one pixel row. | ||||||||
| 9190 | DJNZ DrawTerrainColumn_Loop | Decrease the row counter by one and loop back to DrawTerrainColumn_Loop until the column is drawn. | ||||||||
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Advance to the next screen row and the next terrain cell.
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| 9192 | POP DE | Restore the screen column from the stack. | ||||||||
| 9193 | LD A,E | Advance the screen pointer by one character row. | ||||||||
| 9194 | ADD A,$20 | |||||||||
| 9196 | LD E,A | |||||||||
| 9197 | LD A,D | Add the carry into the high byte. | ||||||||
| 9198 | ADC A,$00 | |||||||||
| 919A | LD D,A | |||||||||
| 919B | POP HL | Restore the cell pointer from the stack. | ||||||||
| 919C | INC HL | Move onto the next cell. | ||||||||
| 919D | RET | Return. | ||||||||
| Prev: 915C | Up: Map | Next: 919E |