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Routines |
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Handler for the object type 88 the rock formation that hangs from the ceiling of the cave of a guardian (see Place_Rock_Formation).
The formation is made from ten of the rocks of the sprite at Sprite_Debris_1, in four rows of four, three, two and one rocks. They are drawn once, when bit 0 of the redraw flags is set. The rocks of a row are 08 pixels apart, and the rows are 18 pixels apart: the y positions of the rows are 30 48 60 and 78 and the x positions of the first rocks are 78 7A 7E and 82. The bit is set again before each rock is drawn so that nothing is erased.
After that the area that the formation covers is coloured on every call, with five cells in each of ten rows set to the attribute 46 (yellow).
An object touches the formation according to Check_Rock_Formation_Contact.
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| Handle_Rock_Formation | ED2E | BIT 0,(IX+$0F) | Jump to Handle_Rock_Formation_Colour to colour the formation if it has been drawn already. | |||||
| ED32 | JR Z,Handle_Rock_Formation_Colour | |||||||
| ED34 | LD (IX+$01),$78 | Set the x position of the first rock to 78. | ||||||
| ED38 | LD (IX+$03),$30 | Set the y position of the first row to 30. | ||||||
| ED3C | LD C,$04 | Set the number of rocks in the first row (and of rows) to four. | ||||||
| ED3E | LD (IX+$05),$46 | Set the attribute of the rocks to 46 (yellow). | ||||||
| Handle_Rock_Formation_Row | ED42 | LD B,C | Set the number of rocks in the row. | |||||
| Handle_Rock_Formation_Rock | ED43 | PUSH BC | Stash the counters. | |||||
| ED44 | CALL Update_Object_Sprite | Draw the rock. | ||||||
| ED47 | SET 0,(IX+$0F) | Set bit 0 of the redraw flags, so that the next rock does not erase the last one. | ||||||
| ED4B | LD A,(IX+$01) | Fetch the x position. | ||||||
| ED4E | ADD A,$08 | Move on to the next rock. | ||||||
| ED50 | LD (IX+$01),A | Set the x position. | ||||||
| ED53 | POP BC | Restore the counters. | ||||||
| ED54 | DJNZ Handle_Rock_Formation_Rock | Loop back until the row has been drawn. | ||||||
| ED56 | LD A,C | Fetch the number of rows left. | ||||||
| ED57 | SLA A | Double it. | ||||||
| ED59 | DEC A | Subtract one. | ||||||
| ED5A | SLA A | Double it again. | ||||||
| ED5C | NEG | Negate it. | ||||||
| ED5E | ADD A,$88 | Add 88 to make the x position of the first rock of the next row. | ||||||
| ED60 | LD (IX+$01),A | Set the x position. | ||||||
| ED63 | LD A,(IX+$03) | Fetch the y position. | ||||||
| ED66 | ADD A,$18 | Move on to the next row. | ||||||
| ED68 | LD (IX+$03),A | Set the y position. | ||||||
| ED6B | DEC C | Jump back to Handle_Rock_Formation_Row until all the rows have been drawn. | ||||||
| ED6C | JR NZ,Handle_Rock_Formation_Row | |||||||
| ED6E | RES 0,(IX+$0F) | Reset bit 0 of the redraw flags. | ||||||
| ED72 | RET | Return. | ||||||
| Handle_Rock_Formation_Colour | ED73 | LD HL,$3078 | Set the x position 78 in L and the y position 30 in H. | |||||
| ED76 | CALL AttributeAddress | Get the attribute address of the cell. | ||||||
| ED79 | LD DE,$001B | Set the offset to the start of the next row (the row is 20 cells long and five have been set). | ||||||
| ED7C | LD C,$0A | Set the number of rows to colour to ten. | ||||||
| Handle_Rock_Formation_Colour_Row | ED7E | LD B,$05 | Set the number of cells in each row to five. | |||||
| Handle_Rock_Formation_Colour_Cell | ED80 | LD (HL),$46 | Set the attribute of the cell to 46 (yellow). | |||||
| ED82 | INC L | Move on to the next cell. | ||||||
| ED83 | DJNZ Handle_Rock_Formation_Colour_Cell | Loop back until the row has been coloured. | ||||||
| ED85 | ADD HL,DE | Move on to the next row. | ||||||
| ED86 | DEC C | Jump back to Handle_Rock_Formation_Colour_Row until all the rows have been coloured. | ||||||
| ED87 | JR NZ,Handle_Rock_Formation_Colour_Row | |||||||
| ED89 | RET | Return. | ||||||
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