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Routines |
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Handler for the object type 136 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 8 pixels apart, and the rows are 24 pixels apart: the y positions of the rows are 48 72 96 and 120 and the x positions of the first rocks are 120 122 126 and 130. 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 70 (yellow).
An object touches the formation according to Check_Rock_Formation_Contact.
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| Handle_Rock_Formation | 60718 | BIT 0,(IX+15) | Jump to Handle_Rock_Formation_Colour to colour the formation if it has been drawn already. | |||||
| 60722 | JR Z,Handle_Rock_Formation_Colour | |||||||
| 60724 | LD (IX+1),120 | Set the x position of the first rock to 120. | ||||||
| 60728 | LD (IX+3),48 | Set the y position of the first row to 48. | ||||||
| 60732 | LD C,4 | Set the number of rocks in the first row (and of rows) to four. | ||||||
| 60734 | LD (IX+5),70 | Set the attribute of the rocks to 70 (yellow). | ||||||
| Handle_Rock_Formation_Row | 60738 | LD B,C | Set the number of rocks in the row. | |||||
| Handle_Rock_Formation_Rock | 60739 | PUSH BC | Stash the counters. | |||||
| 60740 | CALL Update_Object_Sprite | Draw the rock. | ||||||
| 60743 | SET 0,(IX+15) | Set bit 0 of the redraw flags, so that the next rock does not erase the last one. | ||||||
| 60747 | LD A,(IX+1) | Fetch the x position. | ||||||
| 60750 | ADD A,8 | Move on to the next rock. | ||||||
| 60752 | LD (IX+1),A | Set the x position. | ||||||
| 60755 | POP BC | Restore the counters. | ||||||
| 60756 | DJNZ Handle_Rock_Formation_Rock | Loop back until the row has been drawn. | ||||||
| 60758 | LD A,C | Fetch the number of rows left. | ||||||
| 60759 | SLA A | Double it. | ||||||
| 60761 | DEC A | Subtract one. | ||||||
| 60762 | SLA A | Double it again. | ||||||
| 60764 | NEG | Negate it. | ||||||
| 60766 | ADD A,136 | Add 136 to make the x position of the first rock of the next row. | ||||||
| 60768 | LD (IX+1),A | Set the x position. | ||||||
| 60771 | LD A,(IX+3) | Fetch the y position. | ||||||
| 60774 | ADD A,24 | Move on to the next row. | ||||||
| 60776 | LD (IX+3),A | Set the y position. | ||||||
| 60779 | DEC C | Jump back to Handle_Rock_Formation_Row until all the rows have been drawn. | ||||||
| 60780 | JR NZ,Handle_Rock_Formation_Row | |||||||
| 60782 | RES 0,(IX+15) | Reset bit 0 of the redraw flags. | ||||||
| 60786 | RET | Return. | ||||||
| Handle_Rock_Formation_Colour | 60787 | LD HL,12408 | Set the x position 120 in L and the y position 48 in H. | |||||
| 60790 | CALL AttributeAddress | Get the attribute address of the cell. | ||||||
| 60793 | LD DE,27 | Set the offset to the start of the next row (the row is 32 cells long and five have been set). | ||||||
| 60796 | LD C,10 | Set the number of rows to colour to ten. | ||||||
| Handle_Rock_Formation_Colour_Row | 60798 | LD B,5 | Set the number of cells in each row to five. | |||||
| Handle_Rock_Formation_Colour_Cell | 60800 | LD (HL),70 | Set the attribute of the cell to 70 (yellow). | |||||
| 60802 | INC L | Move on to the next cell. | ||||||
| 60803 | DJNZ Handle_Rock_Formation_Colour_Cell | Loop back until the row has been coloured. | ||||||
| 60805 | ADD HL,DE | Move on to the next row. | ||||||
| 60806 | DEC C | Jump back to Handle_Rock_Formation_Colour_Row until all the rows have been coloured. | ||||||
| 60807 | JR NZ,Handle_Rock_Formation_Colour_Row | |||||||
| 60809 | RET | Return. | ||||||
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