|
Routines |
| Prev: 42544 | Up: Map | Next: 42707 |
|
Used by the routine at DrawDirectionGauge.
Draws the ball at the tip of the needle of a direction gauge into the buffer at 62743 using self-modifying versions of the sprite drawing code at DrawShiftedRows. The ball is drawn from six pairs of mask and picture values at NeedleTipShapes (or the shifted version at 42719), which are taken from the stack. The value of DrawingPosition selects the version by bit 0, and the table of shifts to use by bits 1-2.
|
||||||||
| DrawNeedleTip | 42642 | LD (23770),SP | Save the stack pointer. | |||||
| 42646 | LD A,(23772) | Fetch the position of the tip of the needle from DrawingPosition. | ||||||
| 42649 | LD SP,42707 | Point the stack at the shape of the ball. | ||||||
| 42652 | BIT 0,A | Jump to DrawNeedleTip_Shift if bit 0 of the position is reset. | ||||||
| 42654 | JR Z,DrawNeedleTip_Shift | |||||||
| 42656 | LD SP,42719 | Point the stack at the shifted shape of the ball. | ||||||
| DrawNeedleTip_Shift | 42659 | AND %00000110 | Use bits 1-2, the shift in pixels. | |||||
| 42661 | JR Z,DrawNeedleTip_Unshifted | Jump to DrawNeedleTip_Unshifted if the ball is not to be shifted. | ||||||
| 42663 | EX DE,HL | Exchange DE and HL, so that DE is the address in the buffer. | ||||||
| 42664 | ADD A,248 | Add 248 to make the high byte of the address of the shift table. | ||||||
| 42666 | LD H,A | Set the high byte of HL to select the shift table. | ||||||
| 42667 | LD A,8 | Set the number of bytes to step back to the next row to 8... | ||||||
| 42669 | LD (46384),A | ...in the operand of the instruction at 46383. | ||||||
| 42672 | LD A,6 | Set the counter of rows to 6... | ||||||
| 42674 | EX AF,AF' | ...and store it in the alternate A. | ||||||
| 42675 | LD BC,46360 | Set BC to the address of the code at 46360. | ||||||
| 42678 | LD (46388),BC | Patch the jump at 46387 to go there. | ||||||
| 42682 | LD (46393),BC | Patch the jump at 46392 to go there. | ||||||
| 42686 | LD A,(DE) | Fetch the byte of the buffer. | ||||||
| 42687 | JP DrawShiftedRows_One | Jump to 46360 to draw the ball. | ||||||
| DrawNeedleTip_Unshifted | 42690 | LD A,249 | Set the low byte of the operand of the instruction at 46299 to 249... | |||||
| 42692 | LD (46300),A | ...to make the offset to the next row 65529. | ||||||
| 42695 | LD B,6 | Set the counter of rows to 6. | ||||||
| 42697 | LD DE,46293 | Point DE at the code at 46293. | ||||||
| 42700 | LD (46305),DE | Patch the jump at 46304 to go there. | ||||||
| 42704 | JP DrawUnshiftedRows_One | Jump to 46293 to draw the ball. | ||||||
| Prev: 42544 | Up: Map | Next: 42707 |