|
Routines |
| Prev: 653E | Up: Map | Next: 6588 |
|
Used by the routines at HandlerExplosion and HandlerPlayer.
Shows the player's position on the map in the sidebar as a pixel which flashes on and off every 08 frames. When the marker moves, the screen byte it was covering is put back, using the copy saved in PlayerMarker_Byte. The address of that byte is held in PlayerMarker_Address.
|
||||||||
| FlashPlayerMarker | 6557 | CALL LocatePlayerMarker | Work out the pixel co-ordinates of the marker using LocatePlayerMarker. | |||||
|
Has the marker moved? The saved value is a screen address, whereas HL holds pixel co-ordinates, so these are only equal by coincidence.
|
||||||||
| 655A | PUSH HL | Stash the pixel co-ordinates on the stack. | ||||||
| 655B | LD DE,($5E36) | Fetch the screen address saved for the marker (PlayerMarker_Address). | ||||||
| 655F | AND A | Reset the carry flag. | ||||||
| 6560 | SBC HL,DE | Compare the pixel co-ordinates with the saved screen address. | ||||||
| 6562 | POP HL | Restore the pixel co-ordinates from the stack. | ||||||
| 6563 | JR Z,FlashPlayerMarker_Flash | Jump to FlashPlayerMarker_Flash if the result was zero. | ||||||
|
Put back the screen byte that was covered by the marker.
|
||||||||
| 6565 | PUSH HL | Stash the pixel co-ordinates on the stack. | ||||||
| 6566 | LD HL,($5E36) | Fetch the screen address of the byte the marker covered (PlayerMarker_Address). | ||||||
| 6569 | LD A,($5E38) | Fetch the screen byte that the marker covered (PlayerMarker_Byte). | ||||||
| 656C | LD (HL),A | Put the screen byte back. | ||||||
| 656D | POP HL | Restore the pixel co-ordinates from the stack. | ||||||
|
This entry point is used by the routine at NewGame.
Save the screen byte at the position of the marker.
|
||||||||
| FlashPlayerMarker_SaveByte | 656E | PUSH HL | Stash the pixel co-ordinates on the stack. | |||||
| 656F | CALL ScreenAddress | Convert the pixel co-ordinates to a screen address using ScreenAddress. | ||||||
| 6572 | LD ($5E36),HL | Save the screen address of the marker at PlayerMarker_Address. | ||||||
| 6575 | LD A,(HL) | Fetch the screen byte at the marker. | ||||||
| 6576 | LD ($5E38),A | Save the screen byte at PlayerMarker_Byte. | ||||||
| 6579 | POP HL | Restore the pixel co-ordinates from the stack. | ||||||
|
Flash the marker, setting the pixel on one phase and clearing it on the other.
|
||||||||
| FlashPlayerMarker_Flash | 657A | LD BC,$0101 | Set the size of the marker, a single pixel (0101). | |||||
| 657D | LD A,($5E29) | Fetch the game timer from GameTimer. | ||||||
| 6580 | AND %00001000 | Keep only bit 3, which changes every 08 frames. | ||||||
| 6582 | JP NZ,SetPixels | If the bit is set then jump to SetPixels to draw the marker. | ||||||
| 6585 | JP ClearPixels | Else jump to ClearPixels to remove the marker. | ||||||
| Prev: 653E | Up: Map | Next: 6588 |
