| Routines

28803: Check whether a character is on a roof with edges on each side

Used by the routine at 60812. Returns to the caller of that routine with A holding 1 (go right), 2 (go left) or 3 (go up) if the character is on the roof of the police station or the apartment building next to no. 19 and is heading for the edge of that roof. Otherwise returns with the zero flag set if the character is standing outside the entrance to a shop or other building.
Input
A | Identifier for the character's current location (see 60726)
H | Character number (215-230)
L | 12
28803 | CP 252 | Is the character on the roof of the apartment building next to no. 19?
28805 | JR Z,28811 | Jump if so
28807 | CP 108 | Is the character on the roof of the police station?
28809 | JR NZ,28816 | Jump if not
28811 | INC A | A=109 (police station) or 253 (apartment building next to no. 19)
28812 | CP (HL) | Is the character's destination on the edge of the roof of either the police station or the apartment building next to no. 19?
28813 | JR Z,28821 | Jump if so
28815 | DEC A | A=108 or 252
28816 | AND 15 | Keep only bits 0-3 of the location identifier
28818 | CP 2 | Set the zero flag if the character is standing outside the entrance to a shop or other building
28820 | RET |
The character is on the roof of the apartment building next to no. 19 or on the roof of the police station, and his destination is on the edge of that roof.
28821 | POP BC | Drop the return address from the stack
28822 | LD L,10 | Point HL at byte 10 of the character's buffer
28824 | LD A,(HL) | A=character's destination x-coordinate
28825 | LD L,1 | Compare this with the character's current x-coordinate
28827 | CP (HL)
28828 | DEC HL | Point HL at byte 0 of the character's buffer
28829 | BIT 7,(HL) | Set the zero flag if the character is facing left
28831 | LD A,3 | A=3 (go up)
28833 | JR C,28838 | Jump if the character is to the right of his destination
28835 | RET NZ | Return to the caller of 60812 with A=3 (go up) if the character is to the left of his destination and facing right
28836 | LD A,1 | A=1 (go right)
28838 | RET Z | Return to the caller of 60812 with A=1 (go right) if the character is to the left of his destination and facing left, or with A=3 (go up) if the character is to the right of his destination and facing left
28839 | DEC A | Return to the caller of 60812 with A=2 (go left) if the character is to the right of his destination and facing right
28840 | RET