Routines
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ED9A: Handler: Ladders Descending
Used by the routines at PlayerControls_Kempston and PlayerControls.
Input
IX On entry will be set to TablePlayerAttributes
Handler_LaddersDescending ED9A LD A,(IX+$11) Jump to Handler_LaddersDescending_AlreadyOnLadder if *PlayerActionState is already on a ladder.
ED9D CP $03
ED9F JR Z,Handler_LaddersDescending_AlreadyOnLadder
EDA1 LD C,(IX+$00) C=*TablePlayerAttributes.
EDA4 LD B,(IX+$01) B=*PlayerVerticalCoordinate.
EDA7 LD HL,($5BD8) HL=*ReferenceLadders.
Handler_LaddersDescending_Loop EDAA LD A,(HL) Return if this ladder entry is the terminator (FF).
EDAB CP $FF
EDAD RET Z
EDAE INC HL Advance to the ladder vertical.
EDAF CP C Jump to Action_LadderDescend if this ladder is in the player's column.
EDB0 JR Z,Action_LadderDescend
EDB2 INC HL Advance to the next ladder entry.
EDB3 JR Handler_LaddersDescending_Loop Jump to Handler_LaddersDescending_Loop.
Action_LadderDescend EDB5 LD A,(HL) A=the ladder vertical.
EDB6 DEC A Move two rows up for the bottom bound.
EDB7 DEC A
EDB8 LD (IX+$13),A Write the lower ladder bound to *PlayerLadderBoundLower.
EDBB ADD A,$05 Add 05 for the top bound.
EDBD LD (IX+$12),A Write the upper ladder bound to *PlayerLadderBoundUpper.
EDC0 INC HL Advance to the next ladder entry.
EDC1 SUB B Compare that span with the player's vertical.
EDC2 CP $04 Jump to Handler_LaddersDescending_Loop if the player is not on this ladder.
EDC4 JR NC,Handler_LaddersDescending_Loop
EDC6 LD A,(IX+$11) Jump to AnimateDescending if *PlayerActionState is already on a ladder.
EDC9 CP $03
EDCB JR Z,AnimateDescending
Write the frame before the climb-down sprite we actually want (80) to *PlayerSpriteID. The next step adds 06 so the first drawn frame is correct.
EDCD LD (IX+$06),$7A Write 7A to *PlayerSpriteID.
EDD1 LD (IX+$11),$03 Set *PlayerActionState to on a ladder.
AnimateDescending EDD5 LD A,(IX+$06) Advance *PlayerSpriteID by one climb-down frame.
EDD8 ADD A,$06
EDDA LD (IX+$06),A
EDDD CP $98 Jump to SkipResetDescendingFrame if the climb-down frames have not wrapped (frame 98 begins the next animation).
EDDF JR NZ,SkipResetDescendingFrame
Reset the climbing-down player sprite to the first frame.
EDE1 LD (IX+$06),$80 Write 80 to *PlayerSpriteID.
SkipResetDescendingFrame EDE5 DEC (IX+$05) Set *PlayerVerticalMovement to move down.
EDE8 LD (IX+$02),$03 Centre *PlayerHorizontalPosition on the ladder.
EDEC RET Return.
Already climbing down; stop at the bottom bound.
Handler_LaddersDescending_AlreadyOnLadder EDED LD A,(IX+$01) Jump to AnimateDescending if *PlayerVerticalCoordinate has not reached *PlayerLadderBoundLower.
EDF0 CP (IX+$13)
EDF3 JR NZ,AnimateDescending
EDF5 RET Return.
This entry point is used by the routine at Handler_LaddersAscending.
Already climbing up; stop at the top bound.
Handler_LaddersAscending_AlreadyOnLadder EDF6 LD A,(IX+$12) Jump to AnimateAscending if *PlayerVerticalCoordinate has not reached *PlayerLadderBoundUpper.
EDF9 LD B,A
EDFA LD A,(IX+$01)
EDFD CP B
EDFE JR NZ,AnimateAscending
EE00 LD A,(IX+$03) Jump to AnimateAscending if *PlayerVerticalPosition is not 03.
EE03 CP $03
EE05 JR NZ,AnimateAscending
EE07 RET Return.
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