Routines
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9143: Find Hit Position
Used by the routines at UpdateEnemies and CheckObjectHitByShot.
Works out the screen position of the object that was hit, and sets up the hit data used by CheckShotCollisions. Does nothing if the collision flag at A1D8 is clear.
FindHitPosition 9143 LD IY,($AD46) Fetch the address of the object from CurrentObject.
9147 LD L,(IY+$11) Fetch its screen position into HL.
914A LD H,(IY+$12)
914D LD A,($5C29) Fetch the value from 5C29 into E.
9150 LD E,A
9151 LD A,($A1D8) Fetch the collision flag from A1D8 into D.
9154 LD D,A
9155 LD A,D Copy it into A.
9156 DEC A Subtract one.
9157 RET M Return if it was zero.
9158 LD A,($A2FA) Fetch the flag from SpriteVariables_RightEdge.
915B AND A Test it.
915C LD A,L Fetch the horizontal screen position.
915D JR Z,FindHitPosition_Clear Jump to FindHitPosition_Clear if the flag is clear.
915F ADD A,E Add the value from E.
9160 LD L,$08 Set the horizontal screen position to 08.
9162 SUB L Subtract it.
9163 LD E,A Keep the result in E.
9164 JR FindHitPosition_Store Jump to FindHitPosition_Store.
FindHitPosition_Clear 9166 ADD A,$17 Add 17 to the horizontal screen position.
9168 ADD A,E Add the value from E.
9169 JR NC,FindHitPosition_Store Jump to FindHitPosition_Store if there is no carry.
916B LD A,$EE Otherwise use EE...
916D SUB L ...less the horizontal screen position.
916E LD E,A Keep the result in E.
FindHitPosition_Store 916F LD ($ABA4),HL Store the position in CollisionBox.
9172 LD ($ABA6),DE Store the size in ABA6.
9176 LD A,H Fetch the vertical screen position.
9177 SUB D Subtract the collision flag.
9178 LD ($5C1E),A Store the result in ScratchPair.
917B RET Return.
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