Routines
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C5A9: Test Overlap In X
Used by the routines at TestObjectIntersections, TestNearObject, BlockMovementInX, BlockMovementInY and BlockMovementInZ.
Tests whether two objects overlap along x, once the first has moved by its new speed along x. They overlap when the distance between the x positions is smaller than the two widths added together.
Input
C New speed along x of the first object
IX The address of the first object
IY The address of the second object
Output
F Carry flag set if the objects overlap
Compare the x distance with the widths.
TestOverlapInX C5A9 LD A,(IX+$04) Fetch the width of the first object.
C5AC ADD A,(IY+$04) Add the width of the second object.
C5AF LD D,A Copy the total to D.
C5B0 LD A,(IX+$01) Fetch the x position of the first object.
C5B3 ADD A,C Add C.
C5B4 SUB (IY+$01) Subtract the x position of the second object.
C5B7 JP P,TestOverlapInX_Compare Jump to TestOverlapInX_Compare if the sign flag is clear.
C5BA NEG Negate A.
TestOverlapInX_Compare C5BC SUB D Subtract D.
C5BD RET Return.
View the equivalent code in;
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