Routines
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47266: Test Overlap In X
Used by the routines at BlockMovementInX, BlockMovementInY, BlockMovementInZ, TestObjectIntersections and TestObjectCanBePickedUp.
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 47266 LD A,(IX+4) Fetch the width of the first object.
47269 ADD A,(IY+4) Add the width of the second object.
47272 LD D,A Copy the total to D.
Work out the distance between the centres, once the first has moved.
47273 LD A,(IX+1) Fetch the x position of the first object.
47276 ADD A,C Add C.
47277 SUB (IY+1) Subtract the x position of the second object.
47280 JP P,TestOverlapInX_Compare Jump to TestOverlapInX_Compare if the distance is positive.
47283 NEG Negate A.
TestOverlapInX_Compare 47285 SUB D Subtract D.
47286 RET Return.
View the equivalent code in;
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