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Routines |
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Used by the routines at order_unconstrained, candidate_already_first, iy_becomes_candidate and coincide_done.
IY is each other undrawn object in turn. If the end of the list is reached nothing has to be drawn before the candidate, and it is drawn by render_obj_no1.
C collects the comparison. On the Z axis (base +$03, height +$06): 0 if the candidate's base is at or above IY's top, 2 if IY's base is at or above the candidate's top, otherwise 1.
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| compare_next_obj | CEDB | LD A,(DE) | end of the list: nothing is behind the candidate | |||||||
| CEDC | INC DE | |||||||||
| CEDD | CP $FF | |||||||||
| CEDF | JP Z,render_obj_no1 | |||||||||
| CEE2 | BIT 7,A | already drawn: skip | ||||||||
| CEE4 | JR NZ,compare_next_obj | |||||||||
| CEE6 | CALL get_ptr_object | IY = this object; $5BCF points just past its entry | ||||||||
| CEE9 | LD ($5BCF),DE | |||||||||
| CEED | PUSH HL | |||||||||
| CEEE | POP IY | |||||||||
| CEF0 | PUSH IX | |||||||||
| CEF2 | POP BC | |||||||||
| CEF3 | AND A | the candidate itself: skip | ||||||||
| CEF4 | SBC HL,BC | |||||||||
| CEF6 | JR Z,compare_next_obj | |||||||||
| CEF8 | LD C,$00 | L = IY's top | ||||||||
| CEFA | LD A,(IY+$03) | |||||||||
| CEFD | ADD A,(IY+$06) | |||||||||
| CF00 | LD L,A | candidate's base at or above IY's top: Z code 0 | ||||||||
| CF01 | LD A,(IX+$03) | |||||||||
| CF04 | SUB L | |||||||||
| CF05 | JR NC,compare_along_y | |||||||||
| CF07 | LD A,(IX+$03) | L = the candidate's top | ||||||||
| CF0A | ADD A,(IX+$06) | |||||||||
| CF0D | LD L,A | |||||||||
| CF0E | LD A,(IY+$03) | IY's base at or above it: Z code 2 | ||||||||
| CF11 | SUB L | |||||||||
| CF12 | JR C,z_code_overlap | |||||||||
| CF14 | INC C | |||||||||
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