Routines
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34745: Write Sprite Row
Used by the routines at ClearSpriteScratch, DrawActorSprite and ContinueSpriteWrite.
XOR one graphic row from DE onto the screen at HL.
Input
HL Screen address
DE Graphic pointer
XOR one graphic row from DE onto the screen at HL.
WriteSpriteRow 34745 LD A,C Jump to ContinueSpriteWrite if the row counter is zero.
34746 AND A
34747 JR Z,ContinueSpriteWrite
34749 DEC C Decrease the row counter by one.
34750 PUSH BC Stash the counters and screen address.
34751 PUSH HL
WriteSpriteRow_Loop 34752 LD A,(DE) XOR the next graphic byte onto the screen.
34753 INC DE
34754 XOR (HL)
34755 LD (HL),A
34756 INC L Move to the next column and loop back to WriteSpriteRow_Loop.
34757 DJNZ WriteSpriteRow_Loop
Skip the unused graphic bytes, then step up one pixel line.
WriteSpriteRow_SkipRest 34759 JR WriteSpriteRow_SkipRest Self-modifying skip. The operand is written by 35064.
34761 INC DE Skip the remaining bytes of this graphic row.
34762 INC DE
34763 INC DE
34764 INC DE
34765 INC DE
34766 INC DE
34767 INC DE
34768 INC DE
34769 INC DE
34770 INC DE
34771 INC DE
34772 INC DE
34773 INC DE
34774 INC DE
34775 INC DE
34776 INC DE
34777 POP HL Restore the screen address from the stack.
34778 CALL ScreenPosition1PixelAbove Call ScreenPosition1PixelAbove.
34781 POP BC Restore the counters from the stack.
Switch to the other sprite and write its next row if it has rows left.
34782 EXX Jump to WriteSpriteRow_NextSide if the shadow row counter is zero.
34783 LD A,C
34784 AND A
34785 JR Z,WriteSpriteRow_NextSide
This entry point is used by the routine at ContinueSpriteWrite.
WriteSpriteRow_DecreaseShadow 34787 DEC C Decrease the shadow row counter.
34788 PUSH BC Stash the counters and the screen address on the stack.
34789 PUSH HL
WriteSpriteRow_XORByte 34790 LD A,(DE) XOR the next graphic byte onto the screen.
34791 INC DE
34792 XOR (HL)
34793 LD (HL),A
34794 INC L Move to the next column and loop back to WriteSpriteRow_XORByte.
34795 DJNZ WriteSpriteRow_XORByte
Skip the unused graphic bytes, then step up one pixel line.
WriteSpriteRow_SkipGraphic 34797 JR WriteSpriteRow_SkipGraphic Self-modifying skip. The operand is written by 34896 and ReadSpriteHeader_Loop.
34799 INC DE Skip the remaining bytes of this graphic row.
34800 INC DE
34801 INC DE
34802 INC DE
34803 INC DE
34804 INC DE
34805 INC DE
34806 INC DE
34807 INC DE
34808 INC DE
34809 INC DE
34810 INC DE
34811 INC DE
34812 INC DE
34813 INC DE
34814 INC DE
34815 POP HL Restore the screen address from the stack.
34816 CALL ScreenPosition1PixelAbove Call ScreenPosition1PixelAbove.
34819 POP BC Restore the counters from the stack.
WriteSpriteRow_NextSide 34820 EXX Switch back and loop to WriteSpriteRow.
34821 JR WriteSpriteRow
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