Routines
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CF38: Colour Segment
Used by the routine at FinishSegment.
Colours the attribute cells that a segment covers, one step at a time. Nothing is coloured if ScrollInFlag is set or if the drawing record has no screen address or no length. The number of cells across at each step (one to three) chooses the routine that paints the cells of a column: a flat segment is painted three cells across. The colour is TopTileColour for a tile on the top row and BottomTileColour for one on the bottom row, with the colours at SkyAttribute and UndergroundAttribute used for some of the tiles on map rows 0B and 0C.
Input
IX Address of the drawing record at ScrollWorld_Record
ColourSegment CF38 LD A,($5C3C) The scroll-in flag.
CF3B AND A Return if A is not zero.
CF3C RET NZ
CF3D LD A,(IX+$01) Read offset 01 of IX.
CF40 AND A Return if A is zero.
CF41 RET Z
CF42 LD A,(IX+$02) Read offset 02 of IX.
CF45 AND A Return if A is zero.
CF46 RET Z
CF47 LD A,($CE59) The horizontal step copy.
CF4A AND A Jump to ColourSegment_Cells if A is not zero.
CF4B JR NZ,ColourSegment_Cells
CF4D LD ($CE36),A Update the column step.
CF50 INC A Advance A.
CF51 LD ($5C24),A Update the column step size.
ColourSegment_Cells CF54 LD A,($5C24) The column step size.
CF57 INC A Advance A.
CF58 LD C,A C=A.
CF59 LD A,($E41B) The slope direction.
CF5C CP $FF Jump to ColourSegment_Painter if A is FF.
CF5E JR Z,ColourSegment_Painter
CF60 LD A,(IX+$00) Read offset 00 of IX.
CF63 SUB $02 Subtract 02 from A.
CF65 AND %11111000 Keep the bits of A that are set in F8.
CF67 LD (IX+$00),A Write A to offset 00 of IX.
ColourSegment_Painter CF6A LD A,C A=C.
CF6B LD IY,$D04F The paint one column.
CF6F CP $01 Jump to ColourSegment_Rows if A is 01.
CF71 JR Z,ColourSegment_Rows
CF73 LD IY,$D063 The paint two columns.
CF77 CP $02 Jump to ColourSegment_Rows if A is 02.
CF79 JR Z,ColourSegment_Rows
CF7B LD IY,$D082 The paint three columns.
ColourSegment_Rows CF7F LD A,($CE37) The vertical step.
CF82 SRL A Shift A right.
CF84 SRL A Shift A right.
CF86 SRL A Shift A right.
CF88 LD ($CE5A),A Update the vertical step copy.
CF8B LD L,(IX+$00) Read offset 00 of IX into L.
CF8E LD H,(IX+$01) Read offset 01 of IX into H.
CF91 LD A,($CE5A) The vertical step copy.
CF94 LD ($CE3E),A Update the attribute rows.
CF97 LD A,H A=H.
CF98 AND %00000111 Keep the bits of A that are set in 07.
CF9A XOR %00000111 Flip the bits of A that are set in 07.
CF9C JR Z,ColourSegment_Flat Jump to ColourSegment_Flat if the zero flag is set.
CF9E LD A,($CE3E) The attribute rows.
CFA1 INC A Advance A.
CFA2 LD ($CE3E),A Update the attribute rows.
ColourSegment_Flat CFA5 LD A,(IX+$03) Read offset 03 of IX.
CFA8 AND A Jump to ColourSegment_FlatCells if A is zero.
CFA9 JR Z,ColourSegment_FlatCells
CFAB CP $07 Jump to ColourSegment_Address if A is not 07.
CFAD JR NZ,ColourSegment_Address
ColourSegment_FlatCells CFAF LD IY,$D082 The paint three columns.
CFB3 XOR A Clear A.
CFB4 LD ($CE5A),A Update the vertical step copy.
CFB7 LD A,H A=H.
CFB8 SUB $0B Subtract 0B from A.
CFBA LD B,A B=A.
CFBB LD A,H A=H.
CFBC OR %00000111 Set the bits of A that are set in 07.
CFBE SUB B Subtract B from A.
CFBF SRL A Shift A right.
CFC1 SRL A Shift A right.
CFC3 SRL A Shift A right.
CFC5 LD ($CE3E),A Update the attribute rows.
ColourSegment_Address CFC8 LD B,L B=L.
CFC9 LD A,L A=L.
CFCA CP $F0 Jump to ColourSegment_Convert if A is less than F0.
CFCC JR C,ColourSegment_Convert
CFCE LD L,$00 Clear L.
ColourSegment_Convert CFD0 CALL AttributeAddress Call AttributeAddress.
CFD3 LD A,B A=B.
CFD4 CP $F0 Jump to ColourSegment_Colour if A is less than F0.
CFD6 JR C,ColourSegment_Colour
CFD8 DEC HL Step HL back.
ColourSegment_Colour CFD9 LD A,($5C3A) The top-tile colour.
CFDC LD C,A C=A.
CFDD LD A,($5C1D) The tile number.
CFE0 BIT 0,A Jump to ColourSegment_Row if bit 0 of A is clear.
CFE2 JR Z,ColourSegment_Row
CFE4 LD A,($5C3B) The bottom-tile colour.
CFE7 LD C,A C=A.
ColourSegment_Row CFE8 LD A,($CE58) The map row.
CFEB CP $0B Jump to ColourSegment_Special if A is 0B.
CFED JR Z,ColourSegment_Special
CFEF CP $0C Jump to ColourSegment_Paint if A is not 0C.
CFF1 JR NZ,ColourSegment_Paint
CFF3 LD A,($5C1D) The tile number.
CFF6 BIT 0,A Jump to ColourSegment_Paint if bit 0 of A is set.
CFF8 JR NZ,ColourSegment_Paint
CFFA JR ColourSegment_Alternate Jump to ColourSegment_Alternate.
ColourSegment_Special CFFC LD A,($5C1D) The tile number.
CFFF BIT 0,A Jump to ColourSegment_Paint if bit 0 of A is clear.
D001 JR Z,ColourSegment_Paint
ColourSegment_Alternate D003 LD A,($DC96) The underground attribute.
D006 LD C,A C=A.
D007 LD A,($CE3C) The vertical edge in the tile.
D00A CP $67 Jump to ColourSegment_Paint if A is 67 or more.
D00C JR NC,ColourSegment_Paint
D00E LD A,($DC95) The sky attribute.
D011 LD C,A C=A.
ColourSegment_Paint D012 LD DE,$0020 DE=20.
D015 LD B,(IX+$02) Read offset 02 of IX into B.
ColourSegment_Loop D018 PUSH BC Stash BC on the stack.
D019 LD A,($CE3E) The attribute rows.
D01C LD B,A B=A.
D01D PUSH HL Stash HL on the stack.
D01E CALL JumpToPainter Call JumpToPainter.
D021 POP HL Bring HL back off the stack.
D022 LD A,($CE5A) The vertical step copy.
D025 AND A Jump to ColourSegment_Across if A is zero.
D026 JR Z,ColourSegment_Across
D028 LD B,A B=A.
ColourSegment_Up D029 AND A Is A zero?
D02A SBC HL,DE Subtract DE and the carry from HL.
D02C DJNZ ColourSegment_Up Decrease B and jump to ColourSegment_Up until none remain.
ColourSegment_Across D02E LD A,($CE36) The column step.
D031 LD C,A C=A.
D032 LD B,$00 Clear B.
D034 BIT 7,A Jump to ColourSegment_Advance if bit 7 of A is clear.
D036 JR Z,ColourSegment_Advance
D038 DEC B Step B back.
ColourSegment_Advance D039 ADD HL,BC HL gains BC.
D03A POP BC Bring BC back off the stack.
D03B DJNZ ColourSegment_Loop Decrease B and jump to ColourSegment_Loop until none remain.
D03D LD A,($5C34) The segment end shape.
D040 AND %01111111 Keep the bits of A that are set in 7F.
D042 CP $13 Return if A is not 13.
D044 RET NZ
D045 LD A,($CE41) The horizontal offset.
D048 AND %00000111 Keep the bits of A that are set in 07.
D04A RET Z Return if the zero flag is set.
ColourSegment_Edge D04B LD A,($CE3E) The attribute rows.
D04E LD B,A B=A.
Continue on to PaintOneColumn.
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