Routines
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35121: Fill Attribute Row
Write D over a block of attributes, B columns wide and C rows high, stepping up a row at a time. Empty (zero) attributes are left alone.
Input
B Number of columns
C Number of rows
D Attribute value
HL Attribute address of the bottom-left cell
FillAttributeRow 35121 PUSH BC Stash the counters and attribute address.
35122 PUSH HL
FillAttributeRow_Loop 35123 LD A,(HL) Jump to FillAttributeRow_NextColumn if this attribute is empty.
35124 AND A
35125 JR Z,FillAttributeRow_NextColumn
35127 LD (HL),D Write the fill colour.
FillAttributeRow_NextColumn 35128 INC L Move onto the next column and loop back to FillAttributeRow_Loop.
35129 DJNZ FillAttributeRow_Loop
35131 POP HL Restore this row and step up one attribute row.
35132 LD BC,32
35135 AND A
35136 SBC HL,BC
35138 POP BC
35139 DEC C Decrease the height and loop back to FillAttributeRow until every row is painted.
35140 JR NZ,FillAttributeRow
35142 RET Return.
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