Routines
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C991: Fill Attributes
Used by the routines at DrawMenuOption, DamageShip, UpdateBeams, SetObjectAttributes, DrawShot, DrawSideFlames, DrawHUD, ColourFuelGauge, DrawFrame, ColourShip and ColourPlayfield.
Fills an area of the attributes with one value. The area starts with its width, its height and the attribute. The position is that of the bottom row of the area, and the rows are filled going up the screen.
Input
DE Address of the area
HL Position (H is the pixel row and L is the pixel column)
FillAttributes C991 LD A,(DE) Read DE.
C992 LD B,A B=A.
C993 INC DE Advance DE.
C994 LD A,(DE) Read DE.
C995 LD C,A C=A.
C996 CALL AttributeAddress Call AttributeAddress.
C999 INC DE Advance DE.
C99A LD A,(DE) Read DE.
C99B INC DE Advance DE.
C99C PUSH DE Stash DE on the stack.
C99D LD D,A D=A.
C99E LD E,B E=B.
FillAttributes_Row C99F PUSH HL Stash HL on the stack.
C9A0 LD B,E B=E.
FillAttributes_Loop C9A1 LD (HL),D Write D where HL points.
C9A2 INC HL Advance HL.
C9A3 DJNZ FillAttributes_Loop Decrease B and jump to FillAttributes_Loop until none remain.
C9A5 POP HL Bring HL back off the stack.
C9A6 PUSH BC Stash BC on the stack.
C9A7 LD BC,$0020 BC=20.
C9AA AND A Is A zero?
C9AB SBC HL,BC Subtract BC and the carry from HL.
C9AD POP BC Bring BC back off the stack.
C9AE DEC C Step C back.
C9AF JR NZ,FillAttributes_Row Jump to FillAttributes_Row if the zero flag is clear.
C9B1 POP DE Bring DE back off the stack.
C9B2 RET Return.
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