Routines
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B1F2: Clear Pixel Block
Used by the routines at StartRound, ClearMessageArea and ClearLargeWindow.
Clears a rectangle of the display file.
Input
HL Screen address of the top left byte
B Width in bytes
C Height in pixel rows
ClearPixelBlock B1F2 PUSH BC Save the dimensions.
B1F3 PUSH HL Save the screen address of the start of the row.
ClearPixelBlock_Byte B1F4 LD (HL),$00 Clear the current byte of the row.
B1F6 INC L Move on to the next byte.
B1F7 DJNZ ClearPixelBlock_Byte Loop back until the whole row has been cleared.
B1F9 POP HL Restore the screen address of the start of the row.
B1FA CALL ScreenPosition1PixelBelow Move down to the next pixel row using ScreenPosition1PixelBelow.
B1FD POP BC Restore the dimensions.
B1FE DEC C Decrease the pixel row counter by one.
B1FF JR NZ,ClearPixelBlock Loop back until every row has been cleared.
B201 RET Return.
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