Routines
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39773: Draw Graphic Rotated Right
The handler of DrawGraphic for a graphic that is turned a quarter turn clockwise. This is the same as DrawGraphic_Transposed, except that it starts from the last row and works up using SubtractWidthFromAddress.
DrawGraphic_RotatedRight 39773 POP BC Restore the attribute and graphic ID from the stack.
39774 CALL GetBlendInstruction Call GetBlendInstruction to get the instruction to mix the graphic with the screen.
39777 LD (39816),A Write it over the instruction at 39816.
39780 CALL GetGraphicDetails Call GetGraphicDetails to get the details of the graphic.
39783 LD A,B Fetch the width.
39784 EXX Switch to the shadow registers.
39785 LD B,A Keep the number of columns in B'.
39786 LD L,128 L'=128 (the mask for the first column).
39788 EXX Switch back to the main registers.
39789 CALL FindLastRow Call FindLastRow to move on to the last row.
DrawGraphic_RotatedRight_Row 39792 PUSH BC Stash the width and height on the stack.
39793 PUSH DE Stash the position in the graphic on the stack.
39794 PUSH HL Stash the screen address on the stack.
DrawGraphic_RotatedRight_Bit 39795 LD A,(DE) Fetch the byte of the graphic.
39796 EXX Switch to the shadow registers.
39797 AND L Mask the column.
39798 JR Z,DrawGraphic_RotatedRight_Shift Jump to DrawGraphic_RotatedRight_Shift if the bit is not set.
39800 SCF Set the carry flag.
DrawGraphic_RotatedRight_Shift 39801 RL H Shift the bit into H'.
39803 EXX Switch back to the main registers.
39804 CALL SubtractWidthFromAddress Call SubtractWidthFromAddress to move up to the previous row of the graphic.
39807 DEC C Decrease the height by one.
39808 LD A,C Fetch the number of rows left.
39809 AND %00000111 Keep only bits 0-2.
39811 JR NZ,DrawGraphic_RotatedRight_Bit Jump to DrawGraphic_RotatedRight_Bit until eight bits have been gathered.
39813 EXX Switch to the shadow registers.
39814 LD A,H Fetch the byte that was built from the column.
39815 EXX Switch back to the main registers.
39816 NOP This is replaced by an instruction that mixes A with the screen.
39817 LD (HL),A Write A to the screen.
39818 INC L Move HL on to the next byte.
39819 LD A,C Fetch the number of rows left.
39820 AND A Jump to DrawGraphic_RotatedRight_Bit if there are more bytes in this row of the screen.
39821 JR NZ,DrawGraphic_RotatedRight_Bit
39823 POP HL Restore the screen address from the stack.
39824 CALL ScreenPosition1PixelAbove Call ScreenPosition1PixelAbove to move up a line.
39827 POP DE Restore the position in the graphic from the stack.
39828 POP BC Restore the width and height from the stack.
39829 EXX Switch to the shadow registers.
39830 RRC L Move the mask on to the next column.
39832 EXX Switch back to the main registers.
39833 JR NC,DrawGraphic_RotatedRight_Row Jump to DrawGraphic_RotatedRight_Row if there are more columns in this byte.
39835 EXX Switch to the shadow registers.
39836 DEC B Decrease the number of columns by one.
39837 EXX Switch back to the main registers.
39838 RET Z Return if all of the columns have been drawn.
39839 INC DE Move DE on to the next byte.
39840 JR DrawGraphic_RotatedRight_Row Jump back to DrawGraphic_RotatedRight_Row to draw the next row of the graphic.
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