Routines
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62830: Drawing Line
Used by the routine at Drawing.
Draws a straight line from the pen. Bit 0 of the direction chooses a steep line.
DrawingLine 62830 BIT 0,C Jump ahead to DrawingLine_PlotPixel if bit 0 is set (steep line).
62832 JR NZ,DrawingLine_PlotPixel
62834 PUSH HL Keep the picture pointer and the counters, then plot this pixel.
62835 PUSH BC
DrawingLine_0 62836 CALL PlotPixel
62839 BIT 2,C Jump ahead to DrawingLine_Next if bit 2 is clear.
62841 JR Z,DrawingLine_Next
62843 CALL StepPenLeft Go to DrawingLine_BringSavedCount if the pen is already at the left edge.
62846 JR Z,DrawingLine_BringSavedCount
62848 JR DrawingLine_TestCountFinished The pen has moved left, so skip the rightward step and join DrawingLine_TestCountFinished.
Steps the pen right, and steps it up or down (bit 1) when this pixel column is finished.
DrawingLine_Next 62850 CALL StepPenRight Go to DrawingLine_BringSavedCount if the pen is already at the right edge.
62853 JR Z,DrawingLine_BringSavedCount
DrawingLine_TestCountFinished 62855 DEC B Jump ahead to DrawingLine_1 if the count is not finished.
62856 JR NZ,DrawingLine_1
62858 BIT 1,C Jump ahead to DrawingLine_StepPenUp if bit 1 is clear.
62860 JR Z,DrawingLine_StepPenUp
62862 CALL StepPenDown Go to DrawingLine_BringSavedCount if the pen is already at the bottom edge.
62865 JR Z,DrawingLine_BringSavedCount
62867 JR DrawingLine_CountHasRun Carry on with the line once this step is ready.
Steps the pen up and repeats for the pixels still left.
DrawingLine_StepPenUp 62869 CALL StepPenUp Go to DrawingLine_BringSavedCount if the pen is already at the top edge.
62872 JR Z,DrawingLine_BringSavedCount
DrawingLine_CountHasRun 62874 POP BC Restore the counters from the stack.
62875 PUSH BC Keep a copy, and plot the next pixel from DrawingLine_0 until the length in L runs out.
DrawingLine_1 62876 DEC L
62877 JR NZ,DrawingLine_0
DrawingLine_BringSavedCount 62879 POP BC Restore the saved count and the saved pointer from the stack.
62880 POP HL
62881 RET Return.
Plots this pixel and steps down when bit 1 is set.
DrawingLine_PlotPixel 62882 PUSH HL Keep the picture pointer and the counters, then plot this pixel.
62883 PUSH BC
DrawingLine_2 62884 CALL PlotPixel
62887 BIT 1,C Jump ahead to DrawingLine_StepPenUpAgain if bit 1 is clear.
62889 JR Z,DrawingLine_StepPenUpAgain
62891 CALL StepPenDown Go to DrawingLine_BringSavedCountAgain if the pen is already at the bottom edge.
62894 JR Z,DrawingLine_BringSavedCountAgain
62896 JR DrawingLine_TestCountFinishedAgain Skip the upward step and carry on from DrawingLine_TestCountFinishedAgain.
Steps the pen up, and steps it left or right when this pixel row is finished.
DrawingLine_StepPenUpAgain 62898 CALL StepPenUp Go to DrawingLine_BringSavedCountAgain if the pen is already at the top edge.
62901 JR Z,DrawingLine_BringSavedCountAgain
DrawingLine_TestCountFinishedAgain 62903 DEC B Jump ahead to DrawingLine_3 if the count is not finished.
62904 JR NZ,DrawingLine_3
62906 BIT 2,C Jump ahead to DrawingLine_StepsPenRight if bit 2 is clear.
62908 JR Z,DrawingLine_StepsPenRight
62910 CALL StepPenLeft Go to DrawingLine_BringSavedCountAgain if the pen is already at the left edge.
62913 JR Z,DrawingLine_BringSavedCountAgain
62915 JR DrawingLine_CountHasRunAgain Carry on with the line once the other step is ready.
Steps the pen right and repeats for the pixels still left.
DrawingLine_StepsPenRight 62917 CALL StepPenRight Go to DrawingLine_BringSavedCountAgain if the pen is already at the right edge.
62920 JR Z,DrawingLine_BringSavedCountAgain
DrawingLine_CountHasRunAgain 62922 POP BC Restore the counters from the stack.
62923 PUSH BC And plot the next pixel from DrawingLine_2 until the length in L runs out.
DrawingLine_3 62924 DEC L
62925 JR NZ,DrawingLine_2
DrawingLine_BringSavedCountAgain 62927 POP BC Restore the saved count and the saved pointer from the stack.
62928 POP HL
62929 RET Return.
View the equivalent code in;
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