Sherlock: Routine at F490

F490: Drawing Fill

Used by the routine at Drawing. Flood-fills from the pen and stores the ink at F60B.
DrawingFill	F490	LD ($F60B),A	Store the ink, save the pen and the picture pointer, and push the B0 end marker.
	F493	PUSH DE
	F494	PUSH HL
	F495	LD HL,$00B0
	F498	PUSH HL	Save the end marker and read the pixel under the pen.
DrawingFill_0	F499	CALL KeepOnlyBitsThatAreSet	Save the end marker and read the pixel under the pen.
	F49C	JR NZ,DrawingFill_Next	Go to DrawingFill_Next if the pixel under the pen is already set.
	F49E	CALL StepPenLeft	Step the pen left and try that pixel again until the left edge.
	F4A1	JR NZ,DrawingFill_0
	F4A3	JR DrawingFill_RecordDrawingPen	No set pixel to the left, so start filling from DrawingFill_RecordDrawingPen.
Plot this pixel and step the pen right.
DrawingFill_Next	F4A5	CALL PlotPixel	Plot this pixel, then step the pen right.
	F4A8	CALL StepPenRight	Plot this pixel, then step the pen right.
DrawingFill_RecordDrawingPen	F4AB	LD HL,$0000	Clear the two bytes that remember a seed.
	F4AE	LD ($F48E),HL	Clear the two bytes that remember a seed.
DrawingFill_Loop	F4B1	CALL StepPenUp	Go to DrawingFill_DrawingPenStep if the pen is already at the top edge.
	F4B4	LD A,$00
	F4B6	JR Z,DrawingFill_DrawingPenStep
	F4B8	CALL KeepOnlyBitsThatAreSet	Jump ahead to DrawingFill_StepPen if the pixel under the pen is already set.
	F4BB	LD A,$00
	F4BD	JR NZ,DrawingFill_StepPen
	F4BF	LD A,($F48E)	Jump to DrawingFill_StepPen if a seed is already saved for this row.
	F4C2	AND A
	F4C3	JR NZ,DrawingFill_StepPen
	F4C5	PUSH DE	Save this spot as a seed and note it in A.
	F4C6	LD A,$01	Save this spot as a seed and note it in A.
DrawingFill_StepPen	F4C8	PUSH AF	Save that note, step the pen down.
	F4C9	CALL StepPenDown	Save that note, step the pen down.
	F4CC	POP AF	Restore the note from the stack.
DrawingFill_DrawingPenStep	F4CD	LD ($F48E),A	Store the note and step the pen down.
	F4D0	CALL StepPenDown	Store the note and step the pen down.
	F4D3	LD A,$00	Go to DrawingFill_DrawingPenDrawing, with A=00 if the pen could not step down.
	F4D5	JR Z,DrawingFill_DrawingPenDrawing
	F4D7	CALL KeepOnlyBitsThatAreSet	Jump ahead to DrawingFill_StepPenUp if the pixel under the pen is already set.
	F4DA	LD A,$00
	F4DC	JR NZ,DrawingFill_StepPenUp
	F4DE	LD A,($F48F)	Jump to DrawingFill_StepPenUp if a seed is already saved for this row.
	F4E1	AND A
	F4E2	JR NZ,DrawingFill_StepPenUp
	F4E4	PUSH DE	Save this spot as a seed and note it in A.
	F4E5	LD A,$01	Save this spot as a seed and note it in A.
DrawingFill_StepPenUp	F4E7	PUSH AF	Save the note, step the pen up.
	F4E8	CALL StepPenUp	Save the note, step the pen up.
	F4EB	POP AF	Restore the note from the stack.
DrawingFill_DrawingPenDrawing	F4EC	LD ($F48F),A	Store the note in the other pen byte and plot this pixel.
	F4EF	CALL PlotPixel	Store the note in the other pen byte and plot this pixel.
	F4F2	CALL StepPenRight	Go to DrawingFill_ByteMatchesMarker if the pen is already at the right edge.
	F4F5	JR Z,DrawingFill_ByteMatchesMarker
	F4F7	CALL KeepOnlyBitsThatAreSet	Jump back to DrawingFill_Loop if the pixel under the pen is clear.
	F4FA	JR Z,DrawingFill_Loop
	F4FC	CALL PlotPixel	Plot this pixel.
DrawingFill_ByteMatchesMarker	F4FF	POP DE	Take the next seed off the stack, and go back to DrawingFill_0 until the B0 end marker, pushed at the start of the fill, comes off.
	F500	LD A,E
	F501	CP $B0
	F503	JR NZ,DrawingFill_0
	F505	LD A,$00	Clear the drawing ink.
	F507	LD ($F60B),A	Clear the drawing ink.
	F50A	POP HL	Restore the picture pointer and the pen from the stack.
	F50B	POP DE	Restore the picture pointer and the pen from the stack.
	F50C	RET	Return.