Atic Atac: Routine at 40603

Used by the routines at DrawEntity, RemoveEntity and DisplayEntity.

XORs the old sprite and the new sprite onto the screen one row at a time, working up from the bottom row. The row counters are in C and C' (in the normal and the shadow register sets), and each register set holds the screen address in HL and the sprite data address in DE for one of the two sprites. When the counters run out, any rows left over in Old_Sprite_Row_Count and New_Sprite_Row_Count are drawn.

Drawing a sprite a second time erases it, so the old sprite is removed from where it was and the new sprite is drawn where it is now.

Used by the routines at DrawEntity, RemoveEntity and DisplayEntity. XORs the old sprite and the new sprite onto the screen one row at a time, working up from the bottom row. The row counters are in C and C' (in the normal and the shadow register sets), and each register set holds the screen address in HL and the sprite data address in DE for one of the two sprites. When the counters run out, any rows left over in Old_Sprite_Row_Count and New_Sprite_Row_Count are drawn. Drawing a sprite a second time erases it, so the old sprite is removed from where it was and the new sprite is drawn where it is now.
XORSpriteLoop	40603	LD A,C	Fetch the number of rows of the old sprite that are left.
	40604	AND A	Jump to XORSpriteLoop_Swap if there are no rows of the old sprite left to draw.
	40605	JR Z,XORSpriteLoop_Swap
	40607	DEC C	Decrease the row counter by one.
	40608	CALL DrawOldSpriteRow	Call DrawOldSpriteRow to draw the old sprite row.
	40611	EXX	Switch to the shadow registers.
	40612	LD A,C	Fetch the number of rows of the new sprite that are left.
	40613	AND A	Jump to XORSpriteLoop_Next if there are no rows of the new sprite left to draw.
	40614	JR Z,XORSpriteLoop_Next
XORSpriteLoop_Actor	40616	DEC C	Decrease the row counter by one.
	40617	CALL DrawActorSpriteRow	Call DrawActorSpriteRow to draw the new sprite row.
XORSpriteLoop_Next	40620	EXX	Switch to the normal registers.
	40621	JR XORSpriteLoop	Jump to XORSpriteLoop to draw the sprites onto the screen.
XORSpriteLoop_Swap	40623	EXX	Switch to the shadow registers.
	40624	LD A,C	Fetch the number of rows of the new sprite that are left.
	40625	AND A	Jump to XORSpriteLoop_Actor if there are more rows of the new sprite to draw.
	40626	JR NZ,XORSpriteLoop_Actor
This entry point is used by the routine at DisplayEntity.
XORSpriteLoop_Restore	40628	EXX	Switch to the normal registers.
This entry point is used by the routine at DisplayEntity. Fetch the number of rows left over from the old sprite and the new sprite. If there are none then the drawing is finished.
XORSpriteLoop_Remaining	40629	LD A,(24088)	Fetch the number of old sprite rows from Old_Sprite_Row_Count and keep it in C.
	40632	LD C,A
	40633	LD A,(24089)	Fetch the number of new sprite rows from New_Sprite_Row_Count.
	40636	OR C	Return if there are no rows left to draw.
	40637	RET Z	Return if there are no rows left to draw.
	40638	XOR A	A=0.
	40639	LD (24088),A	Update the number of old sprite rows in Old_Sprite_Row_Count.
	40642	EXX	Switch to the shadow registers.
	40643	LD A,(24089)	Fetch the number of new sprite rows from New_Sprite_Row_Count and keep it in C.
	40646	LD C,A
	40647	XOR A	A=0.
This entry point is used by the routine at DisplayEntity.
XORSpriteLoop_Continue	40648	LD (24089),A	Update the number of new sprite rows in New_Sprite_Row_Count.
	40651	EXX	Switch to the normal registers.
	40652	JR XORSpriteLoop	Jump to XORSpriteLoop to draw the sprites onto the screen.
View the equivalent code in; Cookie Sabre Wulf Underwurlde