Routines
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30379: Draw Actor Sprite Row
Does the same as DrawOldSpriteRow_Aligned, but for the sprite prepared by PrepareActorSprite.
Input
DE Address of the sprite data
HL Screen address
Output
DE Address of the next row of sprite data
HL Screen address of the row above
The entry point for a sprite which is aligned to a character cell.
DrawActorSpriteRow_Aligned 30379 EX DE,HL DE=the row of sprite data, and HL=the address of the next row.
30380 EX (SP),HL HL=the screen address, and the address of the next row of sprite data is stored on the stack.
30381 JR DrawSpriteRow_Write Jump to DrawSpriteRow_Write.
This entry point is used by the routine at XORSpriteLoop.
The entry point for a sprite which is not aligned to a character cell.
DrawActorSpriteRow 30383 PUSH HL Stash the screen address on the stack.
30384 EX DE,HL HL=the address of the sprite data, and DE=the screen address.
30385 PUSH DE Stash the screen address on the stack again.
30386 LD D,(HL) D=the first byte of the row.
30387 INC HL Move to the next byte of sprite data.
30388 LD E,(HL) E=the second byte of the row.
30389 INC HL Move on to the next row of sprite data.
30390 EX DE,HL HL=the row of sprite data, and DE=the address of the next row.
30391 XOR A A=0.
Self modifying code; the operand of this command is written by 30104. It jumps into the sequence of shifts below, so that the row is moved right by the right number of pixels.
DrawActorSpriteRow_Shift 30392 JR DrawActorSpriteRow_Shift Jump to the first shift to do.
Shift the row left by up to seven bits; the bits which are shifted out of the row end up in A. The fourth shift is done with a longer command, but the jumps still land on the start of a shift.
30394 ADD HL,HL Shift HL left by one, moving the bit shifted out into A.
30395 ADC A,A
Shift the row left by up to seven bits; the bits which are shifted out of the row end up in A. The fourth shift is done with a longer command, but the jumps still land on the start of a shift.
30396 ADD HL,HL Shift HL left by one, moving the bit shifted out into A.
30397 ADC A,A
Shift the row left by up to seven bits; the bits which are shifted out of the row end up in A. The fourth shift is done with a longer command, but the jumps still land on the start of a shift.
30398 ADD HL,HL Shift HL left by one, moving the bit shifted out into A.
30399 ADC A,A
30400 ADC HL,HL Shift HL left by one, moving the bit shifted out into A.
30402 ADC A,A
30403 ADD HL,HL Shift HL left by one, moving the bit shifted out into A.
30404 ADC A,A
30405 ADD HL,HL Shift HL left by one, moving the bit shifted out into A.
30406 ADC A,A
30407 ADD HL,HL Shift HL left by one, moving the bit shifted out into A.
30408 ADC A,A
30409 EX DE,HL DE=the shifted row, and HL=the address of the next row of sprite data.
30410 EX (SP),HL HL=the screen address, and the address of the next row of sprite data is stored on the stack.
30411 XOR (HL) Exclusive OR the first byte (in A) onto the screen.
30412 LD (HL),A Write the result to the screen.
30413 INC L Move to the next byte on the screen.
30414 JR DrawSpriteRow_Write Jump to DrawSpriteRow_Write.
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