Cyberun: Routine at 42844

42844: Draw Shifted Row In Buffer

Draws one row of a sprite that is not aligned to a byte into the buffer used by DrawSprites, using the shift table that B points to. Each byte of the sprite makes two bytes in the buffer. The entry point depends on the width of the sprite in bytes, from five bytes at DrawShiftedRowInBuffer to one byte at 42892.

Input
B	High byte of the shift table
DE	Address of the data of the sprite
HL	Address in the buffer

DrawShiftedRowInBuffer

42844

LD A,(DE)

Fetch a byte of the sprite.

42845

LD C,A

Use it to look up the left part in the shift table.

42846

LD A,(BC)

Fetch the left part.

42847

OR (HL)

Set the pixels of the buffer.

42848

LD (HL),A

Store the byte.

42849

INC B

Move to the table of right parts.

42850

INC L

Move on to the next byte of the buffer.

42851

LD A,(BC)

Fetch the right part.

42852

OR (HL)

Set the pixels of the buffer.

42853

LD (HL),A

Store the byte.

42854

DEC B

Move back to the table of left parts.

42855

INC DE

Move on to the next byte of the sprite.

42856

LD A,(DE)

Fetch a byte of the sprite.

42857

LD C,A

Use it to look up the left part in the shift table.

42858

LD A,(BC)

Fetch the left part.

42859

OR (HL)

Set the pixels of the buffer.

42860

LD (HL),A

Store the byte.

42861

INC B

Move to the table of right parts.

42862

INC L

Move on to the next byte of the buffer.

42863

LD A,(BC)

Fetch the right part.

42864

OR (HL)

Set the pixels of the buffer.

42865

LD (HL),A

Store the byte.

42866

DEC B

Move back to the table of left parts.

42867

INC DE

Move on to the next byte of the sprite.

42868

LD A,(DE)

Fetch a byte of the sprite.

42869

LD C,A

Use it to look up the left part in the shift table.

42870

LD A,(BC)

Fetch the left part.

42871

OR (HL)

Set the pixels of the buffer.

42872

LD (HL),A

Store the byte.

42873

INC B

Move to the table of right parts.

42874

INC L

Move on to the next byte of the buffer.

42875

LD A,(BC)

Fetch the right part.

42876

OR (HL)

Set the pixels of the buffer.

42877

LD (HL),A

Store the byte.

42878

DEC B

Move back to the table of left parts.

42879

INC DE

Move on to the next byte of the sprite.

42880

LD A,(DE)

Fetch a byte of the sprite.

42881

LD C,A

Use it to look up the left part in the shift table.

42882

LD A,(BC)

Fetch the left part.

42883

OR (HL)

Set the pixels of the buffer.

42884

LD (HL),A

Store the byte.

42885

INC B

Move to the table of right parts.

42886

INC L

Move on to the next byte of the buffer.

42887

LD A,(BC)

Fetch the right part.

42888

OR (HL)

Set the pixels of the buffer.

42889

LD (HL),A

Store the byte.

42890

DEC B

Move back to the table of left parts.

42891

INC DE

Move on to the next byte of the sprite.

42892

LD A,(DE)

Fetch a byte of the sprite.

42893

LD C,A

Use it to look up the left part in the shift table.

42894

LD A,(BC)

Fetch the left part.

42895

OR (HL)

Set the pixels of the buffer.

42896

LD (HL),A

Store the byte.

42897

INC B

Move to the table of right parts.

42898

INC L

Move on to the next byte of the buffer.

42899

LD A,(BC)

Fetch the right part.

42900

OR (HL)

Set the pixels of the buffer.

42901

LD (HL),A

Store the byte.

42902

DEC B

Move back to the table of left parts.

42903

INC DE

Move on to the next byte of the sprite.

42904

LD A,0

Fetch the amount to skip, which was set at 42120.

42906

ADD A,L

Add it to the address in the buffer.

42907

LD L,A

Store it in L.

42908

EX AF,AF'

Switch to the count of rows.

42909

DEC A

Take one off.

42910

JP Z,DrawSprites_Dissolve

Jump to DrawSprites_Dissolve to finish when there are none left.

42913

EX AF,AF'

Switch back.

42914

JP (IX)

Draw the next row.