Cyberun: Routine at A75C

A75C: 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 A78C.

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

DrawShiftedRowInBuffer

A75C

LD A,(DE)

Fetch a byte of the sprite.

A75D

LD C,A

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

A75E

LD A,(BC)

Fetch the left part.

A75F

OR (HL)

Set the pixels of the buffer.

A760

LD (HL),A

Store the byte.

A761

INC B

Move to the table of right parts.

A762

INC L

Move on to the next byte of the buffer.

A763

LD A,(BC)

Fetch the right part.

A764

OR (HL)

Set the pixels of the buffer.

A765

LD (HL),A

Store the byte.

A766

DEC B

Move back to the table of left parts.

A767

INC DE

Move on to the next byte of the sprite.

A768

LD A,(DE)

Fetch a byte of the sprite.

A769

LD C,A

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

A76A

LD A,(BC)

Fetch the left part.

A76B

OR (HL)

Set the pixels of the buffer.

A76C

LD (HL),A

Store the byte.

A76D

INC B

Move to the table of right parts.

A76E

INC L

Move on to the next byte of the buffer.

A76F

LD A,(BC)

Fetch the right part.

A770

OR (HL)

Set the pixels of the buffer.

A771

LD (HL),A

Store the byte.

A772

DEC B

Move back to the table of left parts.

A773

INC DE

Move on to the next byte of the sprite.

A774

LD A,(DE)

Fetch a byte of the sprite.

A775

LD C,A

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

A776

LD A,(BC)

Fetch the left part.

A777

OR (HL)

Set the pixels of the buffer.

A778

LD (HL),A

Store the byte.

A779

INC B

Move to the table of right parts.

A77A

INC L

Move on to the next byte of the buffer.

A77B

LD A,(BC)

Fetch the right part.

A77C

OR (HL)

Set the pixels of the buffer.

A77D

LD (HL),A

Store the byte.

A77E

DEC B

Move back to the table of left parts.

A77F

INC DE

Move on to the next byte of the sprite.

A780

LD A,(DE)

Fetch a byte of the sprite.

A781

LD C,A

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

A782

LD A,(BC)

Fetch the left part.

A783

OR (HL)

Set the pixels of the buffer.

A784

LD (HL),A

Store the byte.

A785

INC B

Move to the table of right parts.

A786

INC L

Move on to the next byte of the buffer.

A787

LD A,(BC)

Fetch the right part.

A788

OR (HL)

Set the pixels of the buffer.

A789

LD (HL),A

Store the byte.

A78A

DEC B

Move back to the table of left parts.

A78B

INC DE

Move on to the next byte of the sprite.

A78C

LD A,(DE)

Fetch a byte of the sprite.

A78D

LD C,A

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

A78E

LD A,(BC)

Fetch the left part.

A78F

OR (HL)

Set the pixels of the buffer.

A790

LD (HL),A

Store the byte.

A791

INC B

Move to the table of right parts.

A792

INC L

Move on to the next byte of the buffer.

A793

LD A,(BC)

Fetch the right part.

A794

OR (HL)

Set the pixels of the buffer.

A795

LD (HL),A

Store the byte.

A796

DEC B

Move back to the table of left parts.

A797

INC DE

Move on to the next byte of the sprite.

A798

LD A,$00

Fetch the amount to skip, which was set at A488.

A79A

ADD A,L

Add it to the address in the buffer.

A79B

LD L,A

Store it in L.

A79C

EX AF,AF'

Switch to the count of rows.

A79D

DEC A

Take one off.

A79E

JP Z,DrawSprites_Dissolve

Jump to DrawSprites_Dissolve to finish when there are none left.

A7A1

EX AF,AF'

Switch back.

A7A2

JP (IX)

Draw the next row.