Avalon: Routine at 56439

56439: Draw/erase graphics - graphic tile out of bounds

Used by the routine at 56216.

Input
HL	Contains address of the vertical pixel offset in the graphic tile data

Gone 'out of bounds' on horizontal screen position so there's no need to draw this tile. Skip to the next one (checking if there are any left).

56439

INC HL

Move HL to the next address in the graphics data

56440

LD C,(HL)

This address contains the number of bytes in the tile graphic

56441

INC HL

Move HL to point to the start of the graphics data itself

Also jump in at to this point from the check at 56272, if out of bounds on vertical position (into bottom 3rd of screen)

HL	Pointing at address of first graphics byte in tile
C	Number of bytes in next tile graphic

56442

LD D,0

56444

LD E,C

DE now contains number of bytes left to draw in the current graphics tile

56445

ADD HL,DE

...Add to current graphics address pointer to skip over the rest of the tile graphics (as there's no need to draw them)

Decrement the tile counter and check to see if all tiles of the graphic have been drawn

56446

LD A,(60112)

Get tile counter (number of tiles in current graphic)

56449

DEC A

Decrement counter

56450

LD (60112),A

...and re-store

56453

JP NZ,56230

Still tiles to draw/erase? If so, go draw/erase them

56456

RET

All graphic tiles are now drawn/erased.