Avalon: Routine at DD24

DD24: Draw the spell pointer arrow, spell charge icons and energy bar on the scroll

Used by the routines at E641, E6FA and E753.

Input
DE	Screen display address location to draw at

Draws the scroll arrow (called from E641), the spell 'charge' icons (called from E6FA) or the energy bar (called from E76E)

DD24

LD HL,($EB51)

Get graphics address pointer from 97C3

DD27

LD A,(HL)

Get the graphics address pointer low byte for the arrow (AFA6), the scroll charge icons (AEE7), or the energy bar (AEF3)

DD28

INC HL

High byte of the graphics address pointer

DD29

LD H,(HL)

DD2A

LD L,A

...HL register pair now contains the graphics address pointer for the relevant graphic

DD2B

LD C,(HL)

Number of tiles that make up the graphic

DD2C

INC HL

Move graphics address pointer along to start of first tile graphic

DD2D

INC HL

DD2E

INC HL

DD2F

LD B,(HL)

Number of bytes in the graphics tile to draw

DD30

INC HL

Move pointer to start of tile graphics

DD31

LD ($EADE),DE

Store screen display address position

Draw graphic tile on screen

DD35

LD A,(HL)

Copy graphic byte onto screen:

DD36

LD (DE),A

DD37

INC HL

Move to next graphic byte

DD38

LD A,D

Get pixel row

DD39

AND $07

DD3B

INC A

Move down to next pixel row

DD3C

CP $08

Are we crossing a pixel/character boundary?

DD3E

JR C,$DD50

...If not, move down 1 pixel row and continue drawing the graphic

DD40

LD A,D

...If so, recalculate screen display address. Get high byte of screen address

DD41

AND $F8

Reset the low 3 bits (pixel row number) to zero

DD43

LD D,A

DD44

LD A,E

Get the low byte of the screen address

DD45

ADD A,$20

Increment column by 32 to move down to next screen row

DD47

LD E,A

DD48

JR NC,$DD51

Crossing a 1/3 screen boundary? ...If not, skip next 3 instructions

DD4A

LD A,D

...If so, adjust high byte of screen address accordingly

DD4B

ADD A,$08

DD4D

LD D,A

Store correct screen address high byte back in D register

DD4E

JR $DD51

DD50

INC D

Move down 1 pixel row

DD51

DJNZ $DD35

Repeat for all pixel rows of this graphics tile

Continue to draw the remaining tiles in the graphic

DD53

LD DE,($EADE)

Retrieve screen display address

DD57

INC E

Move right one character square

DD58

DEC C

Decrement tile graphic counter

DD59

JR NZ,$DD2D

If there are tiles left in the graphic, draw the next one.

DD5B

RET