30097: Insert a pixel column into a graphic buffer
Used by the routine at 30042. Slides the current contents of a row of the graphic buffer (at 60160, 60416 or 60672) one pixel to the left, and places the new pixel column into the slot freed up on the right.
Input
A
Pixel column byte
DE
Graphic buffer address
Output
30097
PUSH DE
30098
EXX
30099
POP HL
HL'=graphic buffer address
30100
LD C,8
There are 8 pixels to insert into the column
30102
LD B,8
There are 8 bytes per row in the buffer
30104
RRCA
Push a pixel into the carry flag
30105
RL (HL)
Drag the pixel from the carry flag into the buffer, and slide all the other pixels in the row one to the left