Routines
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25686: Draw Room Row
Used by the routine at Draw_Room_Rows_Loop.
Copies a single character row (8 pixel lines) from the room buffer to the screen buffer, then copies the corresponding colour attributes.
Input
HL Pointer to the room buffer row
Copy eight pixel lines from the room buffer to the screen buffer.
Draw_Room_Row 25686 LD B,8 Set the pixel line counter to 8 in B.
25688 PUSH HL Stash the room buffer pointer on the stack.
Draw_Room_Row_Pixel_Loop 25689 PUSH BC Stash the pixel line counter and room buffer pointer on the stack.
25690 PUSH HL
25691 LD D,H Copy the room buffer pointer to DE.
25692 LD E,L
25693 RES 7,D Reset bit 7 of D to convert from a room buffer address to the corresponding screen buffer address.
25695 LD BC,32 Copy 32 bytes from the room buffer to the screen buffer.
25698 LDIR
25700 POP HL Restore the room buffer pointer and pixel line counter from the stack.
25701 POP BC
25702 INC H Advance to the next pixel line in the room buffer.
25703 DJNZ Draw_Room_Row_Pixel_Loop Decrease the pixel line counter and loop back to Draw_Room_Row_Pixel_Loop until all 8 lines are copied.
Copy the colour attributes for this character row. Convert the room buffer address to the source and destination attribute buffer addresses.
25705 POP HL Restore the original room buffer pointer from the stack.
25706 LD A,H Rotate the high byte right three positions.
25707 RRCA
25708 RRCA
25709 RRCA
25710 AND %00000011 Mask to extract the character row index.
25712 OR %11011000 Set bits 3-4 and 6-7 to form the source attribute buffer high byte.
25714 LD H,A Set H to the source high byte and copy L to E.
25715 LD E,L
25716 LD A,H Mask the high byte again.
25717 AND %00000011
25719 OR %01011000 Set bits 3-4 and 6 to form the destination attribute buffer high byte.
25721 LD D,A Set D to the destination high byte.
25722 LD BC,32 Copy 0032 attribute bytes to the screen attribute buffer.
25725 LDIR
25727 RET Return.
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