Routines
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43716: Print Left Half Of Character
Used by the routine at PrintLargeText.
Draws the left half of four rows of a character in double size. The four bytes of pixels at DE each have their left four pixels widened to eight and written twice, so they fill the eight pixel rows of a character cell. The cell is coloured with the attribute and HL moves to the cell on its right.
Input
DE The address of the pixels of the character
HL The screen address
Output
HL The screen address of the cell to the right
Swap the pixels and the screen address.
PrintLeftHalfOfCharacter 43716 PUSH DE Stash the address of the pixels on the stack.
43717 PUSH HL Stash the screen address on the stack.
43718 EX DE,HL Swap the pixels into HL and the screen address into DE.
43719 LD B,4 Set the number of rows to four.
Widen the left four pixels of each row.
PrintLeftHalf_Loop 43721 LD A,(HL) Fetch a row of pixels.
43722 INC HL Move on to the next row.
43723 RRCA Move the left four pixels into the bottom of the byte.
43724 RRCA
43725 RRCA
43726 RRCA
43727 AND %00001111 Keep them.
43729 PUSH HL Stash the address of the pixels on the stack.
43730 LD HL,43784 Point HL at WidenedPixels.
43733 CALL AddAToHL Point HL at the entry for the four pixels.
43736 LD A,(HL) Fetch the widened pixels.
43737 LD (DE),A Write them to the screen.
43738 INC D Move down a pixel row.
43739 LD (DE),A Write them again.
43740 INC D Move down a pixel row.
43741 POP HL Retrieve the address of the pixels.
43742 DJNZ PrintLeftHalf_Loop Loop back until four rows have been drawn.
Colour the cell and move to the right.
43744 POP HL Retrieve the screen address.
43745 POP DE Retrieve the address of the pixels.
43746 CALL SetTileAttribute Set the attribute of the cell.
43749 INC L Move across to the next cell.
43750 RET Return.
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