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Routines |
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755A | XOR A | Clear the buffer ready for writing | ||||||||||
755B | LD B,$40 | |||||||||||
755D | LD (DE),A | |||||||||||
755E | INC DE | |||||||||||
755F | DJNZ $755D | |||||||||||
7561 | DEC DE | Point DE at the last byte of the buffer | ||||||||||
7562 | LD C,$3E | There are 62 pixel columns available for writing in | ||||||||||
7564 | LD A,(HL) | Pick up a character from the message in A | ||||||||||
7565 | INC HL | Move to the next character in the message | ||||||||||
7566 | AND A | Have we reached the end of the message? | ||||||||||
7567 | JR Z,$757F | Jump if so | ||||||||||
7569 | PUSH HL | Save the message pointer | ||||||||||
756A | LD L,A | Point HL at the pixel width of the bitmap for the character in A | ||||||||||
756B | LD H,$D9 | |||||||||||
756D | LD A,(HL) | Pick up the width in A | ||||||||||
756E | LD B,A | Transfer the width to B | ||||||||||
756F | INC H | Point HL at the next font character bitmap byte | ||||||||||
7570 | LD A,(HL) | Pick this up in A | ||||||||||
7571 | CALL $7591 | Insert the font character bitmap byte into the buffer | ||||||||||
7574 | DEC C | Decrease the pixel column count | ||||||||||
7575 | DJNZ $756F | Jump back until all pixel columns for this letter are done | ||||||||||
7577 | XOR A | A=0 (empty vertical pixel column, i.e. space) | ||||||||||
7578 | DEC C | Decrease the pixel column count | ||||||||||
7579 | CALL $7591 | Insert the space into the buffer | ||||||||||
757C | POP HL | Restore the message pointer to HL | ||||||||||
757D | JR $7564 | Jump back to write the next letter from the message | ||||||||||
We've finished writing the message. Now centre it.
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757F | BIT 7,C | Did we use more than 62 pixel columns? | ||||||||||
7581 | RET NZ | Return if so | ||||||||||
7582 | RR C | C holds the number of unused pixel columns; halve this and add one to get the padding | ||||||||||
7584 | INC C | |||||||||||
7585 | XOR A | Insert an empty pixel column (space) | ||||||||||
7586 | CALL $7591 | |||||||||||
7589 | DEC C | Next column of padding | ||||||||||
758A | JR NZ,$7585 | Jump back until the text has been centred | ||||||||||
758C | RET |
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