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Routines |
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| 30042 | XOR A | Clear the buffer ready for writing | ||||||||||
| 30043 | LD B,64 | |||||||||||
| 30045 | LD (DE),A | |||||||||||
| 30046 | INC DE | |||||||||||
| 30047 | DJNZ 30045 | |||||||||||
| 30049 | DEC DE | Point DE at the last byte of the buffer | ||||||||||
| 30050 | LD C,62 | There are 62 pixel columns available for writing in | ||||||||||
| 30052 | LD A,(HL) | Pick up a character from the message in A | ||||||||||
| 30053 | INC HL | Move to the next character in the message | ||||||||||
| 30054 | AND A | Have we reached the end of the message? | ||||||||||
| 30055 | JR Z,30079 | Jump if so | ||||||||||
| 30057 | PUSH HL | Save the message pointer | ||||||||||
| 30058 | LD L,A | Point HL at the pixel width of the bitmap for the character in A | ||||||||||
| 30059 | LD H,217 | |||||||||||
| 30061 | LD A,(HL) | Pick up the width in A | ||||||||||
| 30062 | LD B,A | Transfer the width to B | ||||||||||
| 30063 | INC H | Point HL at the next font character bitmap byte | ||||||||||
| 30064 | LD A,(HL) | Pick this up in A | ||||||||||
| 30065 | CALL 30097 | Insert the font character bitmap byte into the buffer | ||||||||||
| 30068 | DEC C | Decrease the pixel column count | ||||||||||
| 30069 | DJNZ 30063 | Jump back until all pixel columns for this letter are done | ||||||||||
| 30071 | XOR A | A=0 (empty vertical pixel column, i.e. space) | ||||||||||
| 30072 | DEC C | Decrease the pixel column count | ||||||||||
| 30073 | CALL 30097 | Insert the space into the buffer | ||||||||||
| 30076 | POP HL | Restore the message pointer to HL | ||||||||||
| 30077 | JR 30052 | Jump back to write the next letter from the message | ||||||||||
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We've finished writing the message. Now centre it.
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| 30079 | BIT 7,C | Did we use more than 62 pixel columns? | ||||||||||
| 30081 | RET NZ | Return if so | ||||||||||
| 30082 | RR C | C holds the number of unused pixel columns; halve this and add one to get the padding | ||||||||||
| 30084 | INC C | |||||||||||
| 30085 | XOR A | Insert an empty pixel column (space) | ||||||||||
| 30086 | CALL 30097 | |||||||||||
| 30089 | DEC C | Next column of padding | ||||||||||
| 30090 | JR NZ,30085 | Jump back until the text has been centred | ||||||||||
| 30092 | RET | |||||||||||
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