Routines
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869B: Print: Write A Character To The Screen
Writes one character into the text window, scrolling when the line is full.
PrintWriteACharacterToTheScreen 869B DEFB $00
869C DEFW $0000
869E DEFB $00
869F DEFB $00
86A0 DEFB $00
This entry point is used by the routine at Print_Character.
PrintWriteACharacterToTheScreen_0 86A1 PUSH HL Save HL, BC and AF, and bring HL back from 869C.
86A2 PUSH BC
86A3 PUSH AF
86A4 LD HL,($869C)
86A7 LD A,($869E) Read the print column.
86AA LD C,A Copy the result into C.
Test this flag.
86AB LD A,($86A0) Jump to PrintWriteACharacterToTheScreen_TestForAReturn if *86A0 is not zero.
86AE AND A
86AF JR NZ,PrintWriteACharacterToTheScreen_TestForAReturn
Test this flag.
86B1 LD A,($869F) Jump to PrintWriteACharacterToTheScreen_TestForAReturn if *869F is zero.
86B4 AND A
86B5 JR Z,PrintWriteACharacterToTheScreen_TestForAReturn
86B7 LD B,A Copy the result into B.
PrintWriteACharacterToTheScreen_Loop 86B8 LD A,$20 Use the character ' '.
Draw this character with the game font.
86BA CALL Print_ProportionalCharacter Call Print_ProportionalCharacter to draw this character with the game's font.
86BD LD A,($869B) Read the room left on the line at PrintWriteACharacterToTheScreen.
86C0 DEC A Drop one from the room left on the line.
86C1 LD ($869B),A Update the room left on the line.
86C4 DJNZ PrintWriteACharacterToTheScreen_Loop Loop back to PrintWriteACharacterToTheScreen_Loop until the space count runs out.
PrintWriteACharacterToTheScreen_TestForAReturn 86C6 POP AF Restore the character from the stack, keeping a copy there.
86C7 PUSH AF
86C8 CP $0D Jump to PrintWriteACharacterToTheScreen_TestBackspace unless the character is 0D.
86CA JR NZ,PrintWriteACharacterToTheScreen_TestBackspace
86CC LD A,$01 Set the capitalise-the-next-letter flag after a carriage return.
86CE LD ($B704),A
PrintWriteACharacterToTheScreen_ClearTheFlag 86D1 XOR A Clear *86A0.
86D2 LD ($86A0),A
86D5 CALL ZXPrinter Call ZXPrinter to copy this text line to the ZX printer.
86D8 PUSH BC Save BC.
Test how many words will be accepted.
86D9 LD A,($B716) Jump to PrintWriteACharacterToTheScreen_CountDownTheWords if *B716 is not zero.
86DC AND A
86DD JR NZ,PrintWriteACharacterToTheScreen_CountDownTheWords
86DF LD BC,$8000 Point BC at 8000.
PrintWriteACharacterToTheScreen_PollKeys 86E2 XOR A Select every keyboard row.
86E3 IN A,($FE) Read port FE into A.
86E5 AND $1F Jump to PrintWriteACharacterToTheScreen_DropTheTimeout unless the low five bits are all set.
86E7 CP $1F
86E9 JR NZ,PrintWriteACharacterToTheScreen_DropTheTimeout
86EB DEC BC Loop back to PrintWriteACharacterToTheScreen_PollKeys until the keyboard timeout reaches zero.
86EC LD A,B
86ED OR C
86EE JR NZ,PrintWriteACharacterToTheScreen_PollKeys
86F0 POP BC Jump to PrintWriteACharacterToTheScreen_PointAtTheTextLine to scroll line.
86F1 JR PrintWriteACharacterToTheScreen_PointAtTheTextLine
PrintWriteACharacterToTheScreen_CountDownTheWords 86F3 DEC A Count down how many words will be accepted.
86F4 LD ($B716),A Update *B716.
PrintWriteACharacterToTheScreen_DropTheTimeout 86F7 POP BC Drop the timeout and select every keyboard row.
PrintWriteACharacterToTheScreen_WaitForRelease 86F8 XOR A
86F9 IN A,($FE) Read port FE into A.
86FB AND $1F Jump back to PrintWriteACharacterToTheScreen_WaitForRelease unless the low five bits are all set.
86FD CP $1F
86FF JR NZ,PrintWriteACharacterToTheScreen_WaitForRelease
PrintWriteACharacterToTheScreen_PointAtTheTextLine 8701 LD HL,$5020 Point HL at the text line.
8704 LD C,$01 One pixel row of the character.
8706 CALL ScrollLine Call ScrollLine to scroll line.
8709 LD A,$2A Reset the room left on the line to 2A.
870B JR PrintWriteACharacterToTheScreen_StoreTheRoomLeft Jump to PrintWriteACharacterToTheScreen_StoreTheRoomLeft to store the room left on the line.
PrintWriteACharacterToTheScreen_TestBackspace 870D CP $08 Jump to PrintWriteACharacterToTheScreen_TestForALetter if the character is not 08.
870F JR NZ,PrintWriteACharacterToTheScreen_TestForALetter
8711 CALL Print_WrapTheColumn Call Print_WrapTheColumn to wrap the print column.
8714 LD A,$20 Use the character ' '.
Draw this character with the game font.
8716 CALL Print_ProportionalCharacter Call Print_ProportionalCharacter to draw this character with the game's font.
8719 CALL Print_WrapTheColumn Call Print_WrapTheColumn to wrap the print column.
871C LD A,($869B) Read the room left on the line at PrintWriteACharacterToTheScreen.
871F INC A Count one more character on the line.
8720 JR PrintWriteACharacterToTheScreen_StoreTheRoomLeft Jump to PrintWriteACharacterToTheScreen_StoreTheRoomLeft to store the room left on the line.
PrintWriteACharacterToTheScreen_TestForALetter 8722 CP $41 Jump to PrintWriteACharacterToTheScreen_TestCapitalise if the character is below 41.
8724 JR C,PrintWriteACharacterToTheScreen_TestCapitalise
8726 CP $5B Jump to PrintWriteACharacterToTheScreen_TestCapitalise if the character is 5B or above.
8728 JR NC,PrintWriteACharacterToTheScreen_TestCapitalise
872A OR $20 Merge in 20.
PrintWriteACharacterToTheScreen_TestCapitalise 872C PUSH HL Point HL at the capitalise-the-next-letter flag.
872D LD HL,$B704
8730 INC (HL) Test the capitalise-the-next-letter flag without changing it.
8731 DEC (HL)
8732 JR Z,PrintWriteACharacterToTheScreen_TestForAFullStop Jump to PrintWriteACharacterToTheScreen_TestForAFullStop if the next letter should not be capitalised.
8734 CP $61 Jump to PrintWriteACharacterToTheScreen_TestForAFullStop if the character is below 61.
8736 JR C,PrintWriteACharacterToTheScreen_TestForAFullStop
8738 CP $7B Jump to PrintWriteACharacterToTheScreen_TestForAFullStop if it is 7B or above.
873A JR NC,PrintWriteACharacterToTheScreen_TestForAFullStop
873C RES 5,A Clear bit 5.
873E LD (HL),$00 Clear the capitalise-the-next-letter flag once the letter is upper case.
PrintWriteACharacterToTheScreen_TestForAFullStop 8740 CP $2E Jump to PrintWriteACharacterToTheScreen_DrawTheGlyph unless it is 2E.
8742 JR NZ,PrintWriteACharacterToTheScreen_DrawTheGlyph
8744 INC (HL) A full stop bumps the capitalise-the-next-letter flag.
PrintWriteACharacterToTheScreen_DrawTheGlyph 8745 POP HL Pop the screen address and call Print_ProportionalCharacter to draw the glyph.
Draw this character with the game font.
8746 CALL Print_ProportionalCharacter
8749 LD ($86A0),A Store the column and jump back to PrintWriteACharacterToTheScreen_ClearTheFlag when the room left on the line reaches zero.
874C LD A,($869B)
874F DEC A
8750 JP Z,PrintWriteACharacterToTheScreen_ClearTheFlag
PrintWriteACharacterToTheScreen_StoreTheRoomLeft 8753 LD ($869B),A Update the room left on the line.
8756 LD ($869C),HL Store HL at 869C.
8759 LD A,C Store the print column.
875A LD ($869E),A
875D POP AF Restore AF, BC and HL from the stack.
875E POP BC
875F POP HL
8760 RET Return.
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