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⌂ ∞ Elite on the BBC Micro and NES

Text: CHPR (Part 5 of 6)

[NES version, Bank 2]

       Name: CHPR (Part 5 of 6)                                      [Show more]
       Type: Subroutine
   Category: Text
    Summary: Print the character using a font that has already been loaded
  Deep dive: Fonts in NES Elite

    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file




.chpr22

                        ; If we get here then one of these is true:
                        ;
                        ;   * The normal and highlight fonts are loaded
                        ;     fontStyle = 2
                        ;     A = character number + 95
                        ;
                        ;   * The normal font is loaded
                        ;     fontStyle = 1
                        ;     A = character number

 PHA                    ; Store A on the stack to we can retrieve it after the
                        ; call to GetRowNameAddress

 JSR GetRowNameAddress  ; Get the addresses in the nametable buffers for the
                        ; start of character row YC, as follows:
                        ;
                        ;   SC(1 0) = the address in nametable buffer 0
                        ;
                        ;   SC2(1 0) = the address in nametable buffer 1

 PLA                    ; Retrieve the character number we stored on the stack
                        ; above

 CMP #' '               ; If we are printing a space, jump to chpr25
 BEQ chpr25

.chpr23

 CLC                    ; Convert the ASCII number in A to the pattern number in
 ADC asciiToPattern     ; the PPU of the corresponding character image, by
                        ; adding asciiToPattern (which gets set when the view
                        ; is set up)

.chpr24

 LDY XC                 ; Set Y to the column of the text cursor - 1
 DEY

 STA (SC),Y             ; Set the Y-th nametable entry in nametable buffer 0
                        ; for the Y-th character on row YC, to the pattern
                        ; number for our character from the loaded font

 STA (SC2),Y            ; Set the Y-th nametable entry in nametable buffer 1
                        ; for the Y-th character on row YC, to the pattern
                        ; number for our character from the loaded font

 JMP chpr17             ; Jump to chpr17 to return from the subroutine, as we
                        ; are done printing this character

.chpr25

                        ; If we get here then we are printing a space

 LDY QQ11               ; If the view type in QQ11 is $9D (Long-range Chart with
 CPY #$9D               ; the normal font loaded), jump to chpr26 to use pattern
 BEQ chpr26             ; 0 as the space character

 CPY #$DF               ; If the view type in QQ11 is not $DF (Start screen with
 BNE chpr23             ; the normal font loaded), jump to chpr23 to convert
                        ; the ASCII number in A to the pattern number

.chpr26

 LDA #0                 ; This is either view $9D (Long-range Chart) or $DF
                        ; (Start screen), and in both these views the normal
                        ; font is loaded directly into the PPU at a different
                        ; pattern number to the other views, so we set A = 0 to
                        ; use as the space character, as that is always a blank
                        ; tile

 BEQ chpr24             ; Jump up to chpr24 to draw the character (this BEQ is
                        ; effectively a JMP as A is always zero)