// Shows a font where each char contains the number of the char (00-ff)
/// @file
/// Commodore 64 Registers and Constants
/// @file
/// The MOS 6526 Complex Interface Adapter (CIA)
///
/// http://archive.6502.org/datasheets/mos_6526_cia_recreated.pdf
  // Commodore 64 PRG executable file
.file [name="font-hex-show.prg", type="prg", segments="Program"]
.segmentdef Program [segments="Basic, Code, Data"]
.segmentdef Basic [start=$0801]
.segmentdef Code [start=$80d]
.segmentdef Data [startAfter="Code"]
.segment Basic
:BasicUpstart(main)
  /// $D018 VIC-II base addresses
  // @see #VICII_MEMORY
  .label D018 = $d018
  .label SCREEN = $400
  .label CHARSET = $2000
.segment Code
main: {
    .const toD0181_return = (>(SCREEN&$3fff)*4)|(>CHARSET)/4&$f
    // *D018 = toD018(SCREEN, CHARSET)
    lda #toD0181_return
    sta D018
    // init_font_hex(CHARSET)
    jsr init_font_hex
    ldx #0
  // Show all chars on screen
  __b1:
    // SCREEN[c] = c
    txa
    sta SCREEN,x
    // for (byte c: 0..255)
    inx
    cpx #0
    bne __b1
    // }
    rts
}
// Make charset from proto chars
// void init_font_hex(__zp(5) char *charset)
init_font_hex: {
    .label __0 = $b
    .label idx = $a
    .label proto_lo = 7
    .label charset = 5
    .label c1 = 9
    .label proto_hi = 2
    .label c = 4
    lda #0
    sta.z c
    lda #<FONT_HEX_PROTO
    sta.z proto_hi
    lda #>FONT_HEX_PROTO
    sta.z proto_hi+1
    lda #<CHARSET
    sta.z charset
    lda #>CHARSET
    sta.z charset+1
  __b1:
    lda #0
    sta.z c1
    lda #<FONT_HEX_PROTO
    sta.z proto_lo
    lda #>FONT_HEX_PROTO
    sta.z proto_lo+1
  __b2:
    // charset[idx++] = 0
    lda #0
    tay
    sta (charset),y
    lda #1
    sta.z idx
    ldx #0
  __b3:
    // proto_hi[i]<<4
    txa
    tay
    lda (proto_hi),y
    asl
    asl
    asl
    asl
    sta.z __0
    // proto_lo[i]<<1
    txa
    tay
    lda (proto_lo),y
    asl
    // proto_hi[i]<<4 | proto_lo[i]<<1
    ora.z __0
    // charset[idx++] = proto_hi[i]<<4 | proto_lo[i]<<1
    ldy.z idx
    sta (charset),y
    // charset[idx++] = proto_hi[i]<<4 | proto_lo[i]<<1;
    inc.z idx
    // for( byte i: 0..4)
    inx
    cpx #5
    bne __b3
    // charset[idx++] = 0
    lda #0
    ldy.z idx
    sta (charset),y
    // charset[idx++] = 0;
    iny
    // charset[idx++] = 0
    sta (charset),y
    // proto_lo += 5
    lda #5
    clc
    adc.z proto_lo
    sta.z proto_lo
    bcc !+
    inc.z proto_lo+1
  !:
    // charset += 8
    lda #8
    clc
    adc.z charset
    sta.z charset
    bcc !+
    inc.z charset+1
  !:
    // for( byte c: 0..15 )
    inc.z c1
    lda #$10
    cmp.z c1
    bne __b2
    // proto_hi += 5
    lda #5
    clc
    adc.z proto_hi
    sta.z proto_hi
    bcc !+
    inc.z proto_hi+1
  !:
    // for( byte c: 0..15 )
    inc.z c
    lda #$10
    cmp.z c
    bne __b1
    // }
    rts
}
.segment Data
  // Bit patterns for symbols 0-f (3x5 pixels) used in font hex
  FONT_HEX_PROTO: .byte 2, 5, 5, 5, 2, 6, 2, 2, 2, 7, 6, 1, 2, 4, 7, 6, 1, 2, 1, 6, 5, 5, 7, 1, 1, 7, 4, 6, 1, 6, 3, 4, 6, 5, 2, 7, 1, 1, 1, 1, 2, 5, 2, 5, 2, 2, 5, 3, 1, 1, 2, 5, 7, 5, 5, 6, 5, 6, 5, 6, 2, 5, 4, 5, 2, 6, 5, 5, 5, 6, 7, 4, 6, 4, 7, 7, 4, 6, 4, 4