million-perfect-letters/src/ui.font.a

;license:MIT
;(c) 2020 by 4am
;
; font drawing routines
;

!macro COMPUTE_DRAW_ADDRESSES {
         ldx   charrow
         lda   HGRLO, x
         sta   $F0
         sta   $F2
         inc   $F2
         lda   HGRHI, x
         sta   $F1                   ; ($F0) -> base address of top row to draw (used for upper-left block of each character)
         sta   $F3                   ; ($F2) -> base address + 1 of top row to draw (used for upper-right block of each character)
         ldx   char                  ; X = 0-based index into LeftFontRow0 array for the character we're drawing
         ldy   HTAB
}

!macro INC_AND_RECOMPUTE_DRAW_ADDRESSES {
         inc   charrow
         +COMPUTE_DRAW_ADDRESSES
}

DrawCharacter
; A contains character (0x41..0x5A)
; X contains logical line number (0x00..0x08)
; Y contains logical column number (0x00..0x0C)
; HGR row is (0x16 * X)
;   which needs to total no more than 0xB0
; character will be drawn on HGR row, byte offset (GlobalLeftMargin + (3 * Y))
;   which needs to total no more than 0x26
; preserves X/Y
; clobbers A/all flags
; clobbers $ED..$F7
         sta   original_char
         and   #$7F
         sec
         sbc   #$41
         bpl   +
         rts
+        sta   char
         stx   @x+1
         sty   @y+1
         jsr   LogicalColumnToPhysicalColumn
         sty   HTAB
         lda   #$00
         clc
         bcc   +
-        adc   #$16
+        dex
         bpl   -
         sta   charrow

         +COMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow0, x       ; draw row 0, byte 0
         sta   ($F0), y
         lda   RightFontRow0, x      ; draw row 0, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow1, x       ; draw row 1, byte 0
         sta   ($F0), y
         lda   RightFontRow1, x      ; draw row 1, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow2, x       ; draw row 2, byte 0
         sta   ($F0), y
         lda   RightFontRow2, x      ; draw row 2, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow3, x       ; draw row 3, byte 0
         sta   ($F0), y
         lda   RightFontRow3, x      ; draw row 3, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow4, x       ; draw row 4, byte 0
         sta   ($F0), y
         lda   RightFontRow4, x      ; draw row 4, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow5, x       ; draw row 5, byte 0
         sta   ($F0), y
         lda   RightFontRow5, x      ; draw row 5, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow6, x       ; draw row 6, byte 0
         sta   ($F0), y
         lda   RightFontRow6, x      ; draw row 6, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow7, x       ; draw row 7, byte 0
         sta   ($F0), y
         lda   RightFontRow7, x      ; draw row 7, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow8, x       ; draw row 8, byte 0
         sta   ($F0), y
         lda   RightFontRow8, x      ; draw row 8, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow9, x       ; draw row 9, byte 0
         sta   ($F0), y
         lda   RightFontRow9, x      ; draw row 9, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow10, x       ; draw row 10, byte 0
         sta   ($F0), y
         lda   RightFontRow10, x      ; draw row 10, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow11, x       ; draw row 11, byte 0
         sta   ($F0), y
         lda   RightFontRow11, x      ; draw row 11, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow12, x       ; draw row 12, byte 0
         sta   ($F0), y
         lda   RightFontRow12, x      ; draw row 12, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow13, x       ; draw row 13, byte 0
         sta   ($F0), y
         lda   RightFontRow13, x      ; draw row 13, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         lda   LeftFontRow14, x       ; draw row 14, byte 0
         sta   ($F0), y
         lda   RightFontRow14, x      ; draw row 14, byte 1
         sta   ($F2), y

         +INC_AND_RECOMPUTE_DRAW_ADDRESSES
         bit   original_char
         bmi   +
         lda   LeftFontRow15, x       ; draw row 15, byte 0
         sta   ($F0), y
         lda   RightFontRow15, x      ; draw row 15, byte 1
         sta   ($F2), y
         jmp   ++
+        lda   #0
         sta   ($F0), y
         sta   ($F2), y
++
@x       ldx   #$FD                   ; SMC
@y       ldy   #$FD                   ; SMC
         rts