Identify SET_TEXT_MASK

desk.acc/a2d.inc

@@ -108,10 +108,11 @@ A2D_SET_THICKNESS := $0A
         ;; .byte hthick         horizontal pen thickness
         ;; .byte vthick         vertical pen thickness
 
-A2D_UNK_0C      := $0C          ; Unknown - used in calculator
+A2D_SET_TEXT_MASK := $0C        ; Stored to background before XORing glyph
         ;; (input length 1 byte)
+        ;; .byte mask
 
-A2D_SET_POS     := $0E
+A2D_SET_POS     := $0E          ; Start of subsequent DRAW_TEXT, DRAW_LINE
         ;; (input length 4 bytes)
         ;; .word xcoord
         ;; .word ycoord

desk.acc/calculator.s

@@ -574,8 +574,9 @@ white_pattern:
         .res    8, $FF
         .byte   $00
 
-        ;; arg for $0C call ???
-L0BEF:  .byte   $7F
+.proc text_mask_params
+mask:  .byte   $7F
+.endproc
 
         display_left    := 10
         display_top     := 5
@@ -1591,8 +1592,7 @@ loop:   lda     #' '
         A2D_CALL A2D_DRAW_RECT, frame_display_params
         A2D_CALL A2D_SET_PATTERN, white_pattern
         A2D_CALL A2D_FILL_RECT, clear_display_params
-
-        A2D_CALL $0C, L0BEF     ; ???
+        A2D_CALL A2D_SET_TEXT_MASK, text_mask_params
         ;; fall through
 .endproc
 

desk.acc/date.s

@@ -172,8 +172,11 @@ month_rect:
 year_rect:
         .word   $7F,$14,$95,$1E
 
-        ;; Params for $0C call (1 byte?)
-L08FC:  .res    8, $00
+.proc text_mask_params
+mask:   .byte   0
+.endproc
+
+        .res    7, $00          ; ???
         .byte   $FF
 
 .proc white_pattern
@@ -529,7 +532,7 @@ go:     lda     selected_field
         sta     gosub+2
 
 gosub:  jsr     $1000           ; self modified
-        A2D_CALL $0C, L08FC
+        A2D_CALL A2D_SET_TEXT_MASK, text_mask_params
         jmp     draw_selected_field
 .endproc