print the cancel character for ^X and ^Z.

based on testing, this applies to vt52 and vt100.
use the current x pos to choose between $56 and $57 (mouse text checkerboard)
so multiple characters look pretty.

vt100.ctrl.S

@@ -109,8 +109,11 @@ xoff
 	rts
 can
 sub
+	ext draw_char_raw
 * cancel esc sequence and display error character
 	stz state
+	lda #$57 ; mouse text block
+	jmp draw_char_raw
 	rts
 
 esc

vt100.main.S

@@ -214,7 +214,7 @@ vt100
 	ext vt100_esc,vt100_csi,vt100_csi_2
 	ext vt100_esc_pound,vt100_esc_lparen,vt100_esc_rparen
 	ext vt100_esc_bad,vt100_csi_bad
-	ext draw_char
+	ext draw_char,draw_char_raw
 
 	dw draw_char
 	dw vt52_esc
@@ -290,7 +290,16 @@ ctrl_18
 ctrl_1a
 * vt100 - abort current escape sequence
 * and display error character.
-* TODO - display error character (mouse text)
+*
+* based on testing, this applies to vt52 and vt100;
+* cancel character is drawn regardless of current state.
+
+	lda x
+	and #$1
+	ora #$56 ; $56 or $57
+*	lda #$57
+	jsr draw_char_raw
+
 	bit DECANM
 	bpl :vt52
 	lda #st_vt100

vt100.screen.S

@@ -236,16 +236,20 @@ draw_char ent
 	bpl :normal
 ; invert it.
 	cmp #$60 ; `, first lowercase
-	bge :draw ; nothing to do for lowercase
+	bge draw_char_raw ; nothing to do for lowercase
 	cmp #$40 ; @, first uppercase
-	bcc :draw ; nothing to do for special
+	bcc draw_char_raw ; nothing to do for special
 
 :uc	and #%10111111 ; ~ $40
-	bra :draw
+	bra draw_char_raw
 
 
 :normal	ora #$80
-:draw
+
+draw_char_raw ent
+* entry point for writing character to screen w/o processing it
+
+
 *	sta cursor_saved_char
 
 * with DECAWM, x = 79, will CR LF (with scroll) before drawing character.
@@ -280,8 +284,6 @@ draw_char ent
 	rts
 
 
-
-
 :wrap
 	stz x
 	ldy y