LIST command is now more foolproof

STATUS.md

@@ -22,6 +22,7 @@ Here are the features of the Open ROMs not found in the original ROMs from the 8
     * start/end addresses are displayed, in the Final cartridge style
     * command with just the file name tries to use the last device if it's number seems sane; otherwise uses 8
     * command without parameters tries to load first file from drive chosen as above
+* `LIST` command should never damage the screen if trying to list memory content which is not a BASIC program
 
 * uses RAM under ROM and I/O: 51199 bytes free (up to `$CFFF`) by default, but 61438 is also possible
 * cold/warm start silences multiple SID chips

src/basic/ab1e.strout.s

@@ -10,6 +10,7 @@
 // print string routine
 
 STROUT:
+
 	// Setup pointer
 	sty FRESPC+1
 	sta FRESPC+0

src/basic/assets/str_rev_question.s

@@ -0,0 +1,9 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+// String - question mark in reverse
+
+str_rev_question:
+
+	.byte $12, $3F, $92, $00

src/basic/board_m65/mega65_imports.s

@@ -23,3 +23,4 @@
 .label print_features                  = BASIC_0.proxy_B1_print_features
 #endif
 .label do_STRING_TOO_LONG_error        = BASIC_0.do_STRING_TOO_LONG_error
+.label str_rev_question                = BASIC_0.str_rev_question

src/basic/print/list_single_line.s

@@ -67,7 +67,9 @@ list_print_loop:
 	lda (OLDTXT),y
 #endif
 
-	beq list_end_of_line
+	bne !+
+	rts                                          // end of line
+!:
 	cmp #$22
 	bne list_not_quote
 	lda QTSW
@@ -118,6 +120,10 @@ list_display_token_CC:
 	// Subtract $1 from token to get offset in token list
 	dex
 
+	// Check if token is known
+	cpx #TK__MAXTOKEN_keywords_CC
+	bcs list_display_unknown_token               // XXX consider displaying two question marks here
+
 	// Now ask for it to be printed
 	jsr print_packed_keyword_CC
 
@@ -156,6 +162,10 @@ list_display_token_CD:
 	// Subtract $1 from token to get offset in token list
 	dex
 
+	// Check if token is known
+	cpx #TK__MAXTOKEN_keywords_CD
+	bcs list_display_unknown_token               // XXX consider displaying two question marks here
+
 	// Now ask for it to be printed
 	jsr print_packed_keyword_CD
 
@@ -174,9 +184,13 @@ list_display_token_V2:
 
 	// Subtract $80 from token to get offset in token list
 	txa
-	and #$7f
+	and #$7F
 	tax
 
+	// Check if token is known
+	cpx #TK__MAXTOKEN_keywords_V2
+	bcs list_display_unknown_token
+
 	// Now ask for it to be printed
 	jsr print_packed_keyword_V2
 
@@ -188,12 +202,14 @@ list_token_displayed:
 	ply_trash_a
 	pla
 
-	cmp #$8f
+	cmp #$8F
 	bne list_not_rem
 	// REM command locks quote flag on until the end of the line, allowing
 	// funny characters in REM statements without problem.
 	sta QTSW    // Any value other than $00 or $FF will lock quote mode on, so the token value of REM is fine here
-	// FALL THROUGH
+	
+	// FALLTHROUGH
+
 list_not_rem:		
 	
 	iny
@@ -205,13 +221,50 @@ list_is_pi:
 	// FALLTROUGH
 
 list_is_literal:
-	jsr JCHROUT
-	iny
-	bne list_print_loop
-	
-list_end_of_line:
-	
-	rts
 
+	pha
+	and #$7F
+	cmp #$12
+	beq list_is_literal_known                    // branch if quote mode on/off
+	and #%01100000
+	bne list_is_literal_known
+	pla
+
+	// FALLTROUGH
+
+list_is_unknown:
+
+	phy_trash_a
+	lda #<str_rev_question
+	ldy #>str_rev_question
+	jsr STROUT
+	ply_trash_a
+
+#if HAS_OPCODES_65C02
+	bra !+
+#else
+	jmp !+
+#endif
+
+list_is_literal_known:
+
+	pla
+	jsr JCHROUT
+!:
+	iny
+	bne_16 list_print_loop
+	
+	rts                                          // end of line
+
+list_display_unknown_token:
+
+	pla
+	pla
+
+#if HAS_OPCODES_65C02
+	bra list_is_unknown
+#else
+	jmp list_is_unknown
+#endif
 
 #endif // ROM layout