From af1f5b079d885bb5cbf7898ab7e18c47056c664a Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Wed, 12 Feb 2020 20:37:10 +0100
Subject: [PATCH] fixed screen code to PETSCII conversion

---
 .../screen/chrout_screen_jumptable_codes.s    |  6 +-
 c64/kernal/screen/screen_code_to_petscii.s    | 79 +++++++++++++------
 2 files changed, 60 insertions(+), 25 deletions(-)

diff --git a/c64/kernal/screen/chrout_screen_jumptable_codes.s b/c64/kernal/screen/chrout_screen_jumptable_codes.s
index 303c48c4..66e56e74 100644
--- a/c64/kernal/screen/chrout_screen_jumptable_codes.s
+++ b/c64/kernal/screen/chrout_screen_jumptable_codes.s
@@ -94,6 +94,8 @@ chrout_screen_jumptable_hi:
 
 #else
 
+__before_chrout_screen_jumptable:
+
 .if (mod(*, $2) == 1) { brk }          // align code so that vector never crosses page boundary
 
 chrout_screen_jumptable:
@@ -121,6 +123,8 @@ chrout_screen_jumptable:
 	.word chrout_screen_DEL
 	.word chrout_screen_RETURN
 
-.if (mod(*, $2) == 0) { brk }          // make sure routine size is always the same, needed by build system
+	// Make sure routine size is always the same - build system limitation
+
+.if (__before_chrout_screen_jumptable == chrout_screen_jumptable) { brk }
 
 #endif
diff --git a/c64/kernal/screen/screen_code_to_petscii.s b/c64/kernal/screen/screen_code_to_petscii.s
index 4b0e00ad..1a66bff6 100644
--- a/c64/kernal/screen/screen_code_to_petscii.s
+++ b/c64/kernal/screen/screen_code_to_petscii.s
@@ -3,42 +3,73 @@
 // #LAYOUT# *   KERNAL_0 #TAKE
 // #LAYOUT# *   *        #IGNORE
 
+//
+// Screen code to PETSCII conversion - see:
+//
+// - https://www.lemon64.com/forum/viewtopic.php?t=66362
+// - https://sta.c64.org/cbm64scrtopetext.html
+//
 
-// XXX - conversion should depend on QTSW too
+
+// XXX - part below might depend on QTSW too
 
 
 screen_code_to_petscii:
-	cmp #$1B
-	bcc s2p_adc_40
-	
-s2p_not_alpha:
+
+	cmp #$20
+	bcc s2p_adc_40                     // $00-$1F -> $40-$5F
+
 	cmp #$40
-	bcc s2p_end
+	bcc s2p_end                        // $20-$3F -> $20-$3F
 
-	// FALLTROUGH
-
-s2p_not_punctuation:
-	cmp #$5B
-	bcs s2p_not_shifted
-
-	// carry already clear here
-	adc #$80
-
-	rts
-
-s2p_not_shifted:
+	cmp #$60
+	bcc s2p_adc_80                     // $40-$5F -> $C0-$DF
 
 	cmp #$80
-	bcs s2p_end // not vendor
+	bcc s2p_adc_40                     // $60-$7F -> $A0-$BF
 
-	// $60-$7F -> $A0-$BF
+	// Here we have to check for quote mode
+
+	bit QTSW
+	bmi screen_code_to_petscii_quote
+
+	// Not quote mode - continue
+
+	cmp #$A0
+	bcc s2p_adc_C0                     // $80-$9F -> $40-$5F
+
+	cmp #$C0
+	bcc s2p_adc_80                     // $A0-$BF -> $20-$3F
+
+	cmp #$E0
+	bcc s2p_end                        // $C0-$DF -> $C0-$DF
+
+	clc
+	bcc s2p_adc_C0                     // $E0-$FF -> $A0-$BF
 
 s2p_adc_40:
 
-	clc
-	adc #$40
-	
-	// FALLTROUGH
+	adc #$40                           // Carry already clear
 
 s2p_end:
+
+	rts
+
+s2p_adc_80:
+
+	adc #$80                           // Carry already clear
+	rts
+
+screen_code_to_petscii_quote:
+
+	cmp #$C0
+	bcc s2p_adc_80                     // $80-$BF -> $00-$3F
+
+	clc
+
+	// FALLTROUGH                         $C0-$FF -> $80-$BF
+
+s2p_adc_C0:
+
+	adc #$C0                           // Carry already clear
 	rts