From 6e0de284e08c3f78c43ca3d4a8e3aaf89717f04e Mon Sep 17 00:00:00 2001
From: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri, 17 Sep 2021 19:50:56 -0400
Subject: [PATCH] more vt100 code

to handle DECAWM mode, bit 7 of x ($80 + 79) indicates a wrap is imminent, as opposed to just being in column 79. backspace, etc will drop back to column 78 (based on testing).
---
 vt.equ.S     | 13 +++++++++++--
 vt100.csi.S  |  2 ++
 vt100.ctrl.S |  5 ++++-
 vt100.esc.S  |  6 +++++-
 vt100.link.S | 23 +++++++++++++----------
 vt100.main.S | 20 +++++++++++++-------
 vt100.tabs.S | 32 ++++++++++++++++----------------
 vt100.vt52.S | 20 +++++++++++++-------
 8 files changed, 77 insertions(+), 44 deletions(-)

diff --git a/vt.equ.S b/vt.equ.S
index 9953a30..57798d4 100644
--- a/vt.equ.S
+++ b/vt.equ.S
@@ -20,6 +20,7 @@ ESC	equ $1b
 state	ds 2
 x	ds 2
 y	ds 2
+
 DECTM	ds 2 ; top margin
 DECBM	ds 2 ; bottom margin
 
@@ -55,10 +56,18 @@ pcount	ds	2
 parms	ds	MAX_PCOUNT
 pmod	ds	2
 
+; scratch registers
 r0	ds	2
 
-* saved character for cursor 
-cursor_saved_char ds 2
+
+cursor_saved_char ds 2 ; saved char under the cursor
+cursor_base	ds 4
+cursor_offset	ds 2
+cursor_char	ds 2 ; cursor character
+cursor_state	ds 2 ; on/off/disabled.
+
+draw_inverse	ds 2 ; flag to draw inverse
+erase_char	ds 2 ; clear character
 
 	do *>256
 	err "too big"
diff --git a/vt100.csi.S b/vt100.csi.S
index ba27811..973fe1d 100644
--- a/vt100.csi.S
+++ b/vt100.csi.S
@@ -9,6 +9,8 @@
 
 	use vt.equ
 
+	mx %11
+
 	ext update_cursor,reset_tab,reset_all_tabs
 
 vt100_csi ent
diff --git a/vt100.ctrl.S b/vt100.ctrl.S
index 2e11178..46851b0 100644
--- a/vt100.ctrl.S
+++ b/vt100.ctrl.S
@@ -67,12 +67,15 @@ bs
 * backspace, no wrap
 	lda x
 	beq :rts
-	dec x
+	and #$7f
+	dec
+	sta x
 	jmp update_cursor
 :rts	rts
 
 tab
 * go to next tab stop
+* tab at 80 does not reset overflow.
 	rts
 
 lf
diff --git a/vt100.esc.S b/vt100.esc.S
index 2876090..7fe4607 100644
--- a/vt100.esc.S
+++ b/vt100.esc.S
@@ -6,6 +6,9 @@
 
 	use vt.equ
 
+	mx %11
+
+
 vt100_esc ent
 * #[()=>cH78DEM
 * based on testing, unspecified chars in the 0x20-0x2f range cause it to gobble
@@ -13,7 +16,6 @@ vt100_esc ent
 
 * esc 1 -> hangs? [undocumented]
 
-
 	ldx #st_vt100
 	stx state
 
@@ -137,7 +139,9 @@ esc_gt ; exit alternate keypad mode
 esc_H ; set tab stop
 	ext set_tab
 	ldx x
+	bmi :rts
 	jmp set_tab
+:rts	rts
 
 esc_E ; next line
 	stz x
diff --git a/vt100.link.S b/vt100.link.S
index 6276036..eeb4c38 100644
--- a/vt100.link.S
+++ b/vt100.link.S
@@ -1,22 +1,25 @@
 
 	ovr all
-
 * binary linker
 	lkv 0
 	org $6000
 
-	asm boot.S
-	asm vt100.ctrl.S
+*	asm boot.S
+*	asm vt100.ctrl.S
+	asm vt100.esc.S
+	asm vt100.tabs.S
+	asm vt100.vt52.S
+	asm vt100.csi.S
+	asm vt100.screen.S
 
 
-
-	lnk boot.S
-	pos ; reset
+*	lnk boot.S
+*	pos ; reset
 
 
-	pos EMU_SIZE
-EMU_SIZE	ext 
-EMU_BLOCKS	geq EMU_SIZE+511\512
+*	pos EMU_SIZE
+*EMU_SIZE	ext 
+*EMU_BLOCKS	geq EMU_SIZE+511\512
 
 
-	sav vt100.bin
\ No newline at end of file
+*	sav vt100.bin
\ No newline at end of file
diff --git a/vt100.main.S b/vt100.main.S
index 3a873df..3a80fd7 100644
--- a/vt100.main.S
+++ b/vt100.main.S
@@ -104,6 +104,7 @@ ctrl_18
 ctrl_1a
 * vt100 - abort current escape sequence
 * and display error character.
+* TODO - display error character (mouse text)
 	lda DECANM
 	bne :vt52
 	lda #st_vt100
@@ -116,9 +117,11 @@ ctrl_1a
 	rts
 
 ctrl_08 ; back space
-	ldx x
+	lda x
 	beq :rts
-	dec x
+	and #$7f
+	dec
+	sta x
 	jmp update_cursor
 :rts
 
@@ -126,9 +129,11 @@ ctrl_09 ; tab
 * vt100 has adjustable tabs.
 	ext next_tab_stop
 	ldx x
+	bmi :rts
 	jsr next_tab_stop
 	stx x
 	jmp update_cursor
+:rts rts
 
 ctrl_0a ; line feed - cursor down w/ scroll
 ctrl_0b ; vertical tab
@@ -136,18 +141,19 @@ ctrl_0c ; form feed.
 
 * if LNM is active, equivalent to CR, LF
 
-	lda #LNM
-	bne :lnm
+	bit #LNM
+	bpl :lf
 	stz x
-:lnm
 
+:lf
 	lda y
-	cmp #23
+	cmp #DECBM
 	blt :simple
 
-	lda #" "
+	lda #" " ; needs to factor in reverse video
 	sta cursor_saved_char
 	jmp scroll_down
+* if LNM mode, need to update cursor as well.
 
 :simple
 	inc y
diff --git a/vt100.tabs.S b/vt100.tabs.S
index 5e21e12..46f4616 100644
--- a/vt100.tabs.S
+++ b/vt100.tabs.S
@@ -1,30 +1,29 @@
 
-
+	lst off
 	rel
 	xc
 	xc
 
 	use vt.equ
 
+	mx %11
 
 init_tabs	ent
 
-
-	ldx #80
-:loop	stz tabs,x
+	ldx #80-1
+:zloop	stz tabs,x
 	dex
+	bpl :zloop
+
+	lda #$80
+	ldy #8
+:loop	ldx :table,y
+	sta tabs,x
+	dey
 	bpl :loop
 
-	lda #72
-	ldy #$80
-:tloop	tax
-	sty tabs,x
-	sec
-	sbc #8
-	bne :tloop
-
 	rts
-*:table	db 8*1,8*2,8*3,8*4,8*5,8*6,8*7,8*8*,8*9
+:table	db 8*1,8*2,8*3,8*4,8*5,8*6,8*7,8*8*,8*9
 
 set_tab	ent
 * input x = x
@@ -58,8 +57,9 @@ next_tab_stop ent
 * input x = x
 
 *	ldx x
-	cpx 79
-	bge :80
+	inx
+	cpx #79
+	bge :79
 
 :loop	bit tabs,x
 	bmi :rts
@@ -68,7 +68,7 @@ next_tab_stop ent
 	bcc :loop
 
 
-:80	ldx	#80
+:79	ldx	#79
 :rts	rts
 
 
diff --git a/vt100.vt52.S b/vt100.vt52.S
index 1fd464e..d7687ab 100644
--- a/vt100.vt52.S
+++ b/vt100.vt52.S
@@ -1,16 +1,20 @@
-*
-* vt52 emulation for the vt100
-*
-* ESC < exits 
-
 	lst off
 
 	rel
 	xc
 	xc
-
 	use vt.equ
 
+	mx %11
+
+*
+* vt52 emulation for the vt100
+*
+* ESC < exits 
+
+
+
+
 	ext update_cursor,write_modem,draw_char
 
 
@@ -129,7 +133,9 @@ esc_D ; cursor left
 
 	lda x
 	beq :rts
-	dec x
+	and #$7f
+	dec
+	sta x
 	jmp update_cursor
 :rts	rts