From 6521e971cdb772c53256d84a54c8d7b2d1ffa632 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Sun, 1 Mar 2026 02:00:23 -0500
Subject: Scrollback!

---
 Makefile       |   4 +-
 font_dl.asm    | 117 ++++++++++++++++++++++++++++++++++-----------------------
 memsetup.asm   |   2 +-
 size.pl        |   6 +--
 src/addrs.c    |  67 +++++++++++++++++++++++----------
 src/addrs.h    |  32 ++++++++++++----
 src/atari.cfg  |   4 +-
 src/edbox.c    |  16 ++++++--
 src/keyclick.h |   1 +
 src/keyclick.s |  53 ++++++++++++++++++++++++++
 src/main.c     |   3 +-
 src/screen.c   |  50 ++++++++++++++++++------
 src/screen.h   |  16 ++++++--
 uitest/test.c  |   6 ++-
 14 files changed, 273 insertions(+), 104 deletions(-)
 create mode 100644 src/keyclick.h
 create mode 100644 src/keyclick.s

diff --git a/Makefile b/Makefile
index e48f3c3..7b8aa9a 100644
--- a/Makefile
+++ b/Makefile
@@ -24,6 +24,6 @@ memsetup.xex: memsetup.asm
 
 font_dl.xex: font_dl.asm font.dat
 
-test:
-	cl65 -C src/atari.cfg -t atari -o testmain.xex src/addrs.c src/edbox.c src/screen.c uitest/test.c
+test: memsetup.xex font_dl.xex
+	cl65 -C src/atari.cfg -t atari -o testmain.xex src/addrs.c src/edbox.c src/screen.c src/keyclick.s uitest/test.c
 	cat memsetup.xex font_dl.xex testmain.xex > test.xex
diff --git a/font_dl.asm b/font_dl.asm
index bbb2b98..28599e8 100644
--- a/font_dl.asm
+++ b/font_dl.asm
@@ -1,56 +1,77 @@
- *= $a000
+
+ *= $8000
  .incbin "font.dat"
-dlist
+
+; screen RAM starts right after the font.
+; 7 double-height screens, 50 lines each.
+scr0_top
+ *= * + 1000
+scr1_top
+ *= * + 1000
+scr2_top
+ *= * + 1000
+
+; can't cross a 4K boundary...
+ *= $9000
+scr3_top
+ *= * + 1000
+scr4_top
+ *= * + 1000
+scr5_top
+ *= * + 1000
+scr6_top
+
+; shoehorn the transmit & receive buffers here
+ *= $a000
+rx_buf ; 512 bytes
+ *= $a200
+tx_buf ; 512 bytes
+ *= $a400
+
+scr0_bot
+ *= * + 1000
+scr1_bot
+ *= * + 1000
+scr2_bot
+ *= * + 1000
+
+ *= $b000
+scr3_bot
+ *= * + 1000
+scr4_bot
+ *= * + 1000
+scr5_bot
+ *= * + 1000
+scr6_bot
+
+ *= * + 1000
+dlist_top
+ *= * + 48
+dlist_bot
+ *= * + 48
+
+ *= dlist_top ; used when scrolled up
  .byte $70, $70, $30 ; 2 8-line blanks, 1 4-line blank
  .byte $42           ; LMS GR.0
 dl_top_lms
- .word $a500         ; base address of 1st screen
+ .word scr0_top
+ .byte $02, $02, $02, $02, $02, $02, $02, $02
+ .byte $02, $02, $02, $02, $02, $02, $02, $02
+ .byte $02, $02, $02, $02, $02, $02, $02, $02 ; 24 GR.0 lines
+ .byte $41           ; JVB
+ .word dlist_top
+
+ *= dlist_bot ; used when not scrolled up
+ .byte $70, $70, $30 ; 2 8-line blanks, 1 4-line blank
+ .byte $42           ; LMS GR.0
+dl_bot_lms
+ .word scr0_bot
  .byte $02, $02, $02, $02, $02, $02, $02, $02
  .byte $02, $02, $02, $02, $02, $02, $02, $02
  .byte $02, $02, $02, $02, $02, $02 ; 22 GR.0 lines
- .byte $00           ; 1 blank line
- .byte $42           ; another LMS (edit/status box)
-dl_bottom_lms
- .word $a480         ; edit box base address
- .word $02           ; 2nd line of edit box
+ .byte $42           ; LMS GR.0
+dl_status_lms
+ .word scr0_bot+920 ; line 23
  .byte $41           ; JVB
- .word dlist
-
-status_box
- *= * + 80 ; 2 lines
-
-edit_box
- *= * + 160 ; 4 lines
-
-end_boxes ; currently $a515
-
-; screens are 920 bytes each (23 lines * 40), cannot
-; cross the 4K boundary at $b000, and must end 
-; before the ROM (or unwired addresses) at $c000.
-
-; on a 52K machine (expanded 800 or XL/XE running Translator),
-; we'd have another 4K of RAM from $c000-$cfff. With Translator,
-; we also could have 2K at $d800-$dfff (the floating point ROM,
-; which we don't use)... and we wouldn't have to have the font
-; at $a000, it could be plopped right into the OS default location
-; at $e000. maybe this will happen someday. meanwhile:
-
- *= $b000 - (920 * 3)
-screen0
- *= * + 920
-screen1
- *= * + 920
-screen2      ; ends 1 byte before $b000 boundary
- *= * + 920
-screen3      ; starts at $b000 boundary
- *= * + 920
-screen4
- *= * + 920
-screen5
- *= * + 920
-screen6
- *= * + 920
-end_screens ; currently $be60
-
-; 7 screens ain't so bad, really. eventually though, we want to
-; add scrollback to them, meaning fewer of them. sigh.
+ .word dlist_bot
+
diff --git a/memsetup.asm b/memsetup.asm
index 49d8149..3fe19d1 100644
--- a/memsetup.asm
+++ b/memsetup.asm
@@ -1,6 +1,6 @@
  *= $2000
 memsetup
- lda #$a0
+ lda #$80
  sta $6a    ; RAMTOP
  sta $02e6  ; MEMTOP high
  lda #0
diff --git a/size.pl b/size.pl
index f6cb19f..c38c274 100644
--- a/size.pl
+++ b/size.pl
@@ -1,11 +1,11 @@
 #!/usr/bin/perl -w
 
 # from src/atari.cfg:
-my $code_start = 0x2000;
-my $stack_size = 0x0800;
+my $code_start = 0x0700;
+my $stack_size = 0x0100;
 
 # from memsetup.asm:
-my $ramtop = 0xa000;
+my $ramtop = 0x8000;
 
 open MAP, "client.xex.map" or die $!;
 while(<MAP>) {
diff --git a/src/addrs.c b/src/addrs.c
index 8c4ad1b..5154109 100644
--- a/src/addrs.c
+++ b/src/addrs.c
@@ -1,27 +1,56 @@
 #include "addrs.h"
 
-u8 *dlist = u8p(DLIST_ADDR);
-u16 *dlist_top_lms = u16p(0xa404);
-u16 *dlist_bottom_lms = u16p(0xa41e);
-u8 *status_box = u8p(0xa425); /* 80 bytes */
-u8 *edit_box = u8p(0xa475); /* 160 bytes */
+u8 *dlist_top = u8p(DLIST_TOP_ADDR);
+u8 *dlist_bot = u8p(DLIST_BOT_ADDR);
 
-u8 *screen_addrs[7] = {
-	u8p(0xa538),
-	u8p(0xa8d0),
-	u8p(0xac68),
+u16 *dlist_top_lms = u16p(0xbfa4);
+u16 *dlist_bot_lms = u16p(0xbfd4);
+u16 *dlist_status_lms = u16p(0xbfed);
+
+u8 *edit_box = u8p(0x0600); /* up to 256 bytes (page 6) */
+u8 *rx_buf = u8p(0xa000); /* 512 bytes */
+u8 *tx_buf = u8p(0xa200); /* 512 bytes */
+
+/* 1000 bytes (25 40-char lines) apiece. */
+u8 *screen_top_addrs[7] = {
+	u8p(0x8400),
+	u8p(0x87e8),
+	u8p(0x8bd0),
+	u8p(0x9000),
+	u8p(0x93e8),
+	u8p(0x97d0),
+	u8p(0x9bb8)
+};
+
+/* 1000 bytes (25 40-char lines) apiece. */
+u8 *screen_bot_addrs[7] = {
+	u8p(0xa400),
+	u8p(0xa7e8),
+	u8p(0xabd0),
 	u8p(0xb000),
-	u8p(0xb398),
-	u8p(0xb730),
-	u8p(0xbac8)
+	u8p(0xb3e8),
+	u8p(0xb7d0),
+	u8p(0xbbb8)
 };
 
-u8 *screen_botlines[7] = {
-	u8p(0xa8a8),
-	u8p(0xac40),
-	u8p(0xafd8),
+/* 40 bytes (1 line), third from the bottom of each _bot_addr */
+u8 *screen_lastlines[7] = {
+	u8p(0xa770),
+	u8p(0xab58),
+	u8p(0xaf40),
 	u8p(0xb370),
-	u8p(0xb708),
-	u8p(0xbaa0),
-	u8p(0xbe38)
+	u8p(0xb758),
+	u8p(0xbb40),
+	u8p(0xbf28)
+};
+
+/* 80 bytes (2 lines), bottom 2 of each _bot_addr */
+u8 *status_boxes[7] = {
+	u8p(0xa798),
+	u8p(0xab80),
+	u8p(0xaf68),
+	u8p(0xb398),
+	u8p(0xb780),
+	u8p(0xbb68),
+	u8p(0xbf50)
 };
diff --git a/src/addrs.h b/src/addrs.h
index 6d44a68..dd9f23d 100644
--- a/src/addrs.h
+++ b/src/addrs.h
@@ -1,15 +1,33 @@
-#define FONT_ADDR_HI 0xa0
-#define DLIST_ADDR 0xa400
+#define FONT_ADDR_HI 0x80
+#define DLIST_TOP_ADDR 0xbfa0
+#define DLIST_BOT_ADDR 0xbfd0
 
 #define u8 unsigned char
 #define u8p(x) ((unsigned char *)x)
 #define u16 unsigned int
 #define u16p(x) ((unsigned int *)x)
 
-extern u8 *dlist;
+/* dlist_bot is the main one, dlist_top is used when
+   scrolled back. */
+extern u8 *dlist_top, *dlist_bot;
+
 extern u16 *dlist_top_lms;
-extern u16 *dlist_bottom_lms;
-extern u8 *status_box;
+extern u16 *dlist_bot_lms;
+
+/* points to either edit_box or one of the status_boxes[] */
+extern u16 *dlist_status_lms;
+
+/* only one of these (not one per screen) */
 extern u8 *edit_box;
-extern u8 *screen_addrs[7];
-extern u8 *screen_botlines[7];
+
+/* used for scrollback */
+extern u8 *screen_top_addrs[7];
+
+/* normal (non-scrollback) display */
+extern u8 *screen_bot_addrs[7];
+
+/* address of last line of _bot, where printing actually happens */
+extern u8 *screen_lastlines[7];
+
+/* bottom 2 lines of the _bot display list for each screen */
+extern u8 *status_boxes[7];
diff --git a/src/atari.cfg b/src/atari.cfg
index ea190f7..97b265e 100644
--- a/src/atari.cfg
+++ b/src/atari.cfg
@@ -1,5 +1,5 @@
 FEATURES {
-    STARTADDRESS: default = $2000;
+    STARTADDRESS: default = $0700;
 }
 SYMBOLS {
     __EXEHDR__:          type = import;
@@ -16,7 +16,7 @@ MEMORY {
 
 # "main program" load chunk
     MAINHDR:    file = %O,               start = $0000, size = $0004;
-    MAIN:       file = %O, define = yes, start = %S,    size = $BC20 - __STACKSIZE__ - __RESERVED_MEMORY__ - %S;
+    MAIN:       file = %O, define = yes, start = %S,    size = $8000 - __STACKSIZE__ - __RESERVED_MEMORY__ - %S;
     TRAILER:    file = %O,               start = $0000, size = $0006;
 }
 SEGMENTS {
diff --git a/src/edbox.c b/src/edbox.c
index 9231b50..0903cb9 100644
--- a/src/edbox.c
+++ b/src/edbox.c
@@ -4,6 +4,7 @@
 #include "addrs.h"
 #include "screen.h"
 #include "edbox.h"
+#include "keyclick.h"
 
 /* TODO: tab completion */
 
@@ -37,7 +38,7 @@ void edbox_show(void) {
 
 	scr_waitvcount(116);
 
-	*dlist_bottom_lms = addr;
+	*dlist_status_lms = addr;
 	show_cursor();
 }
 
@@ -96,6 +97,7 @@ void edbox_readline(char *dest, char len) {
 }
 
 static void special_keystroke(char c) {
+	keyclick();
 	OS.ch = 0xff;
 	edbox_putc(c);
 }
@@ -178,11 +180,9 @@ void edbox_keystroke(void) {
 		;
 
 	edbox_show();
-	hide_cursor();
 
-	OS.invflg = c = 0;
+	c = 0;
 
-	/* XXX: these keys don't click. */
 	switch(OS.ch) {
 		case 0xa0:       /* key: ctrl [ */
 			c = 0x7b;     /* ascii: { */
@@ -197,6 +197,12 @@ void edbox_keystroke(void) {
 		case 0x9c:       /* key: ctrl ESC */
 			c = 0x7e;     /* ascii: ~ */
 			break;
+		case 0x3c:       /* caps */
+			OS.shflok ^= 0x40;
+			keyclick();
+			break;
+		case 0x7c:       /* shift-caps */
+		case 0xbc:       /* ctrl-caps */
 		case 0x27:       /* atari key */
 		case 0x67:       /* ...w/shift */
 		case 0x97:       /* ...w/ctrl */
@@ -207,6 +213,8 @@ void edbox_keystroke(void) {
 			break;
 	}
 
+	hide_cursor();
+
 	if(c) {
 		special_keystroke(c);
 	} else {
diff --git a/src/keyclick.h b/src/keyclick.h
new file mode 100644
index 0000000..b73a212
--- /dev/null
+++ b/src/keyclick.h
@@ -0,0 +1 @@
+extern void keyclick(void);
diff --git a/src/keyclick.s b/src/keyclick.s
new file mode 100644
index 0000000..bbe613c
--- /dev/null
+++ b/src/keyclick.s
@@ -0,0 +1,53 @@
+ .include "atari.inc"
+ .export _keyclick
+
+; keyclick.s - just what you think it is.
+
+; How do you make it possible to disable the keyclick on the 400/800?
+; Don't use the OS K: handler.
+
+ ;.ifdef REAL_KEYCLICK
+ .if 1
+
+; Copied from OS ROM source, 12 bytes of code. Because of the repeated
+; stx WSYNC, you don't want to use this if you're using DLIs.
+; Preserves A and Y, returns with X=$ff, N set, Z clear.
+_keyclick:
+ ldx #$7f
+@rc1:
+ stx CONSOL
+ stx WSYNC
+ dex
+ bpl @rc1
+ rts
+
+ .else
+
+; Fake keyclick. 25 bytes of code. Sounds just like the real one, but
+; it won't mess up your DLIs because it's interruptible (though DLIs
+; might mess it up). Loop timing assumes a GR.0 type display list
+; with playfield DMA enabled and P/M DMA disabled.
+; Preserves A, returns with X=$ff, Y=0, N set, Z clear.
+_keyclick:
+@wcount:
+ ldx VCOUNT   ; To make the timing consistent, wait until we're sure
+ cpx #$10     ; that ANTIC is doing DMA.
+ bne @wcount
+
+ ldx #$7f
+@click:     ; I tuned this by ear, then cycle-counted afterward.
+ stx CONSOL ; 4
+ ldy #$07   ; 2
+ ;lda #0     ; 2
+ nop
+@c1:
+ dey        ; inner: 2
+ nop        ;        2
+ bne @c1    ;        3
+            ;        7 cycles/loop, *7 = 49, -1 for failed BNE
+			   ; 48
+ dex        ; 2
+ bpl @click ; 3 = 61
+ rts
+
+ .endif
diff --git a/src/main.c b/src/main.c
index be40d95..2685da8 100644
--- a/src/main.c
+++ b/src/main.c
@@ -29,8 +29,7 @@ unsigned char trip=0;           // if trip=1, fujinet is asking us for attention
 bool old_enabled=false;         // were interrupts enabled for old vector
 void* old_vprced;               // old PROCEED vector, restored on exit.
 unsigned short bw=0;            // # of bytes waiting.
-unsigned char rx_buf[MAX_IRC_MSG_LEN];      // RX buffer.
-unsigned char tx_buf[MAX_IRC_MSG_LEN];      // TX buffer.
+extern char *rx_buf, *tx_buf /* 512 bytes each, see addrs.c */
 unsigned int txbuflen;         // TX buffer length
 char channel[32] = DEF_CHANNEL;
 
diff --git a/src/screen.c b/src/screen.c
index b98a26a..252d39d 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -25,14 +25,17 @@ void scr_waitvcount(u8 c) {
 }
 
 static void scr_clear(char s) {
-	memset(screen_addrs[s], 0, SCREEN_SIZE);
+	memset(screen_top_addrs[s], 0, 1000);
+	memset(screen_bot_addrs[s], 0, 1000);
 	memset(scr_names[s], 0, 32);
 	memset(scr_topics[s], 0, LINE_SIZE);
 }
 
 static void scr_scroll(char s) {
-	memmove(screen_addrs[s], screen_addrs[s] + 40, 880);
-	memset(screen_botlines[s], 0, 40);
+	memmove(screen_top_addrs[s], screen_top_addrs[s] + 40, 960);
+	memmove(screen_top_addrs[s] + 960, screen_bot_addrs[s], 40);
+	memmove(screen_bot_addrs[s], screen_bot_addrs[s] + 40, 920);
+	memset(screen_lastlines[s], 0, 40);
 }
 
 void scr_init(void) {
@@ -41,7 +44,7 @@ void scr_init(void) {
 	old_dma = OS.sdmctl;
 	OS.sdmctl = 0;
 	scr_waitvcount(112); /* after the last GR.0 line */
-	*SDLST = DLIST_ADDR;
+	*SDLST = DLIST_BOT_ADDR;
 	OS.chbas = FONT_ADDR_HI;
 
 	for(i = 0; i < MAX_SCREENS; i++) {
@@ -106,21 +109,36 @@ void scr_display(char s) {
 	scr_current = s;
 
 	scr_waitvcount(112);
-	*dlist_top_lms = (u16)screen_addrs[s];
+	*dlist_bot_lms = (u16)screen_bot_addrs[s];
 
 	scr_show_status(s);
 }
 
+void scr_scrollback(void) {
+	// OS.color2 = 0;
+	scr_waitvcount(112);
+	*dlist_top_lms = (u16)screen_top_addrs[scr_current];
+	*SDLST = (u16)dlist_top;
+}
+
+void scr_end_scrollback(void) {
+	// OS.color2 = 192;
+	scr_waitvcount(112);
+	*SDLST = (u16)dlist_bot;
+}
+
 void scr_show_status(char s) {
 	int i;
 	char *p, sc;
 
-	status_box[0] = s + 177; /* inverse number */
-	status_box[1] = ':';
-	strncpy(status_box + 2, scr_names[s], 32);
-	strncpy(status_box + 40, scr_topics[s], 40);
+	/* this part should be moved to _create() */
+	p = status_boxes[s];
+	p[0] = s + 177; /* inverse number */
+	p[1] = ':';
+	strncpy(p + 2, scr_names[s], 32);
+	strncpy(p + 40, scr_topics[s], 40);
 
-	p = status_box + 33;
+	p += 33;
 	for(i = 0; i < MAX_SCREENS; i++) {
 		switch(scr_status[i]) {
 			case SCR_ACTIVE:
@@ -134,7 +152,7 @@ void scr_show_status(char s) {
 	}
 
 	scr_waitvcount(112);
-	*dlist_bottom_lms = (u16)status_box;
+	*dlist_status_lms = (u16)status_boxes[s];
 }
 
 void scr_refresh(void) {
@@ -152,6 +170,14 @@ char scr_getbyname(const char *name) {
 	return 0;
 }
 
+void scr_putc_active(char c) {
+	scr_putc(scr_active, c);
+}
+
+void scr_eol_active(void) {
+	scr_putc(scr_active, '\n');
+}
+
 /* TODO: skip color codes (start with 0x03 or 0x04).
    if we're going to ever support utf-8, decode it here...
    also, 0x16 is supposed to be reverse video. not widely used/supported.
@@ -176,7 +202,7 @@ void scr_putc(char s, char c) {
 		xpos = 0;
 	}
 
-	dest = screen_botlines[s] + xpos;
+	dest = screen_lastlines[s] + xpos;
 
 	if(c & 0x80) {
 		/* utf-8 (or maybe latin-1), we don't support it yet */
diff --git a/src/screen.h b/src/screen.h
index fe8c928..bb70999 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -33,9 +33,9 @@ extern char scr_status[MAX_SCREENS];
 void scr_init(void);
 
 /* creates a screen, if possible. we only get 7; attempts to create
-   more that that will return -1. on success, returns the screen
-   number (0-6). the name gets copied to the 1st line of the screen's
-   status box.
+   more that that will return 0 (aka the server screen). on success,
+   returns the screen number (2-6). the name gets copied to the 1st
+   line of the screen's status box.
 	if display is true, the new screen displays. otherwise it's created
    "in the background".
  */
@@ -54,6 +54,14 @@ void scr_set_topic(char s, const char *topic);
    s's active flag. calls scr_show_status(). */
 void scr_display(char s);
 
+/* display the backscroll (top 25 lines) of the current screen.
+   note that it's a bad idea to write to the screen while it's
+   scrolled back!  */
+void scr_scrollback(void);
+
+/* end scrollback mode (display the bottom 23 lines + status) */
+void scr_end_scrollback(void);
+
 /* XXX: does this need to be public? */
 void scr_show_status(char s);
 
@@ -71,6 +79,8 @@ void scr_activate_name(const char *name);
 /* print one character to a screen. handles scrolling. will not
    print an EOL at column 0 (just ignores it). */
 void scr_putc(char s, char c);
+void scr_putc_active(char c);
+void scr_eol_active(void);
 
 /* print text to a screen. handles scrolling. this
    doesn't have to be the screen being displayed, of course;
diff --git a/uitest/test.c b/uitest/test.c
index 3cd3fc5..a3ae1a9 100644
--- a/uitest/test.c
+++ b/uitest/test.c
@@ -47,7 +47,11 @@ int main() {
 		if(OS.ch != 0xff) {
 			if(GTIA_READ.consol == 6) { /* start pressed */
 				i = cgetc();
-				if(i >= '1' && i <= '7') {
+				if(i == 's') {
+					scr_scrollback();
+					cgetc();
+					scr_end_scrollback();
+				} else if(i >= '1' && i <= '7') {
 					if(scr_status[i - '1'] != SCR_UNUSED)
 						scr_display(i - '1');
 				} else if(i == 'n') {
-- 
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