From c26fdb09b16ce4b063ebd75b0af554c25d7735af Mon Sep 17 00:00:00 2001
From: Thomas Adam <thomas@fvwm.org>
Date: Sat, 25 Nov 2023 23:42:01 +0000
Subject: [PATCH] monitors: update 'number' field

Tag each monitor with a number when inserting -- the idea being that
monitor 0 -> n represents the ordering for each monitor.
---
 fvwm/expand.c  |  2 +-
 libs/FScreen.c | 44 ++++++++++++++++++++++++++++++++++++--------
 libs/FScreen.h |  2 +-
 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/fvwm/expand.c b/fvwm/expand.c
index e781e170f..866348f0e 100644
--- a/fvwm/expand.c
+++ b/fvwm/expand.c
@@ -560,7 +560,7 @@ static signed int expand_vars_extended(
 		while ((m_name = strsep(&rest_s, ".")) != NULL) {
 			if ((pos = atoi(m_name)) >= 0) {
 				RB_FOREACH(m_loop, monitors, &monitor_q) {
-					if (m_loop->si->number == pos) {
+					if (m_loop->number == pos) {
 						mon2 = m_loop;
 						break;
 					}
diff --git a/libs/FScreen.c b/libs/FScreen.c
index 190a2eb6c..5b6f2930c 100644
--- a/libs/FScreen.c
+++ b/libs/FScreen.c
@@ -49,6 +49,7 @@ static bool		 randr_initialised;
 static void		 scan_screens(Display *);
 static struct monitor	*monitor_by_name(const char *);
 static void		 monitor_set_coords(struct monitor *, XRRMonitorInfo);
+static void		 monitor_assign_number(void);
 
 enum monitor_tracking monitor_mode;
 bool			 is_tracking_shared;
@@ -382,7 +383,7 @@ monitor_output_change(Display *dpy, XRRScreenChangeNotifyEvent *e)
 		XRROutputInfo		*oinfo = NULL;
 		int			 i;
 
-		//scan_screens(dpy);
+		scan_screens(dpy);
 
 		for (i = 0; i < res->noutput; i++) {
 			oinfo = XRRGetOutputInfo(dpy, res, res->outputs[i]);
@@ -462,15 +463,37 @@ monitor_set_coords(struct monitor *m, XRRMonitorInfo rrm)
 	}
 }
 
+static void
+monitor_assign_number(void)
+{
+	struct monitor	*m;
+	int		 n = 0;
+
+	RB_FOREACH(m, monitors, &monitor_q) {
+		if (m->flags & MONITOR_DISABLED)
+			continue;
+		m->number = n++;
+	}
+}
+
 int
 monitor_compare(struct monitor *a, struct monitor *b)
 {
 	fvwm_debug(__func__, "a: %s, y: %d x: %d", a->si->name, a->si->y, a->si->x);
 	fvwm_debug(__func__, "b: %s, y: %d x: %d", b->si->name, b->si->y, b->si->x);
 
-	if (a->si->y == b->si->y)
-		return a->si->x - b->si->x;
-	return b->si->y - a->si->y;
+	/* XXX: Optimise. */
+	if (a->si->y < b->si->y)
+		return -1;
+	else if (a->si->y > b->si->y)
+		return 1;
+	else {
+		if (a->si->x < b->si->x)
+			return -1;
+		else if (a->si->x > b->si->x)
+			return 1;
+	}
+	return 0;
 }
 
 static void
@@ -486,8 +509,6 @@ scan_screens(Display *dpy)
 		exit(101);
 	}
 
-	fvwm_debug(__func__, "HERE: 1 (%d)", n);
-
 	for (i = 0; i < n; i++) {
 		struct monitor 	*m = NULL;
 		char		*name = XGetAtomName(dpy, rrm[i].name);
@@ -510,10 +531,11 @@ scan_screens(Display *dpy)
 			m->virtual_scr.edge_thickness = 2;
 			m->virtual_scr.last_edge_thickness = 2;
 
-			fvwm_debug(__func__, "HERE: 3");
 			monitor_set_coords(m, rrm[i]);
 			TAILQ_INSERT_TAIL(&screen_info_q, m->si, entry);
 			RB_INSERT(monitors, &monitor_q, m);
+
+			goto done;
 		}
 
 		RB_FOREACH(m, monitors, &monitor_q) {
@@ -526,10 +548,16 @@ scan_screens(Display *dpy)
 				monitor_set_coords(m, rrm[i]);
 			}
 		}
+done:
 		if (name != NULL)
 			XFree(name);
 	}
 
+
+	/* Now that all monitors have been inserted, assign them a number from
+	 * 0 -> n so that they can be referenced in order.
+	 */
+	monitor_assign_number();
 	monitor_check_primary();
 	XRRFreeMonitors(rrm);
 }
@@ -644,7 +672,7 @@ monitor_dump_state(struct monitor *m)
 			"\t\tMyDisplayWidth: %d, MyDisplayHeight: %d\n\t}\n"
 			"\tDesktops:\t%s\n"
 			"\tFlags:%s\n\n",
-			m2->si->number,
+			m2->number,
 			m2->si->name,
 			(m2->flags & MONITOR_DISABLED) ? "true" : "false",
 			(m2->flags & MONITOR_PRIMARY) ? "yes" : "no",
diff --git a/libs/FScreen.h b/libs/FScreen.h
index ac0f06e8e..aec9dd963 100644
--- a/libs/FScreen.h
+++ b/libs/FScreen.h
@@ -58,7 +58,6 @@ extern bool is_tracking_shared;
 struct screen_info {
 	const char		*name;
 	int			 x, y, w, h;
-	int			 number;
 	RROutput		 rr_output;
 
 	TAILQ_ENTRY(screen_info) entry;
@@ -84,6 +83,7 @@ struct monitor {
 	struct screen_info	*si;
 	int			 flags;
 	int			 emit;
+	int			 number;
 	int			 dx, dy;
 	bool			 is_prev, was_primary;