FvwmEvent: flip prev_focused monitor

When handling focus between screens (which is predicated on windows
receiving focus, rather than the root window), toggle the appropriate
monitors so that the previous focused monitor is referenced correctly.

While here, improve the matching of the previous monitor.

Fixes #604

fvwm/events.c

@@ -182,6 +182,8 @@ typedef struct
 } _merge_cr_args;
 
 /* ---------------------------- forward declarations ----------------------- */
+static void toggle_prev_monitor_state(struct monitor *, struct monitor *,
+    FvwmWindow *);
 
 /* ---------------------------- local variables ---------------------------- */
 
@@ -1981,6 +1983,35 @@ void HandleDestroyNotify(const evh_args_t *ea)
 	return;
 }
 
+static void
+toggle_prev_monitor_state(struct monitor *this, struct monitor *prev,
+    FvwmWindow *fw)
+{
+	if (fw == NULL) {
+		/* Assume root window. */
+		if (this != prev) {
+			BroadcastName(MX_MONITOR_FOCUS, -1, -1, -1,
+			    this->si->name /* Name of the monitor. */
+			);
+		}
+		/* Toggle the state of the previous monitor. */
+		prev->is_prev = false;
+		this->is_prev = true;
+
+		return;
+	}
+
+	if (fw->m != prev) {
+		BroadcastName(MX_MONITOR_FOCUS, -1, -1, -1,
+			this->si->name /* Name of the monitor. */
+		);
+
+		/* Toggle the state of the previous monitor. */
+		prev->is_prev = false;
+		this->is_prev = true;
+	}
+}
+
 #if DEBUG_ENTERNOTIFY
 static int ecount=0;
 #define ENTER_DBG(x) fprintf x;
@@ -2223,6 +2254,14 @@ void HandleEnterNotify(const evh_args_t *ea)
 			InstallWindowColormaps(NULL);
 		}
 		focus_grab_buttons(lf);
+
+		struct monitor *pfm, *this_m;
+		pfm = monitor_resolve_name(prev_focused_monitor);
+		this_m = monitor_get_current();
+
+		/* Send MX_MONITOR_FOCUS event. */
+		toggle_prev_monitor_state(this_m, pfm, NULL);
+
 		return;
 	}
 	else
@@ -2312,9 +2351,20 @@ void HandleEnterNotify(const evh_args_t *ea)
 	    ewp->window == FW_W_ICON_TITLE(fw) ||
 	    ewp->window == FW_W_ICON_PIXMAP(fw))
 	{
-		BroadcastPacket(
-			MX_ENTER_WINDOW, 3, (long)FW_W(fw),
-			(long)FW_W_FRAME(fw), (unsigned long)fw);
+		struct monitor *pfm;
+		pfm = monitor_resolve_name(prev_focused_monitor);
+
+		BroadcastPacket(MX_ENTER_WINDOW, 3, (long)FW_W(fw),
+		    (long)FW_W_FRAME(fw), (unsigned long)fw);
+
+		if (fw != NULL) {
+			/* Send MX_MONITOR_FOCUS event. */
+			toggle_prev_monitor_state(fw->m, pfm, fw);
+
+			if (pfm->virtual_scr.CurrentDesk !=
+			    fw->m->virtual_scr.CurrentDesk)
+				EWMH_SetCurrentDesktop(fw->m);
+		}
 	}
 	sf = get_focus_window();
 	if (sf && fw != sf && FP_DO_UNFOCUS_LEAVE(FW_FOCUS_POLICY(sf)))
@@ -2577,20 +2627,6 @@ void HandleFocusIn(const evh_args_t *ea)
 				(unsigned long)IsLastFocusSetByMouse(),
 				(long)fc, (long)bc);
 			EWMH_SetActiveWindow(focus_w);
-
-			struct monitor *pfm;
-			pfm = monitor_resolve_name(prev_focused_monitor);
-
-			if (fw != NULL && fw->m != pfm) {
-				pfm->is_prev = true;
-				fw->m->is_prev = false;
-				BroadcastName(MX_MONITOR_FOCUS, -1, -1, -1,
-				    fw->m->si->name /* Name of the monitor. */
-			        );
-				if (pfm->virtual_scr.CurrentDesk !=
-				    fw->m->virtual_scr.CurrentDesk)
-					EWMH_SetCurrentDesktop(fw->m);
-			}
 		}
 		last_focus_w = focus_w;
 		last_focus_fw = focus_fw;

libs/FScreen.c

@@ -167,8 +167,11 @@ struct monitor *
 monitor_get_prev(void)
 {
 	struct monitor	*m, *mret = NULL;
+	struct monitor  *this = monitor_get_current();
 
 	TAILQ_FOREACH(m, &monitor_q, entry) {
+		if (m == this)
+			continue;
 		if (m->is_prev) {
 			mret = m;
 			break;
@@ -537,6 +540,7 @@ void FScreenInit(Display *dpy)
 		m->Desktops->next = NULL;
 		m->Desktops->desk = 0;
 		m->flags |= (MONITOR_NEW|MONITOR_ENABLED);
+		m->is_prev = false;
 		monitor_scan_edges(m);
 	}
 
@@ -572,6 +576,7 @@ monitor_dump_state(struct monitor *m)
 			"\tDisabled:\t%s\n"
 			"\tIs Primary:\t%s\n"
 			"\tIs Current:\t%s\n"
+			"\tIs Previous:\t%s\n"
 			"\tOutput:\t%d\n"
 			"\tCoords:\t{x: %d, y: %d, w: %d, h: %d}\n"
 			"\tVirtScr: {\n"
@@ -586,6 +591,7 @@ monitor_dump_state(struct monitor *m)
 			(m2->flags & MONITOR_DISABLED) ? "true" : "false",
 			(m2->flags & MONITOR_PRIMARY) ? "yes" : "no",
 			(mcur && m2 == mcur) ? "yes" : "no",
+			m2->is_prev ? "yes" : "no",
 			(int)m2->si->rr_output,
 			m2->si->x, m2->si->y, m2->si->w, m2->si->h,
 			m2->virtual_scr.VxMax, m2->virtual_scr.VyMax,