Change fullscreen policies

When a new client is spawned, fullscreen isn't disabled for all clients
in that monitor any more.

Instead, all fullscreen clients are kept fullscreen, while other clients
spawn in the background.

When fullscreen is disabled, all clients are rearranged.

This is made to make dwl more flexible allowing multiple fullscreen
clients at the same time, have floating clients on top of a fullscreen
one and let stuff happen without quitting fullscreen, like many other
WMs and DEs.

dwl.c

@@ -152,6 +152,7 @@ struct Monitor {
 	unsigned int tagset[2];
 	double mfact;
 	int nmaster;
+	Client *fullscreenclient;
 };
 
 typedef struct {
@@ -212,6 +213,7 @@ static void keypress(struct wl_listener *listener, void *data);
 static void keypressmod(struct wl_listener *listener, void *data);
 static void killclient(const Arg *arg);
 static void maprequest(struct wl_listener *listener, void *data);
+static void maximizeclient(Client *c);
 static void monocle(Monitor *m);
 static void motionabsolute(struct wl_listener *listener, void *data);
 static void motionnotify(uint32_t time);
@@ -220,7 +222,6 @@ static void moveresize(const Arg *arg);
 static void pointerfocus(Client *c, struct wlr_surface *surface,
 		double sx, double sy, uint32_t time);
 static void quit(const Arg *arg);
-static void quitallfullscreen();
 static void render(struct wlr_surface *surface, int sx, int sy, void *data);
 static void renderclients(Monitor *m, struct timespec *now);
 static void rendermon(struct wl_listener *listener, void *data);
@@ -380,6 +381,8 @@ arrange(Monitor *m)
 	m->w = m->m;
 	if (m->lt[m->sellt]->arrange)
 		m->lt[m->sellt]->arrange(m);
+	else if (m->fullscreenclient)
+		maximizeclient(m->fullscreenclient);
 	/* XXX recheck pointer focus here... or in resize()? */
 }
 
@@ -589,7 +592,6 @@ createnotify(struct wl_listener *listener, void *data)
 
 	if (xdg_surface->role != WLR_XDG_SURFACE_ROLE_TOPLEVEL)
 		return;
-	quitallfullscreen();
 
 	/* Allocate a Client for this surface */
 	c = xdg_surface->data = calloc(1, sizeof(*c));
@@ -687,17 +689,16 @@ togglefullscreen(const Arg *arg)
 }
 
 void
-quitallfullscreen()
+maximizeclient(Client *c)
 {
-	Client *c;
-	wl_list_for_each(c, &clients, link)
-		if (c->isfullscreen && VISIBLEON(c, selmon))
-			setfullscreen(c, 0);
+	resize(c, c->mon->m.x, c->mon->m.y, c->mon->m.width, c->mon->m.height, 0);
+	/* used for fullscreen clients */
 }
 
 void
 setfullscreen(Client *c, int fullscreen)
 {
+	c->isfullscreen = fullscreen;
 	c->bw = (1 - fullscreen) * borderpx;
 
 #ifdef XWAYLAND
@@ -707,18 +708,20 @@ setfullscreen(Client *c, int fullscreen)
 #endif
 		wlr_xdg_toplevel_set_fullscreen(c->surface.xdg, fullscreen);
 
-	// restore previous size instead of arrange to work with floating windows
 	if (fullscreen) {
-		quitallfullscreen();
 		c->prevx = c->geom.x;
 		c->prevy = c->geom.y;
 		c->prevheight = c->geom.height;
 		c->prevwidth = c->geom.width;
-		resize(c, c->mon->m.x, c->mon->m.y, c->mon->m.width, c->mon->m.height, 0);
+		c->mon->fullscreenclient = c;
+		maximizeclient(c);
 	} else {
+		/* restore previous size instead of arrange for floating windows since
+		 * client positions are set by the user and cannot be recalculated */
 		resize(c, c->prevx, c->prevy, c->prevwidth, c->prevheight, 0);
+		c->mon->fullscreenclient = NULL;
+		arrange(c->mon);
 	}
-	c->isfullscreen = fullscreen;
 }
 
 void
@@ -969,7 +972,7 @@ void
 maprequest(struct wl_listener *listener, void *data)
 {
 	/* Called when the surface is mapped, or ready to display on-screen. */
-	Client *c = wl_container_of(listener, c, map);
+	Client *c = wl_container_of(listener, c, map), *oldfocus = selclient();
 
 #ifdef XWAYLAND
 	if (c->type == X11Unmanaged) {
@@ -1000,6 +1003,14 @@ maprequest(struct wl_listener *listener, void *data)
 
 	/* Set initial monitor, tags, floating status, and focus */
 	applyrules(c);
+
+	if (c->mon->fullscreenclient && c->mon->fullscreenclient == oldfocus
+			&& !c->isfloating && c->mon->lt[c->mon->sellt]->arrange) {
+		maximizeclient(c->mon->fullscreenclient);
+		focusclient(c, c->mon->fullscreenclient, 1);
+		/* give the focus back the fullscreen client on that monitor if exists,
+		 * is focused and the new client isn't floating */
+	}
 }
 
 void
@@ -1010,11 +1021,10 @@ monocle(Monitor *m)
 	wl_list_for_each(c, &clients, link) {
 		if (!VISIBLEON(c, m) || c->isfloating)
 			continue;
-		if (c->isfullscreen) {
-			resize(c, c->mon->m.x, c->mon->m.y, c->mon->m.width, c->mon->m.height, 0);
-			return;
-		}
-		resize(c, m->w.x, m->w.y, m->w.width, m->w.height, 0);
+		if (c->isfullscreen)
+			maximizeclient(c);
+		else
+			resize(c, m->w.x, m->w.y, m->w.width, m->w.height, 0);
 	}
 }
 
@@ -1452,8 +1462,6 @@ setcursor(struct wl_listener *listener, void *data)
 void
 setfloating(Client *c, int floating)
 {
-	if (c->isfloating == floating)
-		return;
 	c->isfloating = floating;
 	arrange(c->mon);
 }
@@ -1723,11 +1731,9 @@ tile(Monitor *m)
 	wl_list_for_each(c, &clients, link) {
 		if (!VISIBLEON(c, m) || c->isfloating)
 			continue;
-		if (c->isfullscreen) {
-			resize(c, c->mon->m.x, c->mon->m.y, c->mon->m.width, c->mon->m.height, 0);
-			return;
-		}
-		if (i < m->nmaster) {
+		if (c->isfullscreen)
+			maximizeclient(c);
+		else if (i < m->nmaster) {
 			h = (m->w.height - my) / (MIN(n, m->nmaster) - i);
 			resize(c, m->w.x, m->w.y + my, mw, h, 0);
 			my += c->geom.height;
@@ -1873,7 +1879,6 @@ createnotifyx11(struct wl_listener *listener, void *data)
 {
 	struct wlr_xwayland_surface *xwayland_surface = data;
 	Client *c;
-	quitallfullscreen();
 
 	/* Allocate a Client for this surface */
 	c = xwayland_surface->data = calloc(1, sizeof(*c));