allow clients to have same mon and tags than his parent

client.h

@@ -152,6 +152,35 @@ client_set_tiled(Client *c, uint32_t edges)
 			WLR_EDGE_BOTTOM | WLR_EDGE_LEFT | WLR_EDGE_RIGHT);
 }
 
+static inline pid_t
+client_get_pid(Client *c)
+{
+	pid_t pid;
+	if (client_is_x11(c))
+		pid = c->surface.xwayland->pid;
+	else
+		wl_client_get_credentials(c->surface.xdg->client->client, &pid, NULL, NULL);
+
+	return pid;
+}
+
+static inline Client *
+client_get_parent(Client *c)
+{
+	Client *p;
+	pid_t c_pid, p_pid;
+	if (!(c_pid = client_get_pid(c)))
+		return NULL;
+
+	wl_list_for_each(p, &clients, link) {
+		p_pid = client_get_pid(p);
+		if (c != p && p_pid && isdescprocess(p_pid, c_pid))
+			return p;
+	}
+
+	return NULL;
+}
+
 static inline struct wlr_surface *
 client_surface(Client *c)
 {

dwl.c

@@ -268,6 +268,8 @@ static void focusmon(const Arg *arg);
 static void focusstack(const Arg *arg);
 static void fullscreennotify(struct wl_listener *listener, void *data);
 static Client *focustop(Monitor *m);
+static pid_t getparentprocess(pid_t pid);
+static int isdescprocess(pid_t p, pid_t c);
 static int hidecursor(void *data);
 static int movecursor(void *data);
 static void incnmaster(const Arg *arg);
@@ -523,6 +525,7 @@ applyrules(Client *c)
 	const char *appid, *title;
 	unsigned int i, newtags = 0;
 	const Rule *r;
+	Client *p;
 	Monitor *mon = selmon, *m;
 
 	c->isfloating = client_is_float_type(c);
@@ -535,11 +538,16 @@ applyrules(Client *c)
 		if ((!r->title || strstr(title, r->title))
 				&& (!r->id || strstr(appid, r->id))) {
 			c->isfloating = r->isfloating;
-			newtags |= r->tags;
-			i = 0;
-			wl_list_for_each(m, &mons, link)
-				if (r->monitor == i++)
-					mon = m;
+			if ((p = client_get_parent(c))) {
+				newtags |= p->tags;
+				mon = p->mon;
+			} else {
+				newtags |= r->tags;
+				i = 0;
+				wl_list_for_each(m, &mons, link)
+					if (r->monitor == i++)
+						mon = m;
+			}
 		}
 	}
 	c->geom.x = (mon->w.width - c->geom.width) / 2;
@@ -1369,6 +1377,33 @@ focustop(Monitor *m)
 	return NULL;
 }
 
+pid_t
+getparentprocess(pid_t p)
+{
+	unsigned int v = 0;
+
+	FILE *f;
+	char buf[256];
+	snprintf(buf, sizeof(buf) - 1, "/proc/%u/stat", (unsigned)p);
+
+	if (!(f = fopen(buf, "r")))
+		return 0;
+
+	fscanf(f, "%*u %*s %*c %u", &v);
+	fclose(f);
+
+	return (pid_t)v;
+}
+
+int
+isdescprocess(pid_t p, pid_t c)
+{
+	while (p != c && c != 0)
+		c = getparentprocess(c);
+
+	return (int)c;
+}
+
 int
 movecursor(void *data)
 {