patch: swallow

This patch adds "window swallowing" to dwm as known from Plan 9's
windowing system rio.

Clients marked with isterminal in config.h swallow a window opened by
any child process, e.g. running xclock in a terminal. Closing the xclock
window restores the terminal window in the current position.

This patch helps users spawning a lot of graphical programs from their
command line by avoiding cluttering the screen with many unusable
terminals. Being deep down in a directory hierarchy just does not make
the use of dmenu feasible.

Dependencies
        * libxcb
        * Xlib-libxcb
        * xcb-res

These dependencies are needed due to the use of the latest revision of
the X Resource Extension which is unsupported in vanilla Xlib.

Notes:

* The window swallowing functionality requires dwm to walk the process
  tree, which is an inherently OS-specific task. Only Linux and FreeBSD
  are supported at this time. Please contact one of the authors if you
  would like to help expand the list of supported operating systems.

* Only terminals created by local processes can swallow windows, and
  only windows created by local processes can be swallowed.

3 files changed, 187 insertions, 8 deletions

diff --git a/config.def.h b/config.def.h
index 1609683..c5e8fd5 100644
--- a/config.def.h
+++ b/config.def.h
@@ -32,8 +32,8 @@ static const Rule rules[] = {
 	 *	WM_CLASS(STRING) = instance, class
 	 *	WM_NAME(STRING) = title
 	 */
-	/* class      instance    title       tags mask     isfloating   monitor */
-	{  NULL,      NULL,       NULL,       0,            0,           -1 },
+	/* class      instance    title       tags mask     isfloating   isterminal noswallow monitor */
+	{ "st",       NULL,       NULL,       0,            0,           1,         1,        -1 },
 };
 
 /* layout(s) */
diff --git a/config.mk b/config.mk
index d609c42..8702404 100644
--- a/config.mk
+++ b/config.mk
@@ -23,7 +23,7 @@ FREETYPEINC = /usr/include/freetype2
 
 # includes and libs
 INCS = -I${X11INC} -I${FREETYPEINC}
-LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS} -lXrender
+LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS} -lXrender -lX11-xcb -lxcb -lxcb-res
 
 # flags
 CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
diff --git a/dwm.c b/dwm.c
index 5d4342a..38ffb86 100644
--- a/dwm.c
+++ b/dwm.c
@@ -40,6 +40,8 @@
 #include <X11/extensions/Xinerama.h>
 #endif /* XINERAMA */
 #include <X11/Xft/Xft.h>
+#include <X11/Xlib-xcb.h>
+#include <xcb/res.h>
 
 #include "drw.h"
 #include "util.h"
@@ -94,9 +96,11 @@ struct Client {
 	int basew, baseh, incw, inch, maxw, maxh, minw, minh, hintsvalid;
 	int bw, oldbw;
 	unsigned int tags;
-	int isfixed, isfloating, isurgent, neverfocus, oldstate, isfullscreen;
+	int isfixed, isfloating, isurgent, neverfocus, oldstate, isfullscreen, isterminal, noswallow;
+	pid_t pid;
 	Client *next;
 	Client *snext;
+	Client *swallowing;
 	Monitor *mon;
 	Window win;
 };
@@ -142,6 +146,8 @@ typedef struct {
 	const char *title;
 	unsigned int tags;
 	int isfloating;
+	int isterminal;
+	int noswallow;
 	int monitor;
 } Rule;
 
@@ -247,6 +253,13 @@ static void centeredmaster(Monitor *m);
 static void centeredfloatingmaster(Monitor *m);
 static void grid(Monitor *m);
 
+static pid_t getparentprocess(pid_t p);
+static int isdescprocess(pid_t p, pid_t c);
+static Client *swallowingclient(Window w);
+static Client *termforwin(const Client *c);
+static pid_t winpid(Window w);
+
+
 /* variables */
 static const char broken[] = "broken";
 static char stext[256];
@@ -285,6 +298,7 @@ static int useargb = 0;
 static Visual *visual;
 static int depth;
 static Colormap cmap;
+static xcb_connection_t *xcon;
 
 /* configuration, allows nested code to access above variables */
 #include "config.h"
@@ -325,6 +339,7 @@ applyrules(Client *c)
 		&& (!r->class || strstr(class, r->class))
 		&& (!r->instance || strstr(instance, r->instance)))
 		{
+			c->isterminal = r->isterminal;
 			c->isfloating = r->isfloating;
 			c->tags |= r->tags;
 			for (m = mons; m && m->num != r->monitor; m = m->next);
@@ -466,6 +481,47 @@ attachstack(Client *c)
 }
 
 void
+swallow(Client *p, Client *c)
+{
+	if (c->noswallow || c->isterminal)
+		return;
+
+	detach(c);
+	detachstack(c);
+
+	setclientstate(c, WithdrawnState);
+	XUnmapWindow(dpy, p->win);
+
+	p->swallowing = c;
+	c->mon = p->mon;
+
+	Window w = p->win;
+	p->win = c->win;
+	c->win = w;
+	updatetitle(p);
+	arrange(p->mon);
+	XMoveResizeWindow(dpy, p->win, p->x, p->y, p->w, p->h);
+	configure(p);
+	updateclientlist();
+}
+
+void
+unswallow(Client *c)
+{
+	c->win = c->swallowing->win;
+
+	free(c->swallowing);
+	c->swallowing = NULL;
+
+	updatetitle(c);
+	arrange(c->mon);
+	XMapWindow(dpy, c->win);
+	XMoveResizeWindow(dpy, c->win, c->x, c->y, c->w, c->h);
+	configure(c);
+	setclientstate(c, NormalState);
+}
+
+void
 buttonpress(XEvent *e)
 {
 	unsigned int i, x, click, occ = 0;
@@ -722,6 +778,9 @@ destroynotify(XEvent *e)
 
 	if ((c = wintoclient(ev->window)))
 		unmanage(c, 1);
+
+	else if ((c = swallowingclient(ev->window)))
+		unmanage(c->swallowing, 1);
 }
 
 void
@@ -1104,12 +1163,13 @@ killclient(const Arg *arg)
 void
 manage(Window w, XWindowAttributes *wa)
 {
-	Client *c, *t = NULL;
+	Client *c, *t = NULL, *term = NULL;
 	Window trans = None;
 	XWindowChanges wc;
 
 	c = ecalloc(1, sizeof(Client));
 	c->win = w;
+	c->pid = winpid(w);
 	/* geometry */
 	c->x = c->oldx = wa->x;
 	c->y = c->oldy = wa->y;
@@ -1124,6 +1184,7 @@ manage(Window w, XWindowAttributes *wa)
 	} else {
 		c->mon = selmon;
 		applyrules(c);
+		term = termforwin(c);
 	}
 
 	if (c->x + WIDTH(c) > c->mon->wx + c->mon->ww)
@@ -1166,6 +1227,8 @@ manage(Window w, XWindowAttributes *wa)
 	c->mon->sel = c;
 	arrange(c->mon);
 	XMapWindow(dpy, c->win);
+	if (term)
+		swallow(term, c);
 	focus(NULL);
 }
 
@@ -1979,6 +2042,20 @@ unmanage(Client *c, int destroyed)
 	Monitor *m = c->mon;
 	XWindowChanges wc;
 
+	if (c->swallowing) {
+		unswallow(c);
+		return;
+	}
+
+	Client *s = swallowingclient(c->win);
+	if (s) {
+		free(s->swallowing);
+		s->swallowing = NULL;
+		arrange(m);
+        focus(NULL);
+		return;
+	}
+
 	detach(c);
 	detachstack(c);
 	if (!destroyed) {
@@ -1994,9 +2071,12 @@ unmanage(Client *c, int destroyed)
 		XUngrabServer(dpy);
 	}
 	free(c);
-	focus(NULL);
-	updateclientlist();
-	arrange(m);
+
+	if (!s) {
+		arrange(m);
+		focus(NULL);
+		updateclientlist();
+	}
 }
 
 void
@@ -2284,6 +2364,103 @@ view(const Arg *arg)
 	arrange(selmon);
 }
 
+pid_t
+winpid(Window w)
+{
+	pid_t result = 0;
+
+	xcb_res_client_id_spec_t spec = {0};
+	spec.client = w;
+	spec.mask = XCB_RES_CLIENT_ID_MASK_LOCAL_CLIENT_PID;
+
+	xcb_generic_error_t *e = NULL;
+	xcb_res_query_client_ids_cookie_t c = xcb_res_query_client_ids(xcon, 1, &spec);
+	xcb_res_query_client_ids_reply_t *r = xcb_res_query_client_ids_reply(xcon, c, &e);
+
+	if (!r)
+		return (pid_t)0;
+
+	xcb_res_client_id_value_iterator_t i = xcb_res_query_client_ids_ids_iterator(r);
+	for (; i.rem; xcb_res_client_id_value_next(&i)) {
+		spec = i.data->spec;
+		if (spec.mask & XCB_RES_CLIENT_ID_MASK_LOCAL_CLIENT_PID) {
+			uint32_t *t = xcb_res_client_id_value_value(i.data);
+			result = *t;
+			break;
+		}
+	}
+
+	free(r);
+
+	if (result == (pid_t)-1)
+		result = 0;
+	return result;
+}
+
+pid_t
+getparentprocess(pid_t p)
+{
+	unsigned int v = 0;
+
+#ifdef __linux__
+	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);
+#endif /* __linux__ */
+
+	return (pid_t)v;
+}
+
+int
+isdescprocess(pid_t p, pid_t c)
+{
+	while (p != c && c != 0)
+		c = getparentprocess(c);
+
+	return (int)c;
+}
+
+Client *
+termforwin(const Client *w)
+{
+	Client *c;
+	Monitor *m;
+
+	if (!w->pid || w->isterminal)
+		return NULL;
+
+	for (m = mons; m; m = m->next) {
+		for (c = m->clients; c; c = c->next) {
+			if (c->isterminal && !c->swallowing && c->pid && isdescprocess(c->pid, w->pid))
+				return c;
+		}
+	}
+
+	return NULL;
+}
+
+Client *
+swallowingclient(Window w)
+{
+	Client *c;
+	Monitor *m;
+
+	for (m = mons; m; m = m->next) {
+		for (c = m->clients; c; c = c->next) {
+			if (c->swallowing && c->swallowing->win == w)
+				return c;
+		}
+	}
+
+	return NULL;
+}
+
 Client *
 wintoclient(Window w)
 {
@@ -2410,6 +2587,8 @@ main(int argc, char *argv[])
 		fputs("warning: no locale support\n", stderr);
 	if (!(dpy = XOpenDisplay(NULL)))
 		die("dwm: cannot open display");
+	if (!(xcon = XGetXCBConnection(dpy)))
+		die("dwm: cannot get xcb connection\n");
 	checkotherwm();
 	setup();
 #ifdef __OpenBSD__