util: move resource usage to its own file

4 files changed, 602 insertions, 519 deletions

diff --git a/libwnck/meson.build b/libwnck/meson.build
index aa60e83..9f714d0 100644
--- a/libwnck/meson.build
+++ b/libwnck/meson.build
@@ -63,6 +63,8 @@ sources = [
   'wnck-icon-cache.c',
   'wnck-image-menu-item-private.h',
   'wnck-image-menu-item.c',
+  'wnck-resource-usage-private.h',
+  'wnck-resource-usage.c',
   'workspace.c',
   'xutils.c',
 ]
diff --git a/libwnck/util.c b/libwnck/util.c
index 3760bc3..fa06c34 100644
--- a/libwnck/util.c
+++ b/libwnck/util.c
@@ -25,11 +25,9 @@
 #include "util.h"
 #include "xutils.h"
 #include "private.h"
+#include "wnck-resource-usage-private.h"
 #include <gdk/gdkx.h>
 #include <string.h>
-#ifdef HAVE_XRES
-#include <X11/extensions/XRes.h>
-#endif
 
 /**
  * SECTION:resource
@@ -60,81 +58,6 @@
  * #WnckApplication.
  */
 
-typedef enum
-{
-  WNCK_EXT_UNKNOWN = 0,
-  WNCK_EXT_FOUND = 1,
-  WNCK_EXT_MISSING = 2
-} WnckExtStatus;
-
-
-#if 0
-/* useful for debugging */
-static void
-_wnck_print_resource_usage (WnckResourceUsage *usage)
-{
-  if (!usage)
-    return;
-
-  g_print ("\twindows       : %d\n"
-           "\tGCs           : %d\n"
-           "\tfonts         : %d\n"
-           "\tpixmaps       : %d\n"
-           "\tpictures      : %d\n"
-           "\tglyphsets     : %d\n"
-           "\tcolormaps     : %d\n"
-           "\tpassive grabs : %d\n"
-           "\tcursors       : %d\n"
-           "\tunknowns      : %d\n"
-           "\tpixmap bytes  : %ld\n"
-           "\ttotal bytes   : ~%ld\n",
-           usage->n_windows,
-           usage->n_gcs,
-           usage->n_fonts,
-           usage->n_pixmaps,
-           usage->n_pictures,
-           usage->n_glyphsets,
-           usage->n_colormap_entries,
-           usage->n_passive_grabs,
-           usage->n_cursors,
-           usage->n_other,
-           usage->pixmap_bytes,
-           usage->total_bytes_estimate);
-}
-#endif
-
-static WnckExtStatus
-wnck_init_resource_usage (GdkDisplay *gdisplay)
-{
-  WnckExtStatus status;
-
-  status = GPOINTER_TO_INT (g_object_get_data (G_OBJECT (gdisplay),
-                                               "wnck-xres-status"));
-
-  if (status == WNCK_EXT_UNKNOWN)
-    {
-#ifdef HAVE_XRES
-      Display *xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
-      int event, error;
-
-      if (!XResQueryExtension (xdisplay, &event, &error))
-        status = WNCK_EXT_MISSING;
-      else
-        status = WNCK_EXT_FOUND;
-#else
-      status = WNCK_EXT_MISSING;
-#endif
-
-      g_object_set_data (G_OBJECT (gdisplay),
-                         "wnck-xres-status",
-                         GINT_TO_POINTER (status));
-    }
-
-  g_assert (status != WNCK_EXT_UNKNOWN);
-
-  return status;
-}
-
 /**
  * wnck_xid_read_resource_usage:
  * @gdk_display: a <classname>GdkDisplay</classname>.
@@ -155,430 +78,9 @@ wnck_xid_read_resource_usage (GdkDisplay        *gdisplay,
                               gulong             xid,
                               WnckResourceUsage *usage)
 {
-  g_return_if_fail (usage != NULL);
-
-  memset (usage, '\0', sizeof (*usage));
-
-  if (wnck_init_resource_usage (gdisplay) == WNCK_EXT_MISSING)
-    return;
-
-#ifdef HAVE_XRES
- {
-   Display *xdisplay;
-   XResType *types;
-   int n_types;
-   unsigned long pixmap_bytes;
-   int i;
-   Atom pixmap_atom;
-   Atom window_atom;
-   Atom gc_atom;
-   Atom picture_atom;
-   Atom glyphset_atom;
-   Atom font_atom;
-   Atom colormap_entry_atom;
-   Atom passive_grab_atom;
-   Atom cursor_atom;
-
-   types = NULL;
-   n_types = 0;
-   pixmap_bytes = 0;
-
-  xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
-
-  _wnck_error_trap_push (xdisplay);
-
-  XResQueryClientResources (xdisplay,
-                             xid, &n_types,
-                             &types);
-
-   XResQueryClientPixmapBytes (xdisplay,
-                               xid, &pixmap_bytes);
-   _wnck_error_trap_pop (xdisplay);
-
-   usage->pixmap_bytes = pixmap_bytes;
-
-   pixmap_atom = _wnck_atom_get ("PIXMAP");
-   window_atom = _wnck_atom_get ("WINDOW");
-   gc_atom = _wnck_atom_get ("GC");
-   font_atom = _wnck_atom_get ("FONT");
-   glyphset_atom = _wnck_atom_get ("GLYPHSET");
-   picture_atom = _wnck_atom_get ("PICTURE");
-   colormap_entry_atom = _wnck_atom_get ("COLORMAP ENTRY");
-   passive_grab_atom = _wnck_atom_get ("PASSIVE GRAB");
-   cursor_atom = _wnck_atom_get ("CURSOR");
-
-   i = 0;
-   while (i < n_types)
-     {
-       guint t = types[i].resource_type;
-
-       if (t == pixmap_atom)
-         usage->n_pixmaps += types[i].count;
-       else if (t == window_atom)
-         usage->n_windows += types[i].count;
-       else if (t == gc_atom)
-         usage->n_gcs += types[i].count;
-       else if (t == picture_atom)
-         usage->n_pictures += types[i].count;
-       else if (t == glyphset_atom)
-         usage->n_glyphsets += types[i].count;
-       else if (t == font_atom)
-         usage->n_fonts += types[i].count;
-       else if (t == colormap_entry_atom)
-         usage->n_colormap_entries += types[i].count;
-       else if (t == passive_grab_atom)
-         usage->n_passive_grabs += types[i].count;
-       else if (t == cursor_atom)
-         usage->n_cursors += types[i].count;
-       else
-         usage->n_other += types[i].count;
-
-       ++i;
-     }
-
-   XFree(types);
-
-   usage->total_bytes_estimate = usage->pixmap_bytes;
-
-   /* FIXME look in the X server source and come up with better
-    * answers here. Ideally we change XRes to return a number
-    * like this since it can do things like divide the cost of
-    * a shared resource among those sharing it.
-    */
-   usage->total_bytes_estimate += usage->n_windows * 24;
-   usage->total_bytes_estimate += usage->n_gcs * 24;
-   usage->total_bytes_estimate += usage->n_pictures * 24;
-   usage->total_bytes_estimate += usage->n_glyphsets * 24;
-   usage->total_bytes_estimate += usage->n_fonts * 1024;
-   usage->total_bytes_estimate += usage->n_colormap_entries * 24;
-   usage->total_bytes_estimate += usage->n_passive_grabs * 24;
-   usage->total_bytes_estimate += usage->n_cursors * 24;
-   usage->total_bytes_estimate += usage->n_other * 24;
- }
-#else /* HAVE_XRES */
-  g_assert_not_reached ();
-#endif /* HAVE_XRES */
+  _wnck_read_resource_usage_xid (gdisplay, xid, usage);
 }
 
-#ifdef HAVE_XRES
-static void
-wnck_pid_read_resource_usage_free_hash (gpointer data)
-{
-  g_slice_free (gulong, data);
-}
-
-static guint
-wnck_gulong_hash (gconstpointer v)
-{
-  /* FIXME: this is obvioulsy wrong, but nearly 100% of the time, the gulong
-   * only contains guint values */
-  return *(const guint *) v;
-}
-
-static gboolean
-wnck_gulong_equal (gconstpointer a,
-                   gconstpointer b)
-{
-  return *((const gulong *) a) == *((const gulong *) b);
-}
-
-static gulong
-wnck_check_window_for_pid (Screen *screen,
-                           Window  win,
-                           XID     match_xid,
-                           XID     mask)
-{
-  if ((win & ~mask) == match_xid) {
-    return _wnck_get_pid (screen, win);
-  }
-
-  return 0;
-}
-
-static void
-wnck_find_pid_for_resource_r (Display *xdisplay,
-                              Screen  *screen,
-                              Window   win_top,
-                              XID      match_xid,
-                              XID      mask,
-                              gulong  *xid,
-                              gulong  *pid)
-{
-  Status   qtres;
-  int      err;
-  Window   dummy;
-  Window  *children;
-  guint    n_children;
-  guint    i;
-  gulong   found_pid = 0;
-
-  while (gtk_events_pending ())
-    gtk_main_iteration ();
-
-  found_pid = wnck_check_window_for_pid (screen, win_top, match_xid, mask);
-  if (found_pid != 0)
-    {
-      *xid = win_top;
-      *pid = found_pid;
-    }
-
-  _wnck_error_trap_push (xdisplay);
-  qtres = XQueryTree (xdisplay, win_top, &dummy, &dummy,
-                      &children, &n_children);
-  err = _wnck_error_trap_pop (xdisplay);
-
-  if (!qtres || err != Success)
-    return;
-
-  for (i = 0; i < n_children; i++)
-    {
-      wnck_find_pid_for_resource_r (xdisplay, screen, children[i],
-                                    match_xid, mask, xid, pid);
-
-      if (*pid != 0)
-	break;
-    }
-
-  if (children)
-    XFree ((char *)children);
-}
-
-struct xresclient_state
-{
-  XResClient *clients;
-  int         n_clients;
-  int         next;
-  Display    *xdisplay;
-  GHashTable *hashtable_pid;
-};
-
-static struct xresclient_state xres_state = { NULL, 0, -1, NULL, NULL };
-static guint       xres_idleid = 0;
-static GHashTable *xres_hashtable = NULL;
-static time_t      start_update = 0;
-static time_t      end_update = 0;
-static guint       xres_removeid = 0;
-
-static void
-wnck_pid_read_resource_usage_xres_state_free (gpointer data)
-{
-  struct xresclient_state *state;
-
-  state = (struct xresclient_state *) data;
-
-  if (state->clients)
-    XFree (state->clients);
-  state->clients = NULL;
-
-  state->n_clients = 0;
-  state->next = -1;
-  state->xdisplay = NULL;
-
-  if (state->hashtable_pid)
-    g_hash_table_destroy (state->hashtable_pid);
-  state->hashtable_pid = NULL;
-}
-
-static gboolean
-wnck_pid_read_resource_usage_fill_cache (struct xresclient_state *state)
-{
-  int    i;
-  gulong pid;
-  gulong xid;
-  XID    match_xid;
-
-  if (state->next >= state->n_clients)
-    {
-      if (xres_hashtable)
-        g_hash_table_destroy (xres_hashtable);
-      xres_hashtable = state->hashtable_pid;
-      state->hashtable_pid = NULL;
-
-      time (&end_update);
-
-      xres_idleid = 0;
-      return FALSE;
-    }
-
-  match_xid = (state->clients[state->next].resource_base &
-               ~state->clients[state->next].resource_mask);
-
-  pid = 0;
-  xid = 0;
-
-  for (i = 0; i < ScreenCount (state->xdisplay); i++)
-    {
-      Screen *screen;
-      Window  root;
-
-      screen = ScreenOfDisplay (state->xdisplay, i);
-      root = RootWindow (state->xdisplay, i);
-
-      if (root == None)
-        continue;
-
-      wnck_find_pid_for_resource_r (state->xdisplay, screen, root, match_xid,
-                                    state->clients[state->next].resource_mask,
-                                    &xid, &pid);
-
-      if (pid != 0 && xid != 0)
-        break;
-    }
-
-  if (pid != 0 && xid != 0)
-    {
-      gulong *key;
-      gulong *value;
-
-      key = g_slice_new (gulong);
-      value = g_slice_new (gulong);
-      *key = pid;
-      *value = xid;
-      g_hash_table_insert (state->hashtable_pid, key, value);
-    }
-
-  state->next++;
-
-  return TRUE;
-}
-
-static void
-wnck_pid_read_resource_usage_start_build_cache (GdkDisplay *gdisplay)
-{
-  Display *xdisplay;
-  int      err;
-
-  if (xres_idleid != 0)
-    return;
-
-  time (&start_update);
-
-  xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
-
-  _wnck_error_trap_push (xdisplay);
-  XResQueryClients (xdisplay, &xres_state.n_clients, &xres_state.clients);
-  err = _wnck_error_trap_pop (xdisplay);
-
-  if (err != Success)
-    return;
-
-  xres_state.next = (xres_state.n_clients > 0) ? 0 : -1;
-  xres_state.xdisplay = xdisplay;
-  xres_state.hashtable_pid = g_hash_table_new_full (
-                                     wnck_gulong_hash,
-                                     wnck_gulong_equal,
-                                     wnck_pid_read_resource_usage_free_hash,
-                                     wnck_pid_read_resource_usage_free_hash);
-
-  xres_idleid = g_idle_add_full (
-                        G_PRIORITY_HIGH_IDLE,
-                        (GSourceFunc) wnck_pid_read_resource_usage_fill_cache,
-                        &xres_state, wnck_pid_read_resource_usage_xres_state_free);
-}
-
-static gboolean
-wnck_pid_read_resource_usage_destroy_hash_table (gpointer data)
-{
-  xres_removeid = 0;
-
-  if (xres_hashtable)
-    g_hash_table_destroy (xres_hashtable);
-
-  xres_hashtable = NULL;
-
-  return FALSE;
-}
-
-#define XRES_UPDATE_RATE_SEC 30
-static gboolean
-wnck_pid_read_resource_usage_from_cache (GdkDisplay        *gdisplay,
-                                         gulong             pid,
-                                         WnckResourceUsage *usage)
-{
-  gboolean  need_rebuild;
-  gulong   *xid_p;
-  int       cache_validity;
-
-  if (end_update == 0)
-    time (&end_update);
-
-  cache_validity = MAX (XRES_UPDATE_RATE_SEC, (end_update - start_update) * 2);
-
-  /* we rebuild the cache if it was never built or if it's old */
-  need_rebuild = (xres_hashtable == NULL ||
-                  (end_update < time (NULL) - cache_validity));
-
-  if (xres_hashtable)
-    {
-      /* clear the cache after quite some time, because it might not be used
-       * anymore */
-      if (xres_removeid != 0)
-        g_source_remove (xres_removeid);
-      xres_removeid = g_timeout_add_seconds (cache_validity * 2,
-                                             wnck_pid_read_resource_usage_destroy_hash_table,
-                                             NULL);
-    }
-
-  if (need_rebuild)
-    wnck_pid_read_resource_usage_start_build_cache (gdisplay);
-
-  if (xres_hashtable)
-    xid_p = g_hash_table_lookup (xres_hashtable, &pid);
-  else
-    xid_p = NULL;
-
-  if (xid_p)
-    {
-      wnck_xid_read_resource_usage (gdisplay, *xid_p, usage);
-      return TRUE;
-    }
-
-  return FALSE;
-}
-
-static void
-wnck_pid_read_resource_usage_no_cache (GdkDisplay        *gdisplay,
-                                       gulong             pid,
-                                       WnckResourceUsage *usage)
-{
-  Display *xdisplay;
-  int i;
-
-  xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
-
-  i = 0;
-  while (i < ScreenCount (xdisplay))
-    {
-      WnckScreen *screen;
-      GList *windows;
-      GList *tmp;
-
-      screen = wnck_screen_get (i);
-
-      g_assert (screen != NULL);
-
-      windows = wnck_screen_get_windows (screen);
-      tmp = windows;
-      while (tmp != NULL)
-        {
-          if (wnck_window_get_pid (tmp->data) == (int) pid)
-            {
-              wnck_xid_read_resource_usage (gdisplay,
-                                            wnck_window_get_xid (tmp->data),
-                                            usage);
-
-              /* stop on first window found */
-              return;
-            }
-
-          tmp = tmp->next;
-        }
-
-      ++i;
-    }
-}
-#endif /* HAVE_XRES */
-
 /**
  * wnck_pid_read_resource_usage:
  * @gdk_display: a <classname>GdkDisplay</classname>.
@@ -608,19 +110,7 @@ wnck_pid_read_resource_usage (GdkDisplay        *gdisplay,
                               gulong             pid,
                               WnckResourceUsage *usage)
 {
-  g_return_if_fail (usage != NULL);
-
-  memset (usage, '\0', sizeof (*usage));
-
-  if (wnck_init_resource_usage (gdisplay) == WNCK_EXT_MISSING)
-    return;
-
-#ifdef HAVE_XRES
-  if (!wnck_pid_read_resource_usage_from_cache (gdisplay, pid, usage))
-    /* the cache might not be built, might be outdated or might not contain
-     * data for a new X client, so try to fallback to something else */
-    wnck_pid_read_resource_usage_no_cache (gdisplay, pid, usage);
-#endif /* HAVE_XRES */
+  _wnck_read_resource_usage_pid (gdisplay, pid, usage);
 }
 
 static WnckClientType client_type = 0;
@@ -835,12 +325,7 @@ wnck_shutdown (void)
 {
   g_clear_object (&wnck_handle);
 
-#ifdef HAVE_XRES
-  if (xres_removeid != 0)
-    g_source_remove (xres_removeid);
-  xres_removeid = 0;
-  wnck_pid_read_resource_usage_destroy_hash_table (NULL);
-#endif
+  _wnck_read_resources_shutdown_all ();
 }
 
 void
diff --git a/libwnck/wnck-resource-usage-private.h b/libwnck/wnck-resource-usage-private.h
new file mode 100644
index 0000000..7470e8a
--- /dev/null
+++ b/libwnck/wnck-resource-usage-private.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2021 Alberts Muktupāvels
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef WNCK_RESOURCE_USAGE_PRIVATE_H
+#define WNCK_RESOURCE_USAGE_PRIVATE_H
+
+#include "util.h"
+
+G_BEGIN_DECLS
+
+void _wnck_read_resource_usage_xid     (GdkDisplay        *gdisplay,
+                                        gulong             xid,
+                                        WnckResourceUsage *usage);
+
+void _wnck_read_resource_usage_pid     (GdkDisplay        *gdisplay,
+                                        gulong             pid,
+                                        WnckResourceUsage *usage);
+
+void _wnck_read_resources_shutdown_all (void);
+
+G_END_DECLS
+
+#endif
diff --git a/libwnck/wnck-resource-usage.c b/libwnck/wnck-resource-usage.c
new file mode 100644
index 0000000..b413c53
--- /dev/null
+++ b/libwnck/wnck-resource-usage.c
@@ -0,0 +1,559 @@
+/*
+ * Copyright (C) 2001 Havoc Pennington
+ * Copyright (C) 2006-2007 Vincent Untz
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+#include "wnck-resource-usage-private.h"
+
+#include <gdk/gdkx.h>
+#ifdef HAVE_XRES
+#include <X11/extensions/XRes.h>
+#endif
+
+#include "screen.h"
+#include "window.h"
+#include "xutils.h"
+
+typedef enum
+{
+  WNCK_EXT_UNKNOWN = 0,
+  WNCK_EXT_FOUND = 1,
+  WNCK_EXT_MISSING = 2
+} WnckExtStatus;
+
+#if 0
+/* useful for debugging */
+static void
+_wnck_print_resource_usage (WnckResourceUsage *usage)
+{
+  if (!usage)
+    return;
+
+  g_print ("\twindows       : %d\n"
+           "\tGCs           : %d\n"
+           "\tfonts         : %d\n"
+           "\tpixmaps       : %d\n"
+           "\tpictures      : %d\n"
+           "\tglyphsets     : %d\n"
+           "\tcolormaps     : %d\n"
+           "\tpassive grabs : %d\n"
+           "\tcursors       : %d\n"
+           "\tunknowns      : %d\n"
+           "\tpixmap bytes  : %ld\n"
+           "\ttotal bytes   : ~%ld\n",
+           usage->n_windows,
+           usage->n_gcs,
+           usage->n_fonts,
+           usage->n_pixmaps,
+           usage->n_pictures,
+           usage->n_glyphsets,
+           usage->n_colormap_entries,
+           usage->n_passive_grabs,
+           usage->n_cursors,
+           usage->n_other,
+           usage->pixmap_bytes,
+           usage->total_bytes_estimate);
+}
+#endif
+
+static WnckExtStatus
+wnck_init_resource_usage (GdkDisplay *gdisplay)
+{
+  WnckExtStatus status;
+
+  status = GPOINTER_TO_INT (g_object_get_data (G_OBJECT (gdisplay),
+                                               "wnck-xres-status"));
+
+  if (status == WNCK_EXT_UNKNOWN)
+    {
+#ifdef HAVE_XRES
+      Display *xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
+      int event, error;
+
+      if (!XResQueryExtension (xdisplay, &event, &error))
+        status = WNCK_EXT_MISSING;
+      else
+        status = WNCK_EXT_FOUND;
+#else
+      status = WNCK_EXT_MISSING;
+#endif
+
+      g_object_set_data (G_OBJECT (gdisplay),
+                         "wnck-xres-status",
+                         GINT_TO_POINTER (status));
+    }
+
+  g_assert (status != WNCK_EXT_UNKNOWN);
+
+  return status;
+}
+
+#ifdef HAVE_XRES
+static void
+wnck_pid_read_resource_usage_free_hash (gpointer data)
+{
+  g_slice_free (gulong, data);
+}
+
+static guint
+wnck_gulong_hash (gconstpointer v)
+{
+  /* FIXME: this is obvioulsy wrong, but nearly 100% of the time, the gulong
+   * only contains guint values */
+  return *(const guint *) v;
+}
+
+static gboolean
+wnck_gulong_equal (gconstpointer a,
+                   gconstpointer b)
+{
+  return *((const gulong *) a) == *((const gulong *) b);
+}
+
+static gulong
+wnck_check_window_for_pid (Screen *screen,
+                           Window  win,
+                           XID     match_xid,
+                           XID     mask)
+{
+  if ((win & ~mask) == match_xid)
+    return _wnck_get_pid (screen, win);
+
+  return 0;
+}
+
+static void
+wnck_find_pid_for_resource_r (Display *xdisplay,
+                              Screen  *screen,
+                              Window   win_top,
+                              XID      match_xid,
+                              XID      mask,
+                              gulong  *xid,
+                              gulong  *pid)
+{
+  Status   qtres;
+  int      err;
+  Window   dummy;
+  Window  *children;
+  guint    n_children;
+  guint    i;
+  gulong   found_pid = 0;
+
+  while (gtk_events_pending ())
+    gtk_main_iteration ();
+
+  found_pid = wnck_check_window_for_pid (screen, win_top, match_xid, mask);
+  if (found_pid != 0)
+    {
+      *xid = win_top;
+      *pid = found_pid;
+    }
+
+  _wnck_error_trap_push (xdisplay);
+  qtres = XQueryTree (xdisplay, win_top, &dummy, &dummy,
+                      &children, &n_children);
+  err = _wnck_error_trap_pop (xdisplay);
+
+  if (!qtres || err != Success)
+    return;
+
+  for (i = 0; i < n_children; i++)
+    {
+      wnck_find_pid_for_resource_r (xdisplay, screen, children[i],
+                                    match_xid, mask, xid, pid);
+
+      if (*pid != 0)
+	break;
+    }
+
+  if (children)
+    XFree ((char *)children);
+}
+
+struct xresclient_state
+{
+  XResClient *clients;
+  int         n_clients;
+  int         next;
+  Display    *xdisplay;
+  GHashTable *hashtable_pid;
+};
+
+static struct xresclient_state xres_state = { NULL, 0, -1, NULL, NULL };
+static guint       xres_idleid = 0;
+static GHashTable *xres_hashtable = NULL;
+static time_t      start_update = 0;
+static time_t      end_update = 0;
+static guint       xres_removeid = 0;
+
+static void
+wnck_pid_read_resource_usage_xres_state_free (gpointer data)
+{
+  struct xresclient_state *state;
+
+  state = (struct xresclient_state *) data;
+
+  if (state->clients)
+    XFree (state->clients);
+  state->clients = NULL;
+
+  state->n_clients = 0;
+  state->next = -1;
+  state->xdisplay = NULL;
+
+  if (state->hashtable_pid)
+    g_hash_table_destroy (state->hashtable_pid);
+  state->hashtable_pid = NULL;
+}
+
+static gboolean
+wnck_pid_read_resource_usage_fill_cache (struct xresclient_state *state)
+{
+  int    i;
+  gulong pid;
+  gulong xid;
+  XID    match_xid;
+
+  if (state->next >= state->n_clients)
+    {
+      if (xres_hashtable)
+        g_hash_table_destroy (xres_hashtable);
+      xres_hashtable = state->hashtable_pid;
+      state->hashtable_pid = NULL;
+
+      time (&end_update);
+
+      xres_idleid = 0;
+      return FALSE;
+    }
+
+  match_xid = (state->clients[state->next].resource_base &
+               ~state->clients[state->next].resource_mask);
+
+  pid = 0;
+  xid = 0;
+
+  for (i = 0; i < ScreenCount (state->xdisplay); i++)
+    {
+      Screen *screen;
+      Window  root;
+
+      screen = ScreenOfDisplay (state->xdisplay, i);
+      root = RootWindow (state->xdisplay, i);
+
+      if (root == None)
+        continue;
+
+      wnck_find_pid_for_resource_r (state->xdisplay, screen, root, match_xid,
+                                    state->clients[state->next].resource_mask,
+                                    &xid, &pid);
+
+      if (pid != 0 && xid != 0)
+        break;
+    }
+
+  if (pid != 0 && xid != 0)
+    {
+      gulong *key;
+      gulong *value;
+
+      key = g_slice_new (gulong);
+      value = g_slice_new (gulong);
+      *key = pid;
+      *value = xid;
+      g_hash_table_insert (state->hashtable_pid, key, value);
+    }
+
+  state->next++;
+
+  return TRUE;
+}
+
+static void
+wnck_pid_read_resource_usage_start_build_cache (GdkDisplay *gdisplay)
+{
+  Display *xdisplay;
+  int      err;
+
+  if (xres_idleid != 0)
+    return;
+
+  time (&start_update);
+
+  xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
+
+  _wnck_error_trap_push (xdisplay);
+  XResQueryClients (xdisplay, &xres_state.n_clients, &xres_state.clients);
+  err = _wnck_error_trap_pop (xdisplay);
+
+  if (err != Success)
+    return;
+
+  xres_state.next = (xres_state.n_clients > 0) ? 0 : -1;
+  xres_state.xdisplay = xdisplay;
+  xres_state.hashtable_pid = g_hash_table_new_full (
+                                     wnck_gulong_hash,
+                                     wnck_gulong_equal,
+                                     wnck_pid_read_resource_usage_free_hash,
+                                     wnck_pid_read_resource_usage_free_hash);
+
+  xres_idleid = g_idle_add_full (
+                        G_PRIORITY_HIGH_IDLE,
+                        (GSourceFunc) wnck_pid_read_resource_usage_fill_cache,
+                        &xres_state, wnck_pid_read_resource_usage_xres_state_free);
+}
+
+static gboolean
+wnck_pid_read_resource_usage_destroy_hash_table (gpointer data)
+{
+  xres_removeid = 0;
+
+  if (xres_hashtable)
+    g_hash_table_destroy (xres_hashtable);
+
+  xres_hashtable = NULL;
+
+  return FALSE;
+}
+
+#define XRES_UPDATE_RATE_SEC 30
+static gboolean
+wnck_pid_read_resource_usage_from_cache (GdkDisplay        *gdisplay,
+                                         gulong             pid,
+                                         WnckResourceUsage *usage)
+{
+  gboolean  need_rebuild;
+  gulong   *xid_p;
+  int       cache_validity;
+
+  if (end_update == 0)
+    time (&end_update);
+
+  cache_validity = MAX (XRES_UPDATE_RATE_SEC, (end_update - start_update) * 2);
+
+  /* we rebuild the cache if it was never built or if it's old */
+  need_rebuild = (xres_hashtable == NULL ||
+                  (end_update < time (NULL) - cache_validity));
+
+  if (xres_hashtable)
+    {
+      /* clear the cache after quite some time, because it might not be used
+       * anymore */
+      if (xres_removeid != 0)
+        g_source_remove (xres_removeid);
+      xres_removeid = g_timeout_add_seconds (cache_validity * 2,
+                                             wnck_pid_read_resource_usage_destroy_hash_table,
+                                             NULL);
+    }
+
+  if (need_rebuild)
+    wnck_pid_read_resource_usage_start_build_cache (gdisplay);
+
+  if (xres_hashtable)
+    xid_p = g_hash_table_lookup (xres_hashtable, &pid);
+  else
+    xid_p = NULL;
+
+  if (xid_p)
+    {
+      wnck_xid_read_resource_usage (gdisplay, *xid_p, usage);
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+static void
+wnck_pid_read_resource_usage_no_cache (GdkDisplay        *gdisplay,
+                                       gulong             pid,
+                                       WnckResourceUsage *usage)
+{
+  Display *xdisplay;
+  int i;
+
+  xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
+
+  i = 0;
+  while (i < ScreenCount (xdisplay))
+    {
+      WnckScreen *screen;
+      GList *windows;
+      GList *tmp;
+
+      screen = wnck_screen_get (i);
+
+      g_assert (screen != NULL);
+
+      windows = wnck_screen_get_windows (screen);
+      tmp = windows;
+      while (tmp != NULL)
+        {
+          if (wnck_window_get_pid (tmp->data) == (int) pid)
+            {
+              wnck_xid_read_resource_usage (gdisplay,
+                                            wnck_window_get_xid (tmp->data),
+                                            usage);
+
+              /* stop on first window found */
+              return;
+            }
+
+          tmp = tmp->next;
+        }
+
+      ++i;
+    }
+}
+#endif /* HAVE_XRES */
+
+void
+_wnck_read_resource_usage_xid (GdkDisplay        *gdisplay,
+                               gulong             xid,
+                               WnckResourceUsage *usage)
+{
+  g_return_if_fail (usage != NULL);
+
+  memset (usage, '\0', sizeof (*usage));
+
+  if (wnck_init_resource_usage (gdisplay) == WNCK_EXT_MISSING)
+    return;
+
+#ifdef HAVE_XRES
+  {
+    Display *xdisplay;
+    XResType *types;
+    int n_types;
+    unsigned long pixmap_bytes;
+    int i;
+    Atom pixmap_atom;
+    Atom window_atom;
+    Atom gc_atom;
+    Atom picture_atom;
+    Atom glyphset_atom;
+    Atom font_atom;
+    Atom colormap_entry_atom;
+    Atom passive_grab_atom;
+    Atom cursor_atom;
+
+    types = NULL;
+    n_types = 0;
+    pixmap_bytes = 0;
+
+    xdisplay = GDK_DISPLAY_XDISPLAY (gdisplay);
+
+    _wnck_error_trap_push (xdisplay);
+
+    XResQueryClientResources (xdisplay, xid, &n_types, &types);
+
+    XResQueryClientPixmapBytes (xdisplay, xid, &pixmap_bytes);
+    _wnck_error_trap_pop (xdisplay);
+
+    usage->pixmap_bytes = pixmap_bytes;
+
+    pixmap_atom = _wnck_atom_get ("PIXMAP");
+    window_atom = _wnck_atom_get ("WINDOW");
+    gc_atom = _wnck_atom_get ("GC");
+    font_atom = _wnck_atom_get ("FONT");
+    glyphset_atom = _wnck_atom_get ("GLYPHSET");
+    picture_atom = _wnck_atom_get ("PICTURE");
+    colormap_entry_atom = _wnck_atom_get ("COLORMAP ENTRY");
+    passive_grab_atom = _wnck_atom_get ("PASSIVE GRAB");
+    cursor_atom = _wnck_atom_get ("CURSOR");
+
+    i = 0;
+    while (i < n_types)
+      {
+        guint t = types[i].resource_type;
+
+        if (t == pixmap_atom)
+          usage->n_pixmaps += types[i].count;
+        else if (t == window_atom)
+          usage->n_windows += types[i].count;
+        else if (t == gc_atom)
+          usage->n_gcs += types[i].count;
+        else if (t == picture_atom)
+          usage->n_pictures += types[i].count;
+        else if (t == glyphset_atom)
+          usage->n_glyphsets += types[i].count;
+        else if (t == font_atom)
+          usage->n_fonts += types[i].count;
+        else if (t == colormap_entry_atom)
+          usage->n_colormap_entries += types[i].count;
+        else if (t == passive_grab_atom)
+          usage->n_passive_grabs += types[i].count;
+        else if (t == cursor_atom)
+          usage->n_cursors += types[i].count;
+        else
+          usage->n_other += types[i].count;
+
+        ++i;
+      }
+
+    XFree(types);
+
+    usage->total_bytes_estimate = usage->pixmap_bytes;
+
+    /* FIXME look in the X server source and come up with better
+     * answers here. Ideally we change XRes to return a number
+     * like this since it can do things like divide the cost of
+     * a shared resource among those sharing it.
+     */
+    usage->total_bytes_estimate += usage->n_windows * 24;
+    usage->total_bytes_estimate += usage->n_gcs * 24;
+    usage->total_bytes_estimate += usage->n_pictures * 24;
+    usage->total_bytes_estimate += usage->n_glyphsets * 24;
+    usage->total_bytes_estimate += usage->n_fonts * 1024;
+    usage->total_bytes_estimate += usage->n_colormap_entries * 24;
+    usage->total_bytes_estimate += usage->n_passive_grabs * 24;
+    usage->total_bytes_estimate += usage->n_cursors * 24;
+    usage->total_bytes_estimate += usage->n_other * 24;
+  }
+#else /* HAVE_XRES */
+  g_assert_not_reached ();
+#endif /* HAVE_XRES */
+}
+
+void
+_wnck_read_resource_usage_pid (GdkDisplay        *gdisplay,
+                               gulong             pid,
+                               WnckResourceUsage *usage)
+{
+  g_return_if_fail (usage != NULL);
+
+  memset (usage, '\0', sizeof (*usage));
+
+  if (wnck_init_resource_usage (gdisplay) == WNCK_EXT_MISSING)
+    return;
+
+#ifdef HAVE_XRES
+  if (!wnck_pid_read_resource_usage_from_cache (gdisplay, pid, usage))
+    /* the cache might not be built, might be outdated or might not contain
+     * data for a new X client, so try to fallback to something else */
+    wnck_pid_read_resource_usage_no_cache (gdisplay, pid, usage);
+#endif /* HAVE_XRES */
+}
+
+void
+_wnck_read_resources_shutdown_all (void)
+{
+#ifdef HAVE_XRES
+  if (xres_removeid != 0)
+    g_source_remove (xres_removeid);
+  xres_removeid = 0;
+  wnck_pid_read_resource_usage_destroy_hash_table (NULL);
+#endif
+}