app/active_window_watcher_x.cc

   1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include <X11/Xlib.h>
   6 #include <gdk/gdk.h>
   7 #include <gdk/gdkx.h>
   8
   9 #include "app/active_window_watcher_x.h"
  10
  11 static Atom kNetActiveWindowAtom = None;
  12
  13 // static
  14 ActiveWindowWatcherX* ActiveWindowWatcherX::GetInstance() {
  15   return Singleton<ActiveWindowWatcherX>::get();
  16 }
  17
  18 // static
  19 void ActiveWindowWatcherX::AddObserver(Observer* observer) {
  20   GetInstance()->observers_.AddObserver(observer);
  21 }
  22
  23 // static
  24 void ActiveWindowWatcherX::RemoveObserver(Observer* observer) {
  25   GetInstance()->observers_.RemoveObserver(observer);
  26 }
  27
  28 ActiveWindowWatcherX::ActiveWindowWatcherX() {
  29   Init();
  30 }
  31
  32 ActiveWindowWatcherX::~ActiveWindowWatcherX() {
  33 }
  34
  35 void ActiveWindowWatcherX::Init() {
  36   GdkAtom kNetActiveWindow = gdk_atom_intern("_NET_ACTIVE_WINDOW", FALSE);
  37   kNetActiveWindowAtom = gdk_x11_atom_to_xatom_for_display(
  38       gdk_screen_get_display(gdk_screen_get_default()), kNetActiveWindow);
  39
  40   GdkWindow* root = gdk_get_default_root_window();
  41
  42   // Set up X Event filter to listen for PropertyChange X events.  These events
  43   // tell us when the active window changes.
  44   // Don't use XSelectInput directly here, as gdk internally seems to cache the
  45   // mask and reapply XSelectInput after this, resetting any mask we set here.
  46   gdk_window_set_events(root,
  47                         static_cast<GdkEventMask>(gdk_window_get_events(root) |
  48                                                   GDK_PROPERTY_CHANGE_MASK));
  49   gdk_window_add_filter(NULL, &ActiveWindowWatcherX::OnWindowXEvent, this);
  50 }
  51
  52 void ActiveWindowWatcherX::NotifyActiveWindowChanged() {
  53   // We don't use gdk_screen_get_active_window() because it caches
  54   // whether or not the window manager supports _NET_ACTIVE_WINDOW.
  55   // This causes problems at startup for chromiumos.
  56   Atom type = None;
  57   int format = 0;  // size in bits of each item in 'property'
  58   long unsigned int num_items = 0, remaining_bytes = 0;
  59   unsigned char* property = NULL;
  60
  61   XGetWindowProperty(gdk_x11_get_default_xdisplay(),
  62                      GDK_WINDOW_XID(gdk_get_default_root_window()),
  63                      kNetActiveWindowAtom,
  64                      0,      // offset into property data to read
  65                      1,      // length to get in 32-bit quantities
  66                      False,  // deleted
  67                      AnyPropertyType,
  68                      &type,
  69                      &format,
  70                      &num_items,
  71                      &remaining_bytes,
  72                      &property);
  73
  74   // Check that the property was set and contained a single 32-bit item (we
  75   // don't check that remaining_bytes is 0, though, as XFCE's window manager
  76   // seems to actually store two values in the property for some unknown
  77   // reason.)
  78   if (format == 32 && num_items == 1) {
  79     int xid = *reinterpret_cast<int*>(property);
  80     GdkWindow* active_window = gdk_window_lookup(xid);
  81     FOR_EACH_OBSERVER(
  82         Observer,
  83         observers_,
  84         ActiveWindowChanged(active_window));
  85   }
  86   if (property)
  87     XFree(property);
  88 }
  89
  90 GdkFilterReturn ActiveWindowWatcherX::OnWindowXEvent(GdkXEvent* xevent,
  91     GdkEvent* event, gpointer window_watcher) {
  92   ActiveWindowWatcherX* watcher = reinterpret_cast<ActiveWindowWatcherX*>(
  93       window_watcher);
  94   XEvent* xev = static_cast<XEvent*>(xevent);
  95
  96   if (xev->xany.type == PropertyNotify &&
  97       xev->xproperty.atom == kNetActiveWindowAtom) {
  98     watcher->NotifyActiveWindowChanged();
  99   }
 100
 101   return GDK_FILTER_CONTINUE;
 102 }