linux: Don't lower windows on middle-click on KDE 4.

chrome/browser/ui/libgtk2ui/gtk2_ui.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/libgtk2ui/gtk2_ui.h"
 
 #include <set>
 
 #include <pango/pango.h>
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
 #include "base/environment.h"
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
 #include "base/nix/mime_util_xdg.h"
+#include "base/nix/xdg_util.h"
 #include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/ui/libgtk2ui/app_indicator_icon.h"
 #include "chrome/browser/ui/libgtk2ui/chrome_gtk_frame.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_border.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_event_loop.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_key_bindings_handler.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_signal_registrar.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_status_icon.h"
@@ skipping 344 matching lines @@
     LOG(WARNING) << "Unexpected gtk-xft-rgba \"" << rgba << "\"";
     params.subpixel_rendering = gfx::FontRenderParams::SUBPIXEL_RENDERING_NONE;
   }
 
   g_free(hint_style);
   g_free(rgba);
 
   return params;
 }
 
+views::LinuxUI::NonClientMiddleClickAction GetDefaultMiddleClickAction() {
+  scoped_ptr<base::Environment> env(base::Environment::Create());
+  switch (base::nix::GetDesktopEnvironment(env.get())) {
+    case base::nix::DESKTOP_ENVIRONMENT_KDE4:
+      // Starting with KDE 4.4, windows' titlebars can be dragged with the
+      // middle mouse button to create tab groups. We don't support that in
+      // Chrome, but at least avoid lowering windows in response to middle
+      // clicks to avoid surprising users who expect the KDE behavior.
+      return views::LinuxUI::MIDDLE_CLICK_ACTION_NONE;
+    default:
+      return views::LinuxUI::MIDDLE_CLICK_ACTION_LOWER;
+  }
+}
+
 }  // namespace
 
-Gtk2UI::Gtk2UI() : middle_click_action_(MIDDLE_CLICK_ACTION_LOWER) {
+Gtk2UI::Gtk2UI() : middle_click_action_(GetDefaultMiddleClickAction()) {
   GtkInitFromCommandLine(*CommandLine::ForCurrentProcess());
 }
 
 void Gtk2UI::Initialize() {
   signals_.reset(new Gtk2SignalRegistrar);
 
   // Create our fake widgets.
   fake_window_ = gtk_window_new(GTK_WINDOW_TOPLEVEL);
   fake_frame_ = chrome_gtk_frame_new();
   fake_label_.Own(gtk_label_new(""));
@@ skipping 949 matching lines @@
   ClearAllThemeData();
   LoadGtkValues();
   NativeThemeGtk2::instance()->NotifyObservers();
 }
 
 }  // namespace libgtk2ui
 
 views::LinuxUI* BuildGtk2UI() {
   return new libgtk2ui::Gtk2UI;
 }