linux: Get font DPI from GTK.

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 "base/command_line.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 641 matching lines @@
     g_free(gtk_rgba);
   }
 
   return subpixel_rendering;
 }
 
 std::string Gtk2UI::GetDefaultFontDescription() const {
   return default_font_description_;
 }
 
+double Gtk2UI::GetFontDPI() const {
+  GtkSettings* gtk_settings = gtk_settings_get_default();
+  CHECK(gtk_settings);
+  gint dpi = 0.0;

[msw, 2014/07/18 03:39:33]

nit: should this be -1 if for some reason g_object_get does nothing?

[Daniel Erat, 2014/07/18 04:20:25]

yep, and certainly not a double. thanks

+  g_object_get(gtk_settings, "gtk-xft-dpi", &dpi, NULL);
+
+  // GTK multiplies the DPI by 1024 before storing it.
+  return (dpi > 0) ? dpi / 1024.0 : dpi;
+}
+
 ui::SelectFileDialog* Gtk2UI::CreateSelectFileDialog(
     ui::SelectFileDialog::Listener* listener,
     ui::SelectFilePolicy* policy) const {
   return SelectFileDialogImpl::Create(listener, policy);
 }
 
 bool Gtk2UI::UnityIsRunning() {
   return unity::IsRunning();
 }
 
@@ skipping 676 matching lines @@
   ClearAllThemeData();
   LoadGtkValues();
   NativeThemeGtk2::instance()->NotifyObservers();
 }
 
 }  // namespace libgtk2ui
 
 views::LinuxUI* BuildGtk2UI() {
   return new libgtk2ui::Gtk2UI;
 }