Linux UI: Dynamically respond to changes in the scale factor

chrome/browser/ui/libgtkui/gtk_ui.h

 // Copyright (c) 2013 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.
 
 #ifndef CHROME_BROWSER_UI_LIBGTKUI_GTK_UI_H_
 #define CHROME_BROWSER_UI_LIBGTKUI_GTK_UI_H_
 
 #include <map>
 #include <memory>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "chrome/browser/ui/libgtkui/gtk_signal.h"
 #include "chrome/browser/ui/libgtkui/libgtkui_export.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/views/linux_ui/linux_ui.h"
 #include "ui/views/window/frame_buttons.h"
 
+typedef struct _GParamSpec GParamSpec;
 typedef struct _GtkStyle GtkStyle;
 typedef struct _GtkWidget GtkWidget;
 
 namespace libgtkui {
 class Gtk2KeyBindingsHandler;
 class GConfListener;
+class DeviceScaleFactorObserver;
 
 // Interface to GTK2 desktop features.
 //
 class GtkUi : public views::LinuxUI {
  public:
   GtkUi();
   ~GtkUi() override;
 
   typedef base::Callback<ui::NativeTheme*(aura::Window* window)>
       NativeThemeGetter;
@@ skipping 53 matching lines @@
   std::unique_ptr<views::Border> CreateNativeBorder(
       views::LabelButton* owning_button,
       std::unique_ptr<views::LabelButtonBorder> border) override;
   void AddWindowButtonOrderObserver(
       views::WindowButtonOrderObserver* observer) override;
   void RemoveWindowButtonOrderObserver(
       views::WindowButtonOrderObserver* observer) override;
   bool UnityIsRunning() override;
   NonClientMiddleClickAction GetNonClientMiddleClickAction() override;
   void NotifyWindowManagerStartupComplete() override;
+  void AddDeviceScaleFactorObserver(
+      views::DeviceScaleFactorObserver* observer) override;
+  void RemoveDeviceScaleFactorObserver(
+      views::DeviceScaleFactorObserver* observer) override;
 
   // ui::TextEditKeybindingDelegate:
   bool MatchEvent(const ui::Event& event,
                   std::vector<ui::TextEditCommandAuraLinux>* commands) override;
 
   // ui::Views::LinuxUI:
   void UpdateDeviceScaleFactor() override;
   float GetDeviceScaleFactor() const override;
 
  private:
   typedef std::map<int, SkColor> ColorMap;
   typedef std::map<int, color_utils::HSL> TintMap;
 
+  CHROMEG_CALLBACK_1(GtkUi,
+                     void,
+                     OnDeviceScaleFactorMaybeChanged,
+                     void*,
+                     GParamSpec*);
+
   // This method returns the colors webkit will use for the scrollbars. When no
   // colors are specified by the GTK+ theme, this function averages of the
   // thumb part and of the track colors.
   void SetScrollbarColors();
 
   // Extracts colors and tints from the GTK theme, both for the
   // ThemeService interface and the colors we send to webkit.
   void LoadGtkValues();
 
   // Sets the Xcursor theme and size with the GTK theme and size.
   void UpdateCursorTheme();
 
   // Updates |default_font_*|.
   void UpdateDefaultFont();
 
   // Gets a ChromeGtkFrame theme color; returns true on success.  No-op on gtk3.
   bool GetChromeStyleColor(const char* sytle_property,
                            SkColor* ret_color) const;
 
+  float GetRawDeviceScaleFactor();
+
   ui::NativeTheme* native_theme_;
 
-  // A GtkWindow object with the class "ChromeGtkFrame".
+  // On Gtk2, A GtkWindow object with the class "ChromeGtkFrame".  On
+  // Gtk3, a regular GtkWindow.
   GtkWidget* fake_window_;
 
   // Colors calculated by LoadGtkValues() that are given to the
   // caller while |use_gtk_| is true.
   ColorMap colors_;
 
   // Colors that we pass to WebKit. These are generated each time the theme
   // changes.
   SkColor focus_ring_color_;
   SkColor thumb_active_color_;
@@ skipping 19 matching lines @@
 #endif  // defined(USE_GCONF)
 
   // If either of these vectors are non-empty, they represent the current
   // window button configuration.
   std::vector<views::FrameButton> leading_buttons_;
   std::vector<views::FrameButton> trailing_buttons_;
 
   std::unique_ptr<Gtk2KeyBindingsHandler> key_bindings_handler_;
 
   // Objects to notify when the window frame button order changes.
-  base::ObserverList<views::WindowButtonOrderObserver> observer_list_;
+  base::ObserverList<views::WindowButtonOrderObserver>
+      window_button_order_observer_list_;
+
+  // Objects to notify when the device scale factor changes.
+  base::ObserverList<views::DeviceScaleFactorObserver>
+      device_scale_factor_observer_list_;
 
   // Whether we should lower the window on a middle click to the non client
   // area.
   NonClientMiddleClickAction middle_click_action_;
 
   // Used to override the native theme for a window. If no override is provided
   // or the callback returns nullptr, GtkUi will default to a NativeThemeGtk2
   // instance.
   NativeThemeGetter native_theme_overrider_;
 
   float device_scale_factor_ = 1.0f;
 
   DISALLOW_COPY_AND_ASSIGN(GtkUi);
 };
 
 }  // namespace libgtkui
 
 // Access point to the GTK2 desktop system. This should be the only symbol that
 // is exported in the library; everything else should be used through the
 // interface, because eventually this .so will be loaded through dlopen at
 // runtime so our main binary can conditionally load GTK2 or GTK3 or EFL or
 // QT or whatever.
 LIBGTKUI_EXPORT views::LinuxUI* BuildGtkUi();
 
 #endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK_UI_H_