[Toolbar] Base toolbar button class with background images for button states

chrome/browser/ui/views/toolbar/back_button.h

+// Copyright 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_VIEWS_TOOLBAR_BACK_BUTTON_H_
+#define CHROME_BROWSER_UI_VIEWS_TOOLBAR_BACK_BUTTON_H_
+
+#include "chrome/browser/ui/views/toolbar/toolbar_button.h"
+#include "ui/views/controls/button/button.h"

[Peter Kasting, 2013/11/26 22:24:31]

Nit: Is this #include necessary?  Seems like we could just forward-declare
ButtonListener?

[Greg Billock, 2013/11/27 14:22:35]

Done.

+
+namespace ui {
+class MenuModel;
+}
+
+// Modifies the ToolbarButton behavior by allowing the back button
+// to extend to the full margin if the toolbar is in a maximized state,
+// while keeping the usual margin between the drawn button and the edge
+// of the toolbar. This is done by adjusting the theme paint rect used
+// in the underlying button, and similarly adjusting the focus border.

[Peter Kasting, 2013/11/26 22:24:31]

Nit: This comment might be clearer:

A subclass of ToolbarButton to allow the back button's hittest region to extend
all the way to the start of the toolbar (i.e. the screen edge) in maximized
mode, to benefit from Fitt's Law.  The button images and focus border are still
drawn with the normal square shape.

[Greg Billock, 2013/11/27 14:22:35]

Sounds good.

+class BackButton : public ToolbarButton {
+ public:
+  // Takes ownership of the |model|, which can be null if no menu
+  // is to be shown.
+  BackButton(views::ButtonListener* listener, ui::MenuModel* model);
+  virtual ~BackButton();
+
+  void SetLeftMargin(int margin);

[Peter Kasting, 2013/11/26 22:24:31]

Nit: Consider using "start" or "leading" in place of "left" here and below to
avoid being misleading in RTL layouts.

[Greg Billock, 2013/11/27 14:22:35]

Done.

+
+ protected:
+  virtual gfx::Rect GetThemePaintRect() const OVERRIDE;
+
+ private:
+  // Any leading margin to be applied. Used when the back button is in
+  // a maximized state to extend to the full window width.
+  int margin_left_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackButton);
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_TOOLBAR_BACK_BUTTON_H_