Support auto-hide taskbar for panels on Windows.

chrome/browser/ui/panels/auto_hiding_desktop_bar.h

+// Copyright (c) 2011 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_PANELS_AUTO_HIDING_DESKTOP_BAR_H_
+#define CHROME_BROWSER_UI_PANELS_AUTO_HIDING_DESKTOP_BAR_H_
+#pragma once
+
+#include "base/memory/ref_counted.h"
+
+namespace gfx {
+class Rect;
+}
+
+// Encapsulates the logic to deal with always-on-top auto-hiding desktop bars,
+// like Windows taskbar or MacOSX dock.
+// Note that the ref count is needed by using PostTask in the implementation of
+// MockAutoHidingDesktopBar that derives from AutoHidingDesktopBar.
+class AutoHidingDesktopBar : public base::RefCounted<AutoHidingDesktopBar> {
+ public:
+  // Indicates which screen edge the desktop bar is aligned to.
+  // We do not care about the desktop aligned to the top screen edge.
+  enum Alignment {
+    ALIGN_BOTTOM = 0,
+    ALIGN_LEFT = 1,
+    ALIGN_RIGHT = 2
+  };
+
+  enum Visibility {
+    VISIBLE,
+    ANIMATING,
+    HIDDEN
+  };
+
+  // Observer can listen to various events regarding the desktop bar changes.
+  class Observer {
+   public:
+    // Called when any of the desktop bars get their thickness changed.
+    // Note that if an auto-hiding desktop bar is moved from one edge
+    // to another edge, it will cause thickness changes to both edges.
+    virtual void OnAutoHidingDesktopBarThicknessChanged() = 0;
+
+    // Called when an auto-hiding desktop bar has its visibility changed.
+    virtual void OnAutoHidingDesktopBarVisibilityChanged(
+        Alignment alignment, Visibility visibility) = 0;
+  };
+
+  static AutoHidingDesktopBar* Create(Observer* observer);
+
+  virtual ~AutoHidingDesktopBar() { }
+
+  // This should be called each time when the work area is changed. We only
+  // care about the desktop bars that sit on the screen that hosts the specified
+  // work area.
+  virtual void UpdateWorkArea(const gfx::Rect& work_area) = 0;
+
+  // Returns true if there is a desktop bar that is aligned to the specified
+  // screen edge and set to auto-hide.
+  virtual bool IsEnabled(Alignment alignment) = 0;
+
+  // Returns the thickness of the desktop bar that is aligned to the specified
+  // screen edge, when it is visible. When the desktop bar is aligned to bottom
+  // edge, this is the height of the bar. If the desktop bar is aligned to
+  // left or right edge, this is the width of the bar.
+  virtual int GetThickness(Alignment alignment) const = 0;
+
+  // Returns the visibility state of the desktop bar that is aligned to the
+  // specified screen edge.
+  virtual Visibility GetVisibility(Alignment alignment) const = 0;
+};
+
+#endif  // CHROME_BROWSER_UI_PANELS_AUTO_HIDING_DESKTOP_BAR_H_