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// 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 UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
#define UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
#include "ui/views/views_export.h"
namespace gfx {
class Size;
}
namespace views {
class View;
// LayoutManager is used by View to accomplish the following:
//
// . Provides preferred sizing information, see GetPreferredSize() and
// GetPreferredHeightForWidth().
// . To position and size (aka layout) the children of the associated View. See
// Layout() for details.
//
// How a LayoutManager operates is specific to the LayoutManager. Non-trivial
// LayoutManagers calculate preferred size and layout information using the
// minimum and preferred size of the children of the View. That is, they
// make use of View::GetMinimumSize(), View::CalculatePreferredSize() and/or
// View::GetHeightForWidth().
class VIEWS_EXPORT LayoutManager {
public:
virtual ~LayoutManager();
// Notification that this LayoutManager has been installed on |host|.
virtual void Installed(View* host);
// Called by View::Layout() to position and size the children of |host|.
// Generally this queries |host| for its size and positions and sizes the
// children in a LayoutManager specific way.
virtual void Layout(View* host) = 0;
// Return the preferred size, which is typically the size needed to give each
// child of |host| its preferred size. Generally this is calculated using the
// View::CalculatePreferredSize() on each of the children of |host|.
virtual gfx::Size GetPreferredSize(const View* host) const = 0;
// Return the preferred height for a particular width. Generally this is
// calculated using View::GetHeightForWidth() or
// View::CalculatePreferredSize() on each of the children of |host|. Override
// this function if the preferred height varies based on the size. For
// example, a multi-line labels preferred height may change with the width.
// The default implementation returns GetPreferredSize().height().
virtual int GetPreferredHeightForWidth(const View* host, int width) const;
// Called when a View is added as a child of the View the LayoutManager has
// been installed on.
virtual void ViewAdded(View* host, View* view);
// Called when a View is removed as a child of the View the LayoutManager has
// been installed on. This function allows the LayoutManager to cleanup any
// state it has kept specific to a View.
virtual void ViewRemoved(View* host, View* view);
};
} // namespace views
#endif // UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
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