chromium/ui/views/view_model.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_VIEWS_VIEW_MODEL_H_
#define UI_VIEWS_VIEW_MODEL_H_

#include <optional>
#include <vector>

#include "base/check_op.h"
#include "base/memory/raw_ptr.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/views/views_export.h"

namespace views {

class View;
class ViewModelUtils;

// Internal implementation of the templated ViewModelT class. Provides
// non-templated "unsafe" methods for ViewModelT to wrap around. Any methods
// that allow insertion of or access to a View* should be protected, and have a
// public method in the ViewModelT subclass that provides type-safe access to
// the correct View subclass.
class VIEWS_EXPORT ViewModelBase { … };

// ViewModelT is used to track an 'interesting' set of a views. Often times
// during animations views are removed after a delay, which makes for tricky
// coordinate conversion as you have to account for the possibility of the
// indices from the model not lining up with those you expect. This class lets
// you define the 'interesting' views and operate on those views.
template <class T>
class ViewModelT : public ViewModelBase { … };

// ViewModel is a collection of views with no specfic type. If all views have
// the same type, the use of ViewModelT is preferred so that the views can be
// retrieved without potentially unsafe downcasts.
ViewModel;

}  // namespace views

#endif  // UI_VIEWS_VIEW_MODEL_H_