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// 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_BASE_MODELS_LIST_SELECTION_MODEL_H_
#define UI_BASE_MODELS_LIST_SELECTION_MODEL_H_
#include <stddef.h>
#include <optional>
#include "base/component_export.h"
#include "base/containers/flat_set.h"
namespace ui {
// Selection model represented as a list of indexes. In addition to the set of
// selected indices ListSelectionModel maintains the following:
//
// active: The index of the currently visible item in the list. This will be
// nullopt if nothing is selected.
//
// anchor: The index of the last item the user clicked on. Extending the
// selection extends it from this index. This will be nullopt if nothing
// is selected.
//
// Typically there is only one selected item, in which case the anchor and
// active index correspond to the same thing.
class COMPONENT_EXPORT(UI_BASE) ListSelectionModel {
public:
using SelectedIndices = base::flat_set<size_t>;
ListSelectionModel();
ListSelectionModel(const ListSelectionModel& other);
ListSelectionModel(ListSelectionModel&& other) noexcept;
~ListSelectionModel();
ListSelectionModel& operator=(const ListSelectionModel&);
ListSelectionModel& operator=(ListSelectionModel&&);
friend bool operator==(const ListSelectionModel&,
const ListSelectionModel&) = default;
// See class description for details of the anchor.
void set_anchor(std::optional<size_t> anchor) { anchor_ = anchor; }
std::optional<size_t> anchor() const { return anchor_; }
// See class description for details of active.
void set_active(std::optional<size_t> active) { active_ = active; }
std::optional<size_t> active() const { return active_; }
// True if nothing is selected.
bool empty() const { return selected_indices_.empty(); }
// Number of selected indices.
size_t size() const { return selected_indices_.size(); }
// Increments all indices >= |index|. For example, if the selection consists
// of [0, 1, 5] and this is invoked with 1, it results in [0, 2, 6]. This also
// updates the anchor and active indices.
// This is used when a new item is inserted into the model.
void IncrementFrom(size_t index);
// Shifts all indices > |index| down by 1. If |index| is selected, it is
// removed. For example, if the selection consists of [0, 1, 5] and this is
// invoked with 1, it results in [0, 4]. This is used when an item is
// removed.
void DecrementFrom(size_t index);
// Sets the anchor, active and selection to |index|.
void SetSelectedIndex(std::optional<size_t> index);
// Returns true if |index| is selected.
bool IsSelected(size_t index) const;
// Adds |index| to the selection. This does not change the active or anchor
// indices.
void AddIndexToSelection(size_t index);
// Adds indices between |index_start| and |index_end|, inclusive.
// This does not change the active or anchor indices.
void AddIndexRangeToSelection(size_t index_start, size_t index_end);
// Removes |index| from the selection. This does not change the active or
// anchor indices.
void RemoveIndexFromSelection(size_t index);
// Sets the selection from the anchor to |index|. If the anchor is empty,
// this sets the anchor, selection and active indices to |index|.
void SetSelectionFromAnchorTo(size_t index);
// Makes sure the tabs from the anchor to |index| are selected. This adds to
// the selection if there is an anchor and resets the selection to |index| if
// there is not an anchor.
void AddSelectionFromAnchorTo(size_t index);
// Invoked when an item moves. |old_index| is the original index, |new_index|
// is the target index, and |length| is the number of items that are moving.
//
// If moving to a greater index, |new_index| should be the index *after*
// removing the elements at the index range [old_index, old_index + length).
// For example, consider three list items 'A B C', to move A to the end of
// the list, this should be invoked with '0, 2, 1'.
void Move(size_t old_index, size_t new_index, size_t length);
// Sets the anchor and active to kUnselectedIndex, and removes all the
// selected indices.
void Clear();
// Returns the selected indices. The selection is always ordered in acending
// order.
const SelectedIndices& selected_indices() const { return selected_indices_; }
// Returns the state of the selection model as a string. The format is:
// 'active=X anchor=X selection=X X X...'.
std::string ToString() const;
private:
SelectedIndices selected_indices_;
std::optional<size_t> active_ = std::nullopt;
std::optional<size_t> anchor_ = std::nullopt;
};
} // namespace ui
#endif // UI_BASE_MODELS_LIST_SELECTION_MODEL_H_
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