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// Copyright 2022 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_IME_SURROUNDING_TEXT_TRACKER_H_
#define UI_BASE_IME_SURROUNDING_TEXT_TRACKER_H_
#include <deque>
#include <string>
#include <string_view>
#include <variant>
#include "base/component_export.h"
#include "base/functional/callback.h"
#include "ui/base/ime/text_input_client.h"
#include "ui/gfx/range/range.h"
namespace ui {
struct CompositionText;
// Tracks the surrounding text. Because IMF works in an asynchronous manner,
// there will be timing gap that IM-Engine sends some request to the text input
// client, and the commit is actually notified.
// This class gives it a try to fill the gap by caching and emulating the
// latest surrounding text under the assumption that text editing requests are
// processed in a common manner.
class COMPONENT_EXPORT(UI_BASE_IME) SurroundingTextTracker {
public:
struct COMPONENT_EXPORT(UI_BASE_IME) State {
// Returns the range of the surrounding text in UTF-16.
gfx::Range GetSurroundingTextRange() const;
// Returns the string piece of the composition range of the
// |surrounding_text|.
// If composition is out of the range, nullopt will be returned.
std::optional<std::u16string_view> GetCompositionText() const;
// Whole surrounding text, specifically this may include composition text.
std::u16string surrounding_text;
// Offset of the surrounding_text within the text input client.
// This does not affect to either selection nor composition.
size_t utf16_offset;
// Selection range. If it is empty, it means the cursor. Must not be
// InvalidRange. Must be fit in |surrounding_text| range.
gfx::Range selection;
// Composition range if it has. Maybe empty if there's no composition text.
// Must not be InvalidRange. Must be fit in |surrounding_text| range.
gfx::Range composition;
};
// The initial state is no-surrounding text, cursor at 0, and no composition.
SurroundingTextTracker();
SurroundingTextTracker(const SurroundingTextTracker&) = delete;
SurroundingTextTracker& operator=(const SurroundingTextTracker&) = delete;
~SurroundingTextTracker();
const State& predicted_state() const { return predicted_state_; }
// Resets the internal state, including composition state, surrounding text
// and held histories. Used when the entire state needs to be reset.
// TODO(b/267944900): Investigate if this is still needed once
// kWaylandCancelComposition flag is enabled by default.
void Reset();
// Resets only the composition state and held histories.
// Used when only the composition state is cancelled by the input field.
void CancelComposition();
enum class UpdateResult {
// Expected update entry is found in |expected_updates_|.
kUpdated,
// No update entry corresponding to the given arguments is found.
// All the states are reset to the given arguments.
kReset,
};
// Expected to be called on surrounding text update event from text input
// client. If there was some known state matching to the arguments,
// forgets the state histories before it, and returns kUpdateFoundInHistory.
// Otherwise, forgets everything and reset by the state of the given
// arguments, then returns kHistoryIsReset.
// Note intentiontally ignored composition text.
UpdateResult Update(const std::u16string_view surrounding_text,
size_t utf16_offset,
const gfx::Range& selection);
// The following methods are used to guess new surrounding text state.
// See TextInputClient for detailed behavior.
void OnSetEditableSelectionRange(const gfx::Range& range);
void OnSetCompositionText(const ui::CompositionText& composition);
void OnSetCompositionFromExistingText(const gfx::Range& range);
void OnConfirmCompositionText(bool keep_selection);
void OnClearCompositionText();
void OnInsertText(const std::u16string_view text,
TextInputClient::InsertTextCursorBehavior cursor_behavior);
void OnExtendSelectionAndDelete(size_t before, size_t after);
private:
// History of events and their expected states.
struct Entry {
State state;
base::RepeatingClosure command;
Entry(State state, base::RepeatingClosure command);
// Copy/Move-able.
Entry(const Entry&);
Entry(Entry&& entry);
Entry& operator=(const Entry&);
Entry& operator=(Entry&&);
~Entry();
};
void ResetInternal(std::u16string_view surrounding_text,
size_t utf16_offset,
const gfx::Range& selection);
// The latest known state.
State predicted_state_;
std::deque<Entry> expected_updates_;
};
} // namespace ui
#endif // UI_BASE_IME_SURROUNDING_TEXT_TRACKER_H_
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