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Previously, the selection base and extent were stored internally as iterators over text_. Since iterators must be treated as invalidated whenever the underlying container changes, this requires that selection_base_ and selection_extent_ be re-assigned after every change to text_. This is not currently particularly problematic, but once we add fields to track the base and extent of the composing region for multi-step input method support, as well as support for the sub-range within the composing region to which edits/completions apply, we end up having to regenerate a lot of iterators with each change, many of which are logically unchanged in position. A side benefit is that this simplifies inspection of these fields when debugging.
133 lines
4.0 KiB
C++
133 lines
4.0 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef FLUTTER_SHELL_PLATFORM_CPP_TEXT_INPUT_MODEL_H_
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#define FLUTTER_SHELL_PLATFORM_CPP_TEXT_INPUT_MODEL_H_
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#include <algorithm>
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#include <memory>
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#include <string>
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namespace flutter {
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// Handles underlying text input state, using a simple ASCII model.
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//
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// Ignores special states like "insert mode" for now.
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class TextInputModel {
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public:
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TextInputModel();
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virtual ~TextInputModel();
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// Sets the text.
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//
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// Resets the selection base and extent.
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void SetText(const std::string& text);
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// Attempts to set the text selection.
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//
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// Returns false if the base or extent are out of bounds.
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bool SetSelection(size_t base, size_t extent);
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// Adds a Unicode code point.
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//
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// Either appends after the cursor (when selection base and extent are the
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// same), or deletes the selected text, replacing it with the given
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// code point.
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void AddCodePoint(char32_t c);
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// Adds UTF-16 text.
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//
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// Either appends after the cursor (when selection base and extent are the
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// same), or deletes the selected text, replacing it with the given text.
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void AddText(const std::u16string& text);
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// Adds UTF-8 text.
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//
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// Either appends after the cursor (when selection base and extent are the
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// same), or deletes the selected text, replacing it with the given text.
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void AddText(const std::string& text);
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// Deletes either the selection, or one character ahead of the cursor.
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//
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// Deleting one character ahead of the cursor occurs when the selection base
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// and extent are the same.
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//
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// Returns true if any deletion actually occurred.
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bool Delete();
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// Deletes text near the cursor.
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//
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// A section is made starting at @offset code points past the cursor (negative
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// values go before the cursor). @count code points are removed. The selection
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// may go outside the bounds of the text and will result in only the part
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// selection that covers the available text being deleted. The existing
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// selection is ignored and removed after this operation.
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//
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// Returns true if any deletion actually occurred.
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bool DeleteSurrounding(int offset_from_cursor, int count);
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// Deletes either the selection, or one character behind the cursor.
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//
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// Deleting one character behind the cursor occurs when the selection base
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// and extent are the same.
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//
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// Returns true if any deletion actually occurred.
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bool Backspace();
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// Attempts to move the cursor backward.
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//
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// Returns true if the cursor could be moved. If a selection is active, moves
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// to the start of the selection.
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bool MoveCursorBack();
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// Attempts to move the cursor forward.
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//
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// Returns true if the cursor could be moved. If a selection is active, moves
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// to the end of the selection.
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bool MoveCursorForward();
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// Attempts to move the cursor to the beginning.
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//
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// Returns true if the cursor could be moved.
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bool MoveCursorToBeginning();
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// Attempts to move the cursor to the back.
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//
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// Returns true if the cursor could be moved.
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bool MoveCursorToEnd();
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// Gets the current text as UTF-8.
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std::string GetText() const;
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// Gets the cursor position as a byte offset in UTF-8 string returned from
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// GetText().
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int GetCursorOffset() const;
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// The position where the selection starts.
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int selection_base() const { return selection_base_; }
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// The position of the cursor.
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int selection_extent() const { return selection_extent_; }
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private:
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void DeleteSelected();
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std::u16string text_;
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size_t selection_base_ = 0;
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size_t selection_extent_ = 0;
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// Returns the left hand side of the selection.
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size_t selection_start() {
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return std::min(selection_base_, selection_extent_);
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}
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// Returns the right hand side of the selection.
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size_t selection_end() {
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return std::max(selection_base_, selection_extent_);
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}
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};
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} // namespace flutter
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#endif // FLUTTER_SHELL_PLATFORM_CPP_TEXT_INPUT_MODEL_H_
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