text_selection.dart

part of flutter_extended_text_field;

abstract class ExtendedTextSelectionGestureDetectorBuilderDelegate {
  /// [GlobalKey] to the [EditableText] for which the
  /// [ExtendedTextSelectionGestureDetectorBuilder] will build a [TextSelectionGestureDetector].
  GlobalKey<ExtendedEditableTextState> get editableTextKey;

  /// Whether the textfield should respond to force presses.
  bool get forcePressEnabled;

  /// Whether the user may select text in the textfield.
  bool get selectionEnabled;
}

class ExtendedTextSelectionGestureDetectorBuilder {
  /// Creates a [ExtendedTextSelectionGestureDetectorBuilder].
  ///
  /// The [delegate] must not be null.
  ExtendedTextSelectionGestureDetectorBuilder({
    required this.delegate,
  }) : assert(delegate != null);

  /// The delegate for this [ExtendedTextSelectionGestureDetectorBuilder].
  ///
  /// The delegate provides the builder with information about what actions can
  /// currently be performed on the textfield. Based on this, the builder adds
  /// the correct gesture handlers to the gesture detector.
  @protected
  final ExtendedTextSelectionGestureDetectorBuilderDelegate delegate;

  /// Returns true if lastSecondaryTapDownPosition was on selection.
  bool get _lastSecondaryTapWasOnSelection {
    assert(renderEditable.lastSecondaryTapDownPosition != null);
    if (renderEditable.selection == null) {
      return false;
    }

    final TextPosition textPosition = renderEditable.getPositionForPoint(
      renderEditable.lastSecondaryTapDownPosition!,
    );

    return renderEditable.selection!.start <= textPosition.offset &&
        renderEditable.selection!.end >= textPosition.offset;
  }

  // Expand the selection to the given global position.
  //
  // Either base or extent will be moved to the last tapped position, whichever
  // is closest. The selection will never shrink or pivot, only grow.
  //
  // See also:
  //
  //   * [_extendSelection], which is similar but pivots the selection around
  //     the base.
  void _expandSelection(Offset offset, SelectionChangedCause cause) {
    assert(cause != null);
    assert(offset != null);
    assert(renderEditable.selection?.baseOffset != null);

    final TextPosition tappedPosition =
        renderEditable.getPositionForPoint(offset);
    final TextSelection selection = renderEditable.selection!;
    final bool baseIsCloser =
        (tappedPosition.offset - selection.baseOffset).abs() <
            (tappedPosition.offset - selection.extentOffset).abs();
    final TextSelection nextSelection = selection.copyWith(
      baseOffset: baseIsCloser ? selection.extentOffset : selection.baseOffset,
      extentOffset: tappedPosition.offset,
    );

    editableText.userUpdateTextEditingValue(
      editableText.textEditingValue.copyWith(
        selection: nextSelection,
      ),
      cause,
    );
  }

  // Extend the selection to the given global position.
  //
  // Holds the base in place and moves the extent.
  //
  // See also:
  //
  //   * [_expandSelection], which is similar but always increases the size of
  //     the selection.
  void _extendSelection(Offset offset, SelectionChangedCause cause) {
    assert(cause != null);
    assert(offset != null);
    assert(renderEditable.selection?.baseOffset != null);

    final TextPosition tappedPosition =
        renderEditable.getPositionForPoint(offset);
    final TextSelection selection = renderEditable.selection!;
    final TextSelection nextSelection = selection.copyWith(
      extentOffset: tappedPosition.offset,
    );

    editableText.userUpdateTextEditingValue(
      editableText.textEditingValue.copyWith(
        selection: nextSelection,
      ),
      cause,
    );
  }

  /// Whether to show the selection toolbar.
  ///
  /// It is based on the signal source when a [onTapDown] is called. This getter
  /// will return true if current [onTapDown] event is triggered by a touch or
  /// a stylus.
  bool get shouldShowSelectionToolbar => _shouldShowSelectionToolbar;
  bool _shouldShowSelectionToolbar = true;

  /// The [State] of the [EditableText] for which the builder will provide a
  /// [TextSelectionGestureDetector].
  @protected
  ExtendedEditableTextState get editableText =>
      delegate.editableTextKey.currentState!;

  /// The [RenderObject] of the [EditableText] for which the builder will
  /// provide a [TextSelectionGestureDetector].
  @protected
  RenderEditable get renderEditable => editableText.renderEditable;

  // The viewport offset pixels of the [RenderEditable] at the last drag start.
  double _dragStartViewportOffset = 0.0;

  // True iff a tap + shift has been detected but the tap has not yet come up.
  bool _isShiftTapping = false;

  /// Handler for [TextSelectionGestureDetector.onTapDown].
  ///
  /// By default, it forwards the tap to [RenderEditable.handleTapDown] and sets
  /// [shouldShowSelectionToolbar] to true if the tap was initiated by a finger or stylus.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onTapDown], which triggers this callback.
  @protected
  void onTapDown(TapDownDetails details) {
    renderEditable.handleTapDown(details);
    // The selection overlay should only be shown when the user is interacting
    // through a touch screen (via either a finger or a stylus). A mouse shouldn't
    // trigger the selection overlay.
    // For backwards-compatibility, we treat a null kind the same as touch.
    final PointerDeviceKind? kind = details.kind;
    _shouldShowSelectionToolbar = kind == null ||
        kind == PointerDeviceKind.touch ||
        kind == PointerDeviceKind.stylus;

    // Handle shift + click selection if needed.
    final bool isShiftPressed =
        HardwareKeyboard.instance.logicalKeysPressed.any(<LogicalKeyboardKey>{
      LogicalKeyboardKey.shiftLeft,
      LogicalKeyboardKey.shiftRight,
    }.contains);
    if (isShiftPressed && renderEditable.selection?.baseOffset != null) {
      _isShiftTapping = true;
      switch (defaultTargetPlatform) {
        case TargetPlatform.iOS:
        case TargetPlatform.macOS:
          _expandSelection(details.globalPosition, SelectionChangedCause.tap);
          break;
        case TargetPlatform.android:
        case TargetPlatform.fuchsia:
        case TargetPlatform.linux:
        case TargetPlatform.windows:
          _extendSelection(details.globalPosition, SelectionChangedCause.tap);
          break;
      }
    }
  }

  /// Handler for [TextSelectionGestureDetector.onForcePressStart].
  ///
  /// By default, it selects the word at the position of the force press,
  /// if selection is enabled.
  ///
  /// This callback is only applicable when force press is enabled.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onForcePressStart], which triggers this
  ///    callback.
  @protected
  void onForcePressStart(ForcePressDetails details) {
    assert(delegate.forcePressEnabled);
    _shouldShowSelectionToolbar = true;
    if (delegate.selectionEnabled) {
      renderEditable.selectWordsInRange(
        from: details.globalPosition,
        cause: SelectionChangedCause.forcePress,
      );
    }
  }

  /// Handler for [TextSelectionGestureDetector.onForcePressEnd].
  ///
  /// By default, it selects words in the range specified in [details] and shows
  /// toolbar if it is necessary.
  ///
  /// This callback is only applicable when force press is enabled.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onForcePressEnd], which triggers this
  ///    callback.
  @protected
  void onForcePressEnd(ForcePressDetails details) {
    assert(delegate.forcePressEnabled);
    renderEditable.selectWordsInRange(
      from: details.globalPosition,
      cause: SelectionChangedCause.forcePress,
    );
    if (shouldShowSelectionToolbar) editableText.showToolbar();
  }

  /// Handler for [TextSelectionGestureDetector.onSingleTapUp].
  ///
  /// By default, it selects word edge if selection is enabled.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onSingleTapUp], which triggers
  ///    this callback.
  @protected
  void onSingleTapUp(TapUpDetails details) {
    if (_isShiftTapping) {
      _isShiftTapping = false;
      return;
    }

    if (delegate.selectionEnabled) {
      switch (defaultTargetPlatform) {
        case TargetPlatform.iOS:
        case TargetPlatform.macOS:
          switch (details.kind) {
            case PointerDeviceKind.mouse:
            case PointerDeviceKind.stylus:
            case PointerDeviceKind.invertedStylus:
              // Precise devices should place the cursor at a precise position.
              renderEditable.selectPosition(cause: SelectionChangedCause.tap);
              break;
            case PointerDeviceKind.touch:
            case PointerDeviceKind.unknown:
              // On macOS/iOS/iPadOS a touch tap places the cursor at the edge
              // of the word.
              renderEditable.selectWordEdge(cause: SelectionChangedCause.tap);
              break;
          }
          break;
        case TargetPlatform.android:
        case TargetPlatform.fuchsia:
        case TargetPlatform.linux:
        case TargetPlatform.windows:
          renderEditable.selectPosition(cause: SelectionChangedCause.tap);
          break;
      }
    }
  }

  /// Handler for [TextSelectionGestureDetector.onSingleTapCancel].
  ///
  /// By default, it services as place holder to enable subclass override.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onSingleTapCancel], which triggers
  ///    this callback.
  @protected
  void onSingleTapCancel() {
    /* Subclass should override this method if needed. */
  }

  /// Handler for [TextSelectionGestureDetector.onSingleLongTapStart].
  ///
  /// By default, it selects text position specified in [details] if selection
  /// is enabled.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onSingleLongTapStart], which triggers
  ///    this callback.
  @protected
  void onSingleLongTapStart(LongPressStartDetails details) {
    if (delegate.selectionEnabled) {
      renderEditable.selectPositionAt(
        from: details.globalPosition,
        cause: SelectionChangedCause.longPress,
      );
    }
  }

  /// Handler for [TextSelectionGestureDetector.onSingleLongTapMoveUpdate].
  ///
  /// By default, it updates the selection location specified in [details] if
  /// selection is enabled.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onSingleLongTapMoveUpdate], which
  ///    triggers this callback.
  @protected
  void onSingleLongTapMoveUpdate(LongPressMoveUpdateDetails details) {
    if (delegate.selectionEnabled) {
      renderEditable.selectPositionAt(
        from: details.globalPosition,
        cause: SelectionChangedCause.longPress,
      );
    }
  }

  /// Handler for [TextSelectionGestureDetector.onSingleLongTapEnd].
  ///
  /// By default, it shows toolbar if necessary.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onSingleLongTapEnd], which triggers this
  ///    callback.
  @protected
  void onSingleLongTapEnd(LongPressEndDetails details) {
    if (shouldShowSelectionToolbar) editableText.showToolbar();
  }

  /// Handler for [TextSelectionGestureDetector.onSecondaryTap].
  ///
  /// By default, selects the word if possible and shows the toolbar.
  @protected
  void onSecondaryTap() {
    if (delegate.selectionEnabled) {
      if (!_lastSecondaryTapWasOnSelection) {
        renderEditable.selectWord(cause: SelectionChangedCause.tap);
      }
      if (shouldShowSelectionToolbar) {
        editableText.hideToolbar();
        editableText.showToolbar();
      }
    }
  }

  /// Handler for [TextSelectionGestureDetector.onSecondaryTapDown].
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onSecondaryTapDown], which triggers this
  ///    callback.
  ///  * [onSecondaryTap], which is typically called after this.
  @protected
  void onSecondaryTapDown(TapDownDetails details) {
    renderEditable.handleSecondaryTapDown(details);
    _shouldShowSelectionToolbar = true;
  }

  /// Handler for [TextSelectionGestureDetector.onDoubleTapDown].
  ///
  /// By default, it selects a word through [RenderEditable.selectWord] if
  /// selectionEnabled and shows toolbar if necessary.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onDoubleTapDown], which triggers this
  ///    callback.
  @protected
  void onDoubleTapDown(TapDownDetails details) {
    if (delegate.selectionEnabled) {
      renderEditable.selectWord(cause: SelectionChangedCause.tap);
      if (shouldShowSelectionToolbar) editableText.showToolbar();
    }
  }

  /// Handler for [TextSelectionGestureDetector.onDragSelectionStart].
  ///
  /// By default, it selects a text position specified in [details].
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onDragSelectionStart], which triggers
  ///    this callback.
  @protected
  void onDragSelectionStart(DragStartDetails details) {
    if (!delegate.selectionEnabled) return;
    final PointerDeviceKind? kind = details.kind;
    _shouldShowSelectionToolbar = kind == null ||
        kind == PointerDeviceKind.touch ||
        kind == PointerDeviceKind.stylus;

    renderEditable.selectPositionAt(
      from: details.globalPosition,
      cause: SelectionChangedCause.drag,
    );

    _dragStartViewportOffset = renderEditable.offset.pixels;
  }

  /// Handler for [TextSelectionGestureDetector.onDragSelectionUpdate].
  ///
  /// By default, it updates the selection location specified in the provided
  /// details objects.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onDragSelectionUpdate], which triggers
  ///    this callback./lib/src/material/text_field.dart
  @protected
  void onDragSelectionUpdate(
      DragStartDetails startDetails, DragUpdateDetails updateDetails) {
    if (!delegate.selectionEnabled) return;

    // Adjust the drag start offset for possible viewport offset changes.
    final Offset startOffset = renderEditable.maxLines == 1
        ? Offset(renderEditable.offset.pixels - _dragStartViewportOffset, 0.0)
        : Offset(0.0, renderEditable.offset.pixels - _dragStartViewportOffset);

    renderEditable.selectPositionAt(
      from: startDetails.globalPosition - startOffset,
      to: updateDetails.globalPosition,
      cause: SelectionChangedCause.drag,
    );
  }

  /// Handler for [TextSelectionGestureDetector.onDragSelectionEnd].
  ///
  /// By default, it services as place holder to enable subclass override.
  ///
  /// See also:
  ///
  ///  * [TextSelectionGestureDetector.onDragSelectionEnd], which triggers this
  ///    callback.
  @protected
  void onDragSelectionEnd(DragEndDetails details) {
    /* Subclass should override this method if needed. */
  }

  /// Returns a [TextSelectionGestureDetector] configured with the handlers
  /// provided by this builder.
  ///
  /// The [child] or its subtree should contain [EditableText].
  Widget buildGestureDetector({
    Key? key,
    HitTestBehavior? behavior,
    required Widget child,
  }) {
    return TextSelectionGestureDetector(
      key: key,
      onTapDown: onTapDown,
      onForcePressStart: delegate.forcePressEnabled ? onForcePressStart : null,
      onForcePressEnd: delegate.forcePressEnabled ? onForcePressEnd : null,
      onSecondaryTap: onSecondaryTap,
      onSecondaryTapDown: onSecondaryTapDown,
      onSingleTapUp: onSingleTapUp,
      onSingleTapCancel: onSingleTapCancel,
      onSingleLongTapStart: onSingleLongTapStart,
      onSingleLongTapMoveUpdate: onSingleLongTapMoveUpdate,
      onSingleLongTapEnd: onSingleLongTapEnd,
      onDoubleTapDown: onDoubleTapDown,
      onDragSelectionStart: onDragSelectionStart,
      onDragSelectionUpdate: onDragSelectionUpdate,
      onDragSelectionEnd: onDragSelectionEnd,
      behavior: behavior,
      child: child,
    );
  }
}