onTapDown method

Implementation

@protected
void onTapDown(TapDragDownDetails details) {
  if (!delegate.selectionEnabled) {
    return;
  }

  // TODO(Renzo-Olivares): Migrate text selection gestures away from saving state
  // in renderEditable. The gesture callbacks can use the details objects directly
  // in callbacks variants that provide them [TapGestureRecognizer.onSecondaryTap]
  // vs [TapGestureRecognizer.onSecondaryTapUp] instead of having to track state in
  // renderEditable. When this migration is complete we should remove this hack.
  // See https://github.com/flutter/flutter/issues/115130.
  renderEditable.handleTapDown(TapDownDetails(globalPosition: details.globalPosition));
  // 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;
  // TODO(justinmc): Should a desktop platform show its selection toolbar when
  // receiving a tap event?  Say a Windows device with a touchscreen.
  // https://github.com/flutter/flutter/issues/106586
  _shouldShowSelectionToolbar =
      kind == null || kind == PointerDeviceKind.touch || kind == PointerDeviceKind.stylus;

  // It is impossible to extend the selection when the shift key is pressed, if the
  // renderEditable.selection is invalid.
  final bool isShiftPressedValid =
      _isShiftPressed && renderEditable.selection?.baseOffset != null;
  switch (defaultTargetPlatform) {
    case TargetPlatform.android:
      if (editableText.widget.stylusHandwritingEnabled) {
        final bool stylusEnabled = switch (kind) {
          PointerDeviceKind.stylus ||
          PointerDeviceKind.invertedStylus => editableText.widget.stylusHandwritingEnabled,
          _ => false,
        };
        if (stylusEnabled) {
          Scribe.isFeatureAvailable().then((bool isAvailable) {
            if (isAvailable) {
              renderEditable.selectPosition(cause: SelectionChangedCause.scribble);
              Scribe.startStylusHandwriting();
            }
          });
        }
      }
    case TargetPlatform.fuchsia:
    case TargetPlatform.iOS:
      // On mobile platforms the selection is set on tap up.
      break;
    case TargetPlatform.macOS:
      editableText.hideToolbar();
      // On macOS, a shift-tapped unfocused field expands from 0, not from the
      // previous selection.
      if (isShiftPressedValid) {
        final TextSelection? fromSelection =
            renderEditable.hasFocus ? null : const TextSelection.collapsed(offset: 0);
        _expandSelection(details.globalPosition, SelectionChangedCause.tap, fromSelection);
        return;
      }
      // On macOS, a tap/click places the selection in a precise position.
      // This differs from iOS/iPadOS, where if the gesture is done by a touch
      // then the selection moves to the closest word edge, instead of a
      // precise position.
      renderEditable.selectPosition(cause: SelectionChangedCause.tap);
    case TargetPlatform.linux:
    case TargetPlatform.windows:
      editableText.hideToolbar();
      if (isShiftPressedValid) {
        _extendSelection(details.globalPosition, SelectionChangedCause.tap);
        return;
      }
      renderEditable.selectPosition(cause: SelectionChangedCause.tap);
  }
}