receivedPointerSignal method

@protected void receivedPointerSignal(PointerSignalEvent event)

Handle mousewheel and web trackpad scroll events.

Implementation

@protected
void receivedPointerSignal(PointerSignalEvent event) {
  final double scaleChange;
  if (event is PointerScrollEvent) {
    if (!_ctrlPressed) {
      // Normal scroll, so treat it as a pan.
      if (!gestureIsSupported(GestureType.pan)) {
        return;
      }

      Offset scrollDelta = event.scrollDelta;
      //TODO add axis alignement
      if (event.kind == PointerDeviceKind.trackpad) {
        if (scrollDelta.dx != 0) {
          scrollbarController?.onScrollStartHorizontal();
        }
        if (scrollDelta.dy != 0) {
          scrollbarController?.onScrollStartVertical();
        }
      } else {
        //Shift pressed, so scroll horizontally with the mousewheel
        if (_shiftPressed) {
          scrollDelta = Offset(scrollDelta.dy, scrollDelta.dx);
          scrollbarController?.onScrollStartHorizontal();
        } else {
          scrollbarController?.onScrollStartVertical();
        }
      }

      final Offset localDelta = PointerEvent.transformDeltaViaPositions(
        untransformedEndPosition: event.position + scrollDelta,
        untransformedDelta: scrollDelta,
        transform: event.transform,
      );

      final Offset focalPointScene = transformationController!.toScene(
        event.localPosition,
      );

      final Offset newFocalPointScene = transformationController!.toScene(
        event.localPosition - localDelta,
      );

      transformationController!.value = matrixTranslate(
          transformationController!.value,
          newFocalPointScene - focalPointScene);
      scrollbarController?.onScrollEnd();
      return;
    }
    // Ignore left and right mouse wheel scroll.
    if (event.scrollDelta.dy == 0.0) {
      return;
    }
    scaleChange = math.exp(-event.scrollDelta.dy / widget.scaleFactor);
  } else if (event is PointerScaleEvent) {
    scaleChange = event.scale;
  } else {
    return;
  }

  if (!gestureIsSupported(GestureType.scale)) {
    return;
  }
  scrollbarController?.onScrollStart();

  final Offset focalPointScene = transformationController!.toScene(
    event.localPosition,
  );

  transformationController!.value = matrixScale(
    transformationController!.value,
    scaleChange,
  );

  // After scaling, translate such that the event's position is at the
  // same scene point before and after the scale.
  final Offset focalPointSceneScaled = transformationController!.toScene(
    event.localPosition,
  );
  transformationController!.value = matrixTranslate(
    transformationController!.value,
    focalPointSceneScaled - focalPointScene,
  );

  afterZoom();
  scrollbarController?.onScrollEnd();
}