Method MouseWheelEvent

Rendering/Context2D/vtkContextTransform.cxx:196–237

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//------------------------------------------------------------------------------
bool vtkContextTransform::MouseWheelEvent(const vtkContextMouseEvent& mouse, int delta)
{
  if (!this->Interactive)
  {
    return vtkAbstractContextItem::MouseButtonPressEvent(mouse);
  }
  if (this->ZoomOnMouseWheel)
  {
    // Determine current position to zoom in on
    vtkVector2d scenePos(mouse.GetScenePos().Cast<double>().GetData());
    vtkVector2d pos(0.0, 0.0);
    vtkTransform2D* transform = this->GetTransform();
    transform->InverseTransformPoints(scenePos.GetData(), pos.GetData(), 1);
    vtkVector2f zoomAnchor = vtkVector2f(pos.Cast<float>().GetData());

    // Ten "wheels" to double/halve zoom level
    float scaling = pow(2.0f, delta / 10.0f);

    // Zoom in on current position
    this->Translate(zoomAnchor[0], zoomAnchor[1]);
    this->Scale(scaling, scaling);
    this->Translate(-zoomAnchor[0], -zoomAnchor[1]);

    // Mark the scene as dirty
    this->Scene->SetDirty(true);

    this->InvokeEvent(vtkCommand::InteractionEvent);
    return true;
  }
  if (this->PanYOnMouseWheel)
  {
    // Ten "wheels" to scroll a screen
    this->Translate(0.0f, delta / 10.0f * this->Scene->GetSceneHeight());

    // Mark the scene as dirty
    this->Scene->SetDirty(true);

    this->InvokeEvent(vtkCommand::InteractionEvent);
    return true;
  }
  return false;
}

//------------------------------------------------------------------------------
void vtkContextTransform::PrintSelf(ostream& os, vtkIndent indent)