# how vtkWidgetEvent effect the interaction?

**URL:** <https://discourse.vtk.org/t/how-vtkwidgetevent-effect-the-interaction/15135>\
**Category:** Development\
**Created:** [January 10, 2025, 7:58am UTC](https://discourse.vtk.org/t/how-vtkwidgetevent-effect-the-interaction/15135 "2025-01-10T07:58:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![1727711853](https://discourse.vtk.org/user_avatar/discourse.vtk.org/1727711853/32/8765_2.png) [@1727711853](https://discourse.vtk.org/u/1727711853)\
**Post date:** [January 10, 2025, 7:58am UTC](https://discourse.vtk.org/t/how-vtkwidgetevent-effect-the-interaction/15135/1 "2025-01-10T07:58:13Z")

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when i change the vtkWidgetEvent::Select of “this-\>CallbackMapper-\>SetCallbackMethod(vtkCommand::LeftButtonPressEvent, vtkWidgetEvent::Select, this,EllipseWidget::SelectAction);” to vtkWidgetEvent::AddPoint,my program will occur some strange Phenomenon.but when i see the sourcecode of vtk, i did’nt find any usage of vtkWidgetEvent,they are just to be map to a map[vtkCommand,vtkWidgetEvent],and map the [vtkWidgetEvent,callback function].in this section,i did’nt see the function of vtkWidgetEvent,seem’s remove it and map [vtkCommand,callback function] is a substitute.but then why can’t i change the Select to any other vtkWidgetEvent?how doest it works?thank you.i’ actually confused about it for a long time.