SetWidth() and SetHeight() in vtkActor2D causes a crash after a rendering call

Question

I'm trying to overlay text on an image in vtk when a certain button is clicked. I use a vtkTextActor , vtkTextRepresentation , and vtkTextWidget to achieve this.

Here is my code:

// set up actor
textActor->SetInput(label.toStdString().c_str());
textActor->GetTextProperty()->SetColor(1.0, 0.0, 0.0);

// set location of widget
textRepresentation->GetPositionCoordinate()->SetCoordinateSystemToWorld();
textRepresentation->GetPositionCoordinate()->SetValue(200,200);

// set up widget
textWidget->SetInteractor(imageInteractor);
textWidget->SetRepresentation(textRepresentation);
textWidget->SetDefaultRenderer(rend);
textWidget->SetTextActor(textActor);
textWidget->SelectableOff();

// render widget
rend->GetRenderWindow()->Render();
textWidget->On();
textWidget->GetTextActor()->SetWidth(vc[0]);
textWidget->GetTextActor()->SetHeight(vc[1]);
rend->GetRenderWindow()->Render(); // crash

If I comment out the SetWidth and SetHeight function calls, the program works fine and the text widget pops up rather small. However when I try to adjust the width and height of textActor it crashes during the render call. Note that vc[0] and vc[1] are relative to the viewport coordinate system, I calculate them in a different function.

I can adjust the width and height of textActor BEFORE the textWidget->On() call, and the widget will still pop up, but it ignores my width and height changes. I cannot seem to change the box dimensions programatically. Am I doing something wrong or is this a vtk bug?

Here is an example. I'd like the text to appear bigger (changing the font size wont work, I think its because the actor itself is too small).

UPDATE I have not figured out why its crashing or how to fix it. As a workaround, I've been adjusting the Position2Coordinate value in my textRepresentation . The rendering call seems to be readjusting my set values. Can anyone explain why or how to fix this?

Answer 1

I'm not sure what's causing the crash, but I found a workaround. By using textRepresentation->SetPosition(x1,x2) and textRepresentation->SetPosition2(width,height) , I'm able to control the location and size of the widget. Its important to note that SetPosition2() is relative to SetPosition() meaning instead of a coordinate, the second position should be thought of a width and height. All of my values are in the Normalized Viewport coordinate system.