When saving screenshots, some settings don't take effect

[jromazanov]

I'd like to make a 3D mesh plot, define a camera rotation in the script, show an interactive window with some adjusted settings (e.g. camera rotation, canvas background color), and finally save a screenshot into test.png.

This works fine with pyvista's Plotter class, but apparently not with pyvistaqt's BackgroundPlotter class.
Below is a minimal example. If I run with plotType = 'pv', it works fine, the screenshot has the same rotation and background color as the interactive window. But if I run with plotType = 'pvqt', the screenshot forgets the camera rotation and always uses the same default rotation.

Question: Is there a different way I need to pass the settings and save the screenshot? Or is this a bug?

Expected behavior: (as seen in interactive window)

Actual behavior: (as produced in screenshot)

(Interestingly, other settings are transferred correctly to the pyvistaqt screenshot, e.g. pl.view_yz() would take effect in both interactive window and screenshot.)

import pyvista as pv
import pyvistaqt as pvqt

# uncomment one:
#plotType = 'pv'
plotType = 'pvqt'

# create plotter
if plotType == 'pv':
    pl = pv.Plotter()
else:
    pl = pvqt.BackgroundPlotter()

# do plot
cube = pv.Cube()
pl.add_mesh(cube, show_edges=True)

# change camera angle
pl.camera.azimuth = 45.0

# change background color
pl.set_background('white')

# show figure and take screenshot
if plotType == 'pv':
    pl.show(screenshot='test.png')
else:
    screenshot = pl.screenshot('test.png')
    pl.app.exec_()

[larsoner]

Can you see if some pl.app.processEvents() calls before your pl.screenshot fix things? I'm guessing this is an event-driven problem, assuming what you actually see in the window after / during the app.exec_() is the correct thing (i.e., it is correct but the screenshot is not).

[jromazanov]

Inserting pl.app.processEvents() before pl.screenshot seems to have no effect in my case.
In case it's relevant: I'm running on Ubuntu 22.04 with Python 3.10.6, pyvista 0.37.0, pyvistaqt 0.9.0, OpenGL 4.6, vtk 9.2.2, QtPy 2.0.0 (PyQt5=5.15.2).
And yes, the window / app.exec_() shows the correct thing, but the screenshot doesn't. I've edited the question to include screenshots.

[adeak]

I can repro your issue @jromazanov, and I can even see a brief flash of the wrong render before the final one shows interactively. Adding pl.render() before taking the screenshot fixes it. I don't know what's going on though.

[jromazanov]

Thank you @adeak, I confirm pl.render() fixes it for me!

[josephko91]

I had this exact same issue! pl.render() also worked for me.