BUG: BackgroundPlotter does not handle HiDPI properly

[pyvista]

BUG: BackgroundPlotter does not handle HiDPI properly

[larsoner]

Just a cross-ref here that we should check if having our own RWI in #149 or moving to PySide6 (or PyQt6 eventually?) magically takes care of this issue.

[larsoner]

I get the same thing on PyQt5 5.12:

And PyQt6:

This suggests that the rendering is still not HiDPI (it should be half the size, or the same size but 2x the resolution) :(

I also get this on mouseover:

>>> Traceback (most recent call last):
  File "/Users/larsoner/python/pyvistaqt/pyvistaqt/rwi.py", line 571, in mouseMoveEvent
    self.__saveX = ev.x()
AttributeError: 'QMouseEvent' object has no attribute 'x'
Abort trap: 6

... so I guess we have more work to do after #149 :)

[larsoner]

... and FYI the upstream issue is https://gitlab.kitware.com/vtk/vtk/-/issues/17953. If we do manage to fix this by messing with rwi.py, we should port the changes upstream to Kitware.

[larsoner]

... since it works on Qt6, I'll close this as wontfix, same as in the upstream https://gitlab.kitware.com/vtk/vtk/-/issues/17953

[larsoner]

Actually it looks like a lot of this should be handled by VTK already:

https://gitlab.kitware.com/vtk/vtk/-/merge_requests/4201/diffs

So I'm confused why it's not for BackgroundPlotter, but is for Plotter. Maybe we need to see if #25 helps by being explicit about parenting or something

[larsoner]

... #25 does not help, but I still think it's useful for cleaning up inheritance

[larsoner]

Actually I suspect the problem might be that BasePlotter and vtkRenderWindowInteractor will both create a RenderWindow (!). I think the solution might be to init BasePlotter first, then pass the self.ren_win it creates to vtkRenderWindowInteractor...

[larsoner]

Okay that's not the problem :(

[larsoner]

Okay I think this might actually be a VTK problem, since the EmbedPyQt example also has this problem:

import sys
import vtk
from PyQt5.QtWidgets import QApplication
from PyQt5.QtWidgets import QMainWindow, QFrame, QVBoxLayout
from vtk.qt.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor

class MainWindow(QMainWindow):

    def __init__(self, parent=None):
        super().__init__(parent)

        self.frame = QFrame(self)
        self.vl = QVBoxLayout()
        self.frame.setLayout(self.vl)
        self.vtkWidget = QVTKRenderWindowInteractor(self.frame)
        self.vl.addWidget(self.vtkWidget)

        self.ren = vtk.vtkRenderer()
        self.vtkWidget.GetRenderWindow().AddRenderer(self.ren)
        self.iren = self.vtkWidget.GetRenderWindow().GetInteractor()

        # Create source
        source = vtk.vtkSphereSource()
        source.SetCenter(0, 0, 0)
        source.SetRadius(5.0)

        # Create a mapper
        mapper = vtk.vtkPolyDataMapper()
        mapper.SetInputConnection(source.GetOutputPort())

        # Create an actor
        actor = vtk.vtkActor()
        actor.SetMapper(mapper)

        self.ren.AddActor(actor)

        self.ren.ResetCamera()

        self.frame.setLayout(self.vl)
        self.setCentralWidget(self.frame)

        self.show()
        self.iren.Initialize()

    def resizeEvent(self, event):
        super().resizeEvent(event)
        print(event.size().width(), event.size().height())
        ren_win = self.vtkWidget.GetRenderWindow()
        print(ren_win.GetSize())
        print(self.ren.GetSize())


if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = MainWindow()
    sys.exit(app.exec_())

The interaction coordinates are wrong, and the rendering is not full-res. I wonder if we should make our own interactor class like Mayavi does...?

Also maybe I should check that embedding a Mayavi scene also works.

[larsoner]

Okay filed an upstream bug:

https://gitlab.kitware.com/vtk/vtk/-/issues/17953

@banesullivan if you can try the two code snippets there on a HiDPI machine and comment over there that it's also a problem for you it might help.

[larsoner]

(mayavi has the same problem, hence why I think it's essentially VTK's problem...)

[larsoner]

Indeed it appears to be a VTK adapter problem, the workaround for now at my end is to use PyQt5 < 5.14

[banesullivan]

Just now looking at this. I can at least reproduce the issue on my laptop

[GuillaumeFavelier]

Well this is encouraging:

Qt 6 supports high-DPI displays on all platforms, and will automatically account for the display resolution when using higher level APIs such as Qt Widgets or Qt Quick. Applications only need to provide high-resolution assets, such as images and icons. The feature is always enabled.

https://doc.qt.io/qt-6/portingguide.html#high-dpi

[larsoner]

FYI @GuillaumeFavelier now that we roll our own QVTKRenderWindowInteractor, we can probably use EDIT: some ideas from #21 to try to fix this. I might take a look today to see if I can get anything sensible working

[larsoner]

This seems to work fine on PySide6 at least, but still not PyQt5. Maybe we can just hope to move to full support for PySide6 (and PyQt6) and just not worry about this at some point...