Reimplement Qt3DWindow to work with Qt Webengine

[jbp35]

This is a follow-up of: #47873

Qt3DWindow is currently not compatible with Qt Webengine. As mentioned in QT doc, when using Qt::AA_ShareOpenGLContexts (which is required for Qt Webengine) it is strongly recommended to set the default QSurface format before the construction of the Qapplication. Otherwise, the format will not be applied to the global share context and therefore issues may arise with context sharing afterwards.

https://doc.qt.io/qt-6/qsurfaceformat.html#setDefaultFormat

However, Qt3DWindow sets the default QSurface format during its initialization which is causing the following warning message:

This PR is a tentative to work around this issue by reimplementing Qt3dWindow. The new implementation lets qgis main.cpp configure the default Qsurface format.

Added benefit of this approach is that it should also make it possible to overlay widgets on top of the 3d viewport which is currently not possible using Qt3dWindow.

[wonder-sk]

Hi @jbp35 - thanks for the pull request! I have been looking into these issues in the last couple of days, and I am have been heading towards a similar solution but I am still testing various options. I have left a couple of comments.

Also a bunch of general questions:

• what operating system(s) have you been testing on?
• what Qt versions have you tried? Qt5 only, or also Qt6?
• what do you test to verify the PR has fixed the issues? (e.g. open a qgis 3d window, then open a webengine window, and they both work with no crash?)

Are you doing this to get PyQt5.QtWebEngineWidgets working? Because for me, with similar implementation, import of this PyQt5 module would still fail with an import error:

QtWebEngineWidgets must be imported before a QCoreApplication instance is created

And it seems that getting this python module working may be a bit more tricky, because in QGIS, python gets initialized much later than when QApplication gets instantiated.

[jbp35]

Hi, thanks for the comments! Regarding testing, I just wanted to share the overall approach before to spend too much time on it, so there is still a lot more to be done. I only tested on windows with QT5 so far, using a python script to create a QT WebEngine window.

In order to get PyQt5.QtWebEngineWidgets to work, you have to update manually PyQtWebEngine (only version 5.15.6 will work). This version does not exit if shared opengl context is enabled.
You may also have to upgrade python3-pyqt5-sip if you get another error message “RuntimeError: the sip module implements API v12.0 to v12.8 but the PyQt5.QtCore module requires API v12.9” after upgrading PyQtWebEngine.

Here is the python script I am using to create the QtWebEngine window:

from PyQt5.QtWebEngineWidgets import QWebEngineView
from qgis.PyQt import QtWidgets
from qgis.PyQt.QtCore import QUrl

dlg = QtWidgets.QDialog()
view = QWebEngineView()
layout = QtWidgets.QHBoxLayout()
layout.setContentsMargins(0, 0, 0, 0)
layout.addWidget(view)
dlg.setLayout(layout)

url = QUrl("https://www.whatsmybrowser.org/")
view.load(url)
view.show()

dlg.show()

[wonder-sk]

Regarding testing, I just wanted to share the overall approach before to spend too much time on it, so there is still a lot more to be done.

Ah ok, cool! The overall approach seems fine to me, so yeah, let's try to address the ugly details :-)

In order to get PyQt5.QtWebEngineWidgets to work, you have to update manually PyQtWebEngine (only version 5.15.6 will work). This version does not exit if shared opengl context is enabled.

I see... I am on ubuntu 22.04, and I can see now that my python3-pyqt5 is at 5.15.6, but python3-pyqt5.qtwebengine is versioned separately and it is at 5.15.5. And indeed, there should be a fix related to AA_ShareOpenGLContexts in the latest version. Great to see this got addressed.

For the time being I will stick to the existing PyQt5.QtWebEngineWidgets from my system, and use C++ code to test QtWebEngine inside QGIS... I am mainly concerned about having QGIS 3D running smoothly, even if QtWebEngine is used (for Qt6 we will probably need to move to QtWebEngine and finally ditch QtWebKit)

[github-actions]

🪟 Windows builds ready!

Windows builds of this PR are available for testing here. Debug symbols for this build are available here.

(Built from commit 8952595)

[github-actions]

Tests failed for Qt 6

One or more tests failed using the build from commit db47e93

pointcloud_3d_singlecolor (testPointCloudSingleColor)

pointcloud_3d_singlecolor

Test failed at testPointCloudSingleColor at tests/src/3d/testqgspointcloud3drendering.cpp:272

• Rendered image did not match tests/testdata/control_images/3d/expected_pointcloud_3d_singlecolor/default/expected_pointcloud_3d_singlecolor.png (found 19054 pixels different)
• Rendered image did not match tests/testdata/control_images/3d/expected_pointcloud_3d_singlecolor/qt6/expected_pointcloud_3d_singlecolor.png (found 68 pixels different)

pointcloud_3d_colorramp (testPointCloudAttributeByRamp)

pointcloud_3d_colorramp

Test failed at testPointCloudAttributeByRamp at tests/src/3d/testqgspointcloud3drendering.cpp:312

• Rendered image did not match tests/testdata/control_images/3d/expected_pointcloud_3d_colorramp/default/expected_pointcloud_3d_colorramp.png (found 25444 pixels different)
• Rendered image did not match tests/testdata/control_images/3d/expected_pointcloud_3d_colorramp/qt6/expected_pointcloud_3d_colorramp.png (found 71 pixels different)

pointcloud_3d_classification (testPointCloudClassification)

pointcloud_3d_classification

Test failed at testPointCloudClassification at tests/src/3d/testqgspointcloud3drendering.cpp:349

• Rendered image did not match tests/testdata/control_images/3d/expected_pointcloud_3d_classification/default/expected_pointcloud_3d_classification.png (found 24782 pixels different)
• Rendered image did not match tests/testdata/control_images/3d/expected_pointcloud_3d_classification/qt6/expected_pointcloud_3d_classification.png (found 68 pixels different)

The full test report (included comparison of rendered vs expected images) can be found here.

Further documentation on the QGIS test infrastructure can be found in the Developer's Guide.

[wonder-sk]

Finally managed to test this with both Qt5 and Qt6 on linux - and I can confirm things seems to be working fine even if there is a qt3d window and webengine window displayed at the same time, and without any scary warnings/errors from Qt. Well done @jbp35 and sorry for the long delay from me!

I have added some minor sip and test fixes on the branch, and if all tests pass I think we should be good to merge this.

[jbp35]

Finally managed to test this with both Qt5 and Qt6 on linux - and I can confirm things seems to be working fine even if there is a qt3d window and webengine window displayed at the same time, and without any scary warnings/errors from Qt. Well done @jbp35 and sorry for the long delay from me!

I have added some minor sip and test fixes on the branch, and if all tests pass I think we should be good to merge this.

@wonder-sk Thank you for the review!

One doubt on my side, should we also bump dependencies for PyQtWebEngine (>= 5.15.6) and python3-pyqt5-sip (>=12.9) to avoid that users get an error when trying to run a plugin using QtWebEngineWidgets?

[wonder-sk]

I will try to add a summary of things here:

• Qt WebEngine needs QtWebEngine::initialize() to be called before QApplication is created - what it really does is that it sets Qt::AA_ShareOpenGLContexts
• that flag was added in set Qt::AA_ShareOpenGLContexts on all platforms #47873 to allow plugins to use WebEngine from PyQt, but then soon afterwards reverted in Disable shared opengl contexts #49888 because it does not play well with existing Qt 3D code. User could get ugly warnings (Warning: Setting a new default format with a different version or profile after the global shared context is created may cause issues with context sharing.) and/or crashes (?)
• the problem here is that Qt3DWindow constructor calls QSurfaceFormat::setDefaultFormat() which triggers the warning and potentially causes further issues - there is QTBUG-60614 about that, but not much happened towards its resolution
• the solution is to:
  1. set default QSurfaceFormat in a way that both WebEngine and QGIS 3D are happy
  2. enable shared opengl contexts
  3. create QApplication and then do not change anything anymore related to surface format
• we need to replace Qt3DWindow by a custom QWindow implementation that does not call QSurfaceFormat::setDefaultFormat() and simply uses whatever default format has been set - fortunately this is not a lot of code - the new Qgs3DWindow class does that for us
• we need to pick some "global" OpenGL version... Understanding all the OpenGL versions, profiles, their support on different systems and various forward/backward compatibility issues is a bit of nightmare (at least for me)
  • it looks like WebEngine needs OpenGL 3.2 Core profile, but it can live with higher OpenGL version too
  • QGIS 3D does not have requirements for a very recent OpenGL version - Qt3DWindow would ask for 4.3 Core profile.
  • on Mac, Apple stopped supporting newer OpenGL version longer time ago, it is stuck at 4.1 Core (https://support.apple.com/en-us/101525)
  • in the end, we set surface format to OpenGL 4.3, and 4.1 on Mac

Sorry if some bits are not 100% correct - there are various things here I do not fully understand (OpenGL contexts + their sharing in Qt apps, WebEngine / Qt3D specifics of how OpenGL contexts are used).

[wonder-sk]

One doubt on my side, should we also bump dependencies for PyQtWebEngine (>= 5.15.6) and python3-pyqt5-sip (>=12.9) to avoid that users get an error when trying to run a plugin using QtWebEngineWidgets?

@jbp35 I have not really looked into that, I was primarily concerned about getting things work on C++ side of things. If there are some bumps of dependencies needed, that's something to sort out with QGIS packagers. Do you have some reference to what got fixed in those package versions?

[jbp35]

One doubt on my side, should we also bump dependencies for PyQtWebEngine (>= 5.15.6) and python3-pyqt5-sip (>=12.9) to avoid that users get an error when trying to run a plugin using QtWebEngineWidgets?

@jbp35 I have not really looked into that, I was primarily concerned about getting things work on C++ side of things. If there are some bumps of dependencies needed, that's something to sort out with QGIS packagers. Do you have some reference to what got fixed in those package versions?

PyQt5-WebEngine >= 5.15.6
Here is the explanation for the need to bump the dependency :
#49512 (comment)

This is needed for QtWebEngineWidgets to work using python.

PyQt6-WebEngine >= 6.2-maint
This would also need to be done for PyQt6-WebEngine (minimum version 6.2-maint)

Changelog for PyQt6:
https://www.riverbankcomputing.com/static/Downloads/PyQt6-WebEngine/ChangeLog-6.6.0.dev2310250952

2022-03-15  Phil Thompson  <phil@riverbankcomputing.com>
NEWS, PyQt6-WebEngine.msp:
Allow Qt.AA_ShareOpenGLContexts to be specified before a
QCoreApplication is created to allow QtWebEngineWidgets to be
imported later.
[060f78886515] <6.2-maint>

This is needed for QtWebEngineWidgets to work using python.

python3-pyqt5-sip >=12.9

I am not so sure that this is needed - it may just be that I was importing from PyQt5 instead of qgis.PyQt in my script above but I am not able to test this right now.

[wonder-sk]

I'm still not sure if I understand why PyQt5-WebEngine needs to be upgraded... with this PR, AA_ShareOpenGLContexts flag gets set before QApplication is created... so isn't that issue solved already?

[jbp35]

I'm still not sure if I understand why PyQt5-WebEngine needs to be upgraded... with this PR, AA_ShareOpenGLContexts flag gets set before QApplication is created... so isn't that issue solved already?

When using WebEngine with python, PyQt5-WebEngine is intialized after the creation of QgsApplication.

In old versions, PyQt5-WebEngine checks if a QApplication already exists during initialization and throw an error even if `AA_ShareOpenGLContexts' is enabled.

In versions >= 5.16.6, it does not throw an error if `AA_ShareOpenGLContexts' is enabled and continue initialisation.

[jbp35]

I will try to add a summary of things here:

• Qt WebEngine needs QtWebEngine::initialize() to be called before QApplication is created - what it really does is that it sets Qt::AA_ShareOpenGLContexts

• that flag was added in set Qt::AA_ShareOpenGLContexts on all platforms #47873 to allow plugins to use WebEngine from PyQt, but then soon afterwards reverted in Disable shared opengl contexts #49888 because it does not play well with existing Qt 3D code. User could get ugly warnings (Warning: Setting a new default format with a different version or profile after the global shared context is created may cause issues with context sharing.) and/or crashes (?)

• the problem here is that Qt3DWindow constructor calls QSurfaceFormat::setDefaultFormat() which triggers the warning and potentially causes further issues - there is QTBUG-60614 about that, but not much happened towards its resolution

• the solution is to:

  1. set default QSurfaceFormat in a way that both WebEngine and QGIS 3D are happy
  2. enable shared opengl contexts
  3. create QApplication and then do not change anything anymore related to surface format

• we need to replace Qt3DWindow by a custom QWindow implementation that does not call QSurfaceFormat::setDefaultFormat() and simply uses whatever default format has been set - fortunately this is not a lot of code - the new Qgs3DWindow class does that for us

• we need to pick some "global" OpenGL version... Understanding all the OpenGL versions, profiles, their support on different systems and various forward/backward compatibility issues is a bit of nightmare (at least for me)

  • it looks like WebEngine needs OpenGL 3.2 Core profile, but it can live with higher OpenGL version too
  • QGIS 3D does not have requirements for a very recent OpenGL version - Qt3DWindow would ask for 4.3 Core profile.
  • on Mac, Apple stopped supporting newer OpenGL version longer time ago, it is stuck at 4.1 Core (https://support.apple.com/en-us/101525)
  • in the end, we set surface format to OpenGL 4.3, and 4.1 on Mac

Sorry if some bits are not 100% correct - there are various things here I do not fully understand (OpenGL contexts + their sharing in Qt apps, WebEngine / Qt3D specifics of how OpenGL contexts are used).

This is a good summary.

Regarding https://bugreports.qt.io/browse/QTBUG-60614, I think the logic is that Qt3DWindow is just a helper class to get started quickly with qt 3d (part of QT 3d Extras) and that it is meant to be reimplemented to suit project needs.. it is therefore unlikely that they will ever fix this and writing a custom class is the way to go.

[wonder-sk]

In old versions, PyQt5-WebEngine checks if a QApplication already exists during initialization and throw an error even if `AA_ShareOpenGLContexts' is enabled.

In versions >= 5.16.6, it does not throw an error if `AA_ShareOpenGLContexts' is enabled and continue initialisation.

Ah ok, that makes sense - thanks for the clarification!

To get the python packages upgraded, you will probably need to get in touch with package maintainers for various platform and ask them to do the upgrade - unfortunately there is no "official" registry of what package versions should be used with qgis installers...

[jbp35]

In old versions, PyQt5-WebEngine checks if a QApplication already exists during initialization and throw an error even if AA_ShareOpenGLContexts' is enabled. In versions >= 5.16.6, it does not throw an error if AA_ShareOpenGLContexts' is enabled and continue initialisation.

Ah ok, that makes sense - thanks for the clarification!

To get the python packages upgraded, you will probably need to get in touch with package maintainers for various platform and ask them to do the upgrade - unfortunately there is no "official" registry of what package versions should be used with qgis installers...

Alright, for reference I already opened a ticket for osgeo4W a few months ago:
https://trac.osgeo.org/osgeo4w/ticket/788