[Bug]: VFX2024 / Qt6: Window Resize Crash Regression after "Fit to First Media loaded"

[williamwira]

What happened?

RV crashing happening with latest main branch (HEAD=518553b12d4b6f7de67b7a648dd7aef611945b7d)

To reproduce:

1. Build OpenRV with Qt 6.5.3 and the rvcfg flag -DRV_VFX_CY2024=1
2. Make sure RV > Preferences > Fit Window to First Media Loaded is active
3. From command line open RV with: rv colorchart,start=1,end=2,width=1920,height=804,fps=24.movieproc
4. After image loads, attempt to resize RV window. RV will crash.

List all the operating systems versions where this is happening

RHEL 9.6

On what computer hardware is this happening?

HP Z8 G4 Workstation, NVIDIA RTX A6000, (40 procs) Intel Xeon Gold 6242R 3.1, 191590MB RAM

Relevant console log output

Totalview shows the crash happening in RV::GLView::event at line 707:

return QOpenGLWidget::event(event);

See attached image for picture of totalview.

Environment variables

No response

Extra information

Code of Conduct

• I agree to follow this project's Code of Conduct

[williamwira]

@bernie-laberge and others -- The issue appears to be related to the QMainWindow::resize step in Qt6 when fitting window to first media loaded.

A few things I came across in my investigation:

The main issues is this: at https://github.com/AcademySoftwareFoundation/OpenRV/blob/main/src/lib/app/RvCommon/RvDocument.cpp#L1282, the resize is running, potentially before something is initialized...? So when manually resizing the window after the resize, that's when the crash happens.

The above resize command is in a block that is only supposed to be run when firstTime is false. But at https://github.com/AcademySoftwareFoundation/OpenRV/blob/main/src/lib/app/RvCommon/GLView.cpp#L370, firstTime is hard-coded to false (even though this should be the first and only time the calling block runs) so we were hitting this case.

When changing the firstTime parameter to true in the GLView call, then there is no crash. But then the resetPolicyTimer runs and shrinks the main window back to its original size, so the resize to first image doesn't visibly happen (see: https://github.com/AcademySoftwareFoundation/OpenRV/blob/main/src/lib/app/RvCommon/RvDocument.cpp#L1289). If we skip the resetPolicyTimer when firstTime is true, then the window behaves mostly correct. The window is manually resizeable, without crashing -- but is locked to only resizing the window larger, and not smaller. I believe that's because at this point the minimum height/width size policies are set to the image size.

As a hack -- I did find at the end of the function, I could add a singleShot to re-run resizeToFit(false, false). This works as whatever needed initialization is apparently initialized. (Though I couldn't explain why, which is troubling.) And then RV behaves as it previously did, as far as I can tell.

So with these changes I've tested, the crash no longer happens, the window resizes to the image correctly, and the window can be resized as expected. However it seems like an egregious hack. Is there a smarter or more intentional way we could handle this, as far as you might be able to see? Thanks in advance!

[williamwira]

Actually -- looks like I can make this much more straightforward. At https://github.com/AcademySoftwareFoundation/OpenRV/blob/main/src/lib/app/RvCommon/GLView.cpp#L370, I can put this block calling resizeToFit(false, false) then center() into a singleShot. That effectively does the same fix I described earlier, without calling the function twice.

I'm guessing this works because the QMainWindow::resize runs after the first paintGL cycle is complete? That's just a guess though. At any rate -- I've put in a pull request with this change. Thanks!

[williamwira]

Update -- I see my change doesn't work with the "preserve aspect while resizing" option. Will pull my PR until I can figure out why.

[williamwira]

Made a new PR that also respects the preserve scaling while resizing option. It's back to what I was originally considering -- calling resizeToFit twice, once in the paintGL handler and then a second time in a single shot so QMainWindow::resize doesn't result in a crashable state.

I did initially want to call the singleshot from the resizeToFit function, but it didn't work -- the singleShot needed to follow the center() function call after resizeToFit.