Viewer just opens a black screen.

[MacDougal]

Since updating graphic drivers to AMD Adrenalin 24.9.1 (WHQL), the Calibre book viewer simply shows a black window. No UI elements are drawn. The book is still there (it can be copy/pasted, things can be dragged, and even the button strip can be pulled out where it becomes visible). This happens with all versions of Calibre back to version 7.12, and affects the book editor, pointing to an issue with the QT Webengine and graphics driver.

I've tried adding the "QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu" environment variable, but it simply does nothing to calibre's GPU usage, so presumably is not disabling GPU acceleration on the QT Webengine and the black window persists.

The only thing that seems to fix the issue is going back to an older video driver 24.7.1, or booting into safe mode (which would also disable the driver's acceleration.

Does anyone have any fixes to disable GPU acceleration in calibre's QT Webengine, or any way to get things working again with the current drivers? Any settings in Calibre that I can use?

[kovidgoyal]

That environemnt variable is the only setting and it works fine, reboot after setting it to make sure it applies.

[MacDougal]

Is this the environment setting you are talking about? Because this gives me a black screen as shown (I've managed to blindly pull out the control strip, if I drag it back into the window it will disappear).

The window itself resizes slowly as if the window is not accelerated, but if I put the mouse where the text should be and scroll, I can see GPU activity spike. Is the contents of the window still using GPU acceleration where the window itself if not? Should the system variable set be a user variable? Does the variable only work if QT Webeingine is set into debug mode?

Thanks for any help or ideas you can suggest.

[JSWolf]

Originally Posted by MacDougal

Is this the environment setting you are talking about? Because this gives me a black screen as shown (I've managed to blindly pull out the control strip, if I drag it back into the window it will disappear).

The window itself resizes slowly as if the window is not accelerated, but if I put the mouse where the text should be and scroll, I can see GPU activity spike. Is the contents of the window still using GPU acceleration where the window itself if not? Should the system variable set be a user variable? Does the variable only work if QT Webeingine is set into debug mode?

Thanks for any help or ideas you can suggest.

Did you reboot?

[kovidgoyal]

That's correct and it works in all Qt modes, not just debug. As for its effects only the Qt developers can tell you in detail what it does. If it isn't resolving the issue for you then stick with the downgraded video drivers. You might also get some useful debug output from qt by running the viewer in a command prompt as

calibre-debug -w

[MacDougal]

Originally Posted by JSWolf

Did you reboot?

Yes, hence my confusion as to why it isn't working. I did some googling before posting and this seems to have been an ongoing issue going back years that people have experienced in many different configurations. For some reason QT wbengine sometimes just doesn't play nice with GPUs.

[JSWolf]

Originally Posted by MacDougal

Yes, hence my confusion as to why it isn't working. I did some googling before posting and this seems to have been an ongoing issue going back years that people have experienced in many different configurations. For some reason QT wbengine sometimes just doesn't play nice with GPUs.

Are you using a laptop with dual-GPUs? if so, have calibre run with the other GPU.

[MacDougal]

Originally Posted by kovidgoyal

That's correct and it works in all Qt modes, not just debug. As for its effects only the Qt developers can tell you in detail what it does. If it isn't resolving the issue for you then stick with the downgraded video drivers. You might also get some useful debug output from qt by running the viewer in a command prompt as

calibre-debug -w

Here's the output (with the environment variable set) if that any use to you. It still creates a black window as above:

C:\Program Files\Calibre2>calibre-debug -w
QPA platform: windows
devicePixelRatio: 1.0
logicalDpi: 96.0 x 96.0
physicalDpi: 81.55183946488295 x 81.64285714285714
ApplicationPaletteChange event ignored
Using calibre Qt style: True
Sandboxing disabled by user.
[2.140] bridge ready
[2.281] iframe ready
[0.000] Load of book started
[0.000] prepared emitted
[0.062] webview loading requested
[0.187] loading finished

I have also reported this to AMD as a bug so they can investigate the issue at their end.

[MacDougal]

Originally Posted by JSWolf

Are you using a laptop with dual-GPUs? if so, have calibre run with the other GPU.

Nope, desktop with one GPU.

[MacDougal]

I finally found a solution. These are the environment variables that need to be set:

QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu
QT_QUICK_BACKEND=software

Hopes this help anyone else who needs to disable GPU rendering for a driver issue.

[MacDougal]

If this breaks the AMD Adrenaline driver UI (which seems to also use QTWebEngine), you need to do it as a batch file so it runs in it's own environment. Just copy the following into a text file named "Calibre.bat" on your desktop.

@echo off
set QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu
set QT_QUICK_BACKEND=software
start "" "C:\Program Files\Calibre2\calibre.exe"

Click on this to run Calibre instead of the normal Calibre icon on your desktop.

[DiapDealer]

Originally Posted by MacDougal

QT_QUICK_BACKEND=software

I have great luck with QT_QUICK_BACKEND=software on Linux systems with proprietary nvidia drivers (and Qt6.8+). It makes QWebEngine rendering on my system (which is not underpowered in the least) positively snappy again. It also gets rid of the annoying "driver does not support GBM" warning. But I don't have to use QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu in that situation. It renders fine--it's just sluggish.

On Windows, I find that QT_QUICK_BACKEND=software shifts any and all GPU QWebEngine hardware usage to the CPU regardless of whether QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu is set or not.