Issue with Calibre Viewer

[RbnJrg]

I'm using the last version of Calibre Portable and I'm running Windows 7 Ultimate 64 bits. When I want to open the epub I attach, I get the following output with Calibre Viewer:



I don't know what may be wrong. I would appreciate any answer that allow me to solve the issue.

Thanks in advance.
Rubén

[BetterRed]

The book is OK on calibre 4.17 on Windows 10 1909.

Is it only that book that's not working, or all epubs?

What version of calibre were you using before?

There are video driver related issues with the version of Qt used in calibre 4.nn, particularly on Windows 7 and some Linux systems. You could try updating your video drivers.

BR

[kovidgoyal]

That's a video driver issue. Note that windows 7 is not supported with calibre 4 precisely for this issue. You can try various workrounds:

1) Update your video drivers
2) Turn off hardware acceleration https://doc.qt.io/qt-5/qtwebengine-debugging.html
3) Stay with calibre 3.48 till you are able to move off windows 7

[RbnJrg]

Originally Posted by kovidgoyal

That's a video driver issue. Note that windows 7 is not supported with calibre 4 precisely for this issue. You can try various workrounds:

1) Update your video drivers
2) Turn off hardware acceleration https://doc.qt.io/qt-5/qtwebengine-debugging.html
3) Stay with calibre 3.48 till you are able to move off windows 7

Many thanks. My video drivers are updated and turn off hardware acceleration by setting the environment variable

QTWEBENGINE_CHROMIUM_FLAGS="--disable-gpu" calibre-viewer

seems not to have any effect. The curious thing is that when the Viewer is able to display an epub correctly, then all epubs can be displayed, even those ones that wasn't able to at a first moment. I don't know why some epubs are showed without issues and others didn't.

[BetterRed]

Originally Posted by RbnJrg

<snip>

The curious thing is that when the Viewer is able to display an epub correctly, then all epubs can be displayed, even those ones that wasn't able to at a first moment. I don't know why some epubs are showed without issues and others didn't.

Hmmm - that suggests it may not be a video driver issue.

The posts (starting at #12) between myself and the OP (Harakane) in this thread may offer a solution ==>> [Help] Calibre 4.X eBook Viewer Broken.

BR

[RbnJrg]

Originally Posted by BetterRed

Hmmm - that suggests it may not be a video driver issue.

The posts (starting at #12) between myself and the OP (Harakane) in this thread may offer a solution ==>> [Help] Calibre 4.X eBook Viewer Broken.

BR

Thanks for your answer. Indeed, it's not a video driver issue. As I said before, I use the portable version of Calibre but after reading your post, I tried the 64bit version of Calibre (non-portable). Well, the Viewer works flawlessly; not a single display error. So, there is a difference between the viewer that comes with the portable version and the 64bit one. Maybe a bug, I don't know.

[BetterRed]

Originally Posted by RbnJrg

Thanks for your answer. Indeed, it's not a video driver issue. As I said before, I use the portable version of Calibre but after reading your post, I tried the 64bit version of Calibre (non-portable). Well, the Viewer works flawlessly; not a single display error. So, there is a difference between the viewer that comes with the portable version and the 64bit one. Maybe a bug, I don't know.

The other report started with the problem in 64 bit, a reinstall did not fix it, but the viewer was OK in a fresh portable. So, the OP removed the 64 bit AND all the configuration data and calibre related registry entries and then installed a fresh 64 bit and that was OK too.

I have emphasised 'fresh' because I suspect its something in the configuration data getting corrupted in a way that that the code hasn't anticipated.

If you still have the portable install:

• With calibre not running, rename <wherever>\Calibre Settings\viewer-webengine.json to something like <wherever>\Calibre Settings\viewer-webengine.save.
• Then start calibre portable and try read that Lucio Apuleyo EPUB.
• And let us know what happens.

BR

[RbnJrg]

Originally Posted by BetterRed

If you still have the portable install:

• With calibre not running, rename <wherever>\Calibre Settings\viewer-webengine.json to something like <wherever>\Calibre Settings\viewer-webengine.save.
• Then start calibre portable and try read that Lucio Apuleyo EPUB.
• And let us know what happens.

BR

Many thanks for your help BR. I did what you said and the issue remains I think is something related with the 32bit compilation that is not working properly in a 64bit system. What a pity that Kobid doesn't release a 64bit portable version; if it were so, we would be able to conclude if the issue is due to that or not.

[BetterRed]

One more thing you could try on the portable install:

• You will lose your customisations, plugins etc, so you might want to take a backup first
• With calibre not running, delete the folder <wherever>\Calibre Settings
• Then start calibre portable, it will create a fresh Calibre Settings. Then try viewing that Lucio Apuleyo EPUB.
• And let us know what happens.

If that doesn't work I'm baffled, bewildered, and out of ideas.

BR

[RbnJrg]

Originally Posted by BetterRed

One more thing you could try on the portable install:

• You will lose your customisations, plugins etc, so you might want to take a backup first
• With calibre not running, delete the folder <wherever>\Calibre Settings
• Then start calibre portable, it will create a fresh Calibre Settings. Then try viewing that Lucio Apuleyo EPUB.
• And let us know what happens.

If that doesn't work I'm baffled, bewildered, and out of ideas.

BR

Well, I have good news and bad news. The good news is that now I can use the Calibre Viewer without issues with all epubs INSIDE Calibre. The bad news is that the issue remains when I use Calibre Viewer to open epubs OUTSIDE Calibre.

To test the rendering RMSDK engine I use ADE; but to test WebKit I use PocketBook in Android and Calibre Viewer to test epubs on PCs. I had discovered that Calibre Viewer could be used without starting Calibre Manager and without loading the ebook in the Calibre Library but for this last task I still can't use reliably the viewer (at least, with the portable version) because some epubs can not be displayed without using Calibre Manager.

But one thing at least is solved Thanks for your help BR.

Rubén