Head's up for those that build Sigil from source - Page 4

DiapDealer · 10-10-2026, 06:51 PM

Quote:

Originally Posted by KevinH

Could the Windows build for both avif and jxl plugins be turning off something Windows needs in libjxl or libavif?

When they built, I just assumed they were OK. They seem fine for "normal" sized images. And others seem to be experiencing much better performance than I am on their windows machines with this monster epub. My ancient Windows 10 laptop was slow, but both it and my Windows VM handle that epub better than this much newer Windows 11 machine with gaming graphics and tons of ram/cpu. *Shrug*

Quote:

Originally Posted by KevinH

It is wild that turning off the gpu acceleration actually speeds things up!

I know. That makes no sense to me!

DiapDealer · 10-11-2026, 08:45 AM

I've seen several reports that jxl is engineered for high-efficiency encoding and decoding directly on the CPU across mobile and desktop devices without needing specialized hardware support. In fact: Disabling hardware acceleration in Chrome forces the browser to rely on software rendering through the CPU rather than offloading tasks to the GPU. If a GPU driver is buggy, outdated, or poorly optimized for a specific image rasterization path, falling back to CPU software rendering can eliminate lag or stutter.

This has definitely been my experience with the huge jxl images (as well as avif) on multiple Windows machines. A tired Windows 10 laptop, a beefy Windows 11 gaming desktop, a Windows 11 qemu vm on a stout Linux host, and a newer high-end Windows 11 mini-pc.

The speedup on jxls when disabling gpu hardware acceleration still doesn't make sense since Preview is converting them on the fly to jpg (95%). The only explanation is that large jpgs benefit from using software rendering in chrome on Windows as well.

I believe I'm going to start disabling WebEngine's GPU acceleration by default on Windows from now on.

KevinH · 10-11-2026, 09:52 AM

I also thought about that. I think Calibre disables it as well fwiw.

DiapDealer · 10-11-2026, 12:26 PM

My Windows 11 Mini-PC holds its own with the monster-sized images fairly well (after disabling acceleration, excluding all of Sigil's binaries/folders from antivirus, and telling Windows to optimize performance for Sigil and QtWebEngineProcess), so I think I'm ready to put this test case to bed. If you want to use monster-sized avifs in your epubs on Windows, be prepared for some fairly sluggish Sigil performance regardless of your hardware.

KevinH · 10-11-2026, 01:11 PM

Curious... How do you actually tell Windows to optimize performance for Sigil and QtWebEngineProcess? Is this akin to changing scheduling priority for specific processes on Linux?

DiapDealer · 10-11-2026, 01:29 PM

Quote:

Originally Posted by KevinH

Curious... How do you actually tell Windows to optimize performance for Sigil and QtWebEngineProcess? Is this akin to changing scheduling priority for specific processes on Linux?

It's mostly a graphics thing. You can let Windows decide how to handle things, or you can choose a power saving option or a high performance option.

KevinH · 10-11-2026, 01:54 PM

FYI, disabling the GPU on my arm64 M2 Max using Sigil preferences and restarting Sigil, sped up loading avif slightly. So it is not just a Windows thing.

DiapDealer · 10-12-2026, 02:02 PM

Good to know. The bottom line here is that our plugins are working fine in image resources tabs. And as you already mentioned, we can't really help Preview (QtWebEngine) load anything any faster. Except recommending disabling acceleration, and rendering jxls as 95% jpgs, it's out of our hands.

KevinH · 10-16-2026, 10:12 AM

Hi All,

I think I am done farting around with the future Sigil 2.8.5 unless something is broken.

Except for forthcoming updated translations, I have hopefully pushed the last change.

The upcoming 2.8.5 release actually includes a huge number of changes, bug fixes, and new features including a complete overhaul of the css parser used inside Sigil which should help keep Sigil up to date when it comes to CSS selectors for at least a little bit.

It also completely changes the internals of all our singleton classes to be safer. New image formats were added (avif, jxl), updated image editing, new custom special characters, etc, etc., etc.

In hindsight this probably should have been named Sigil 2.9.5 or even Sigil 3.0.0 but ... we can save 3.0 for when we next update to the latest Qt, latest Python, latest lexbor, latest pcre2, etc.

In all my testing, it has been really stable, but of course there still could be issues that I have just not triggered given how I use Sigil.

So please build from master and start using it on a normal basis and let me know if you run into any difficulties.

Updated, hopefully final, translations should be coming in just over a week or two (to give translators time to make any changes they want).

Thank you.

Once we get final translations, if needed we can create a public release candidate (RC) for more people to try.

DNSB · 10-16-2026, 03:50 PM

My latest test build for Windows can be downloaded from the link in the Downloading Sigil test builds for Windows thread.

KevinH · 10-16-2026, 05:10 PM

Quote:

Originally Posted by DNSB

My latest test build for Windows can be downloaded from the link in the Downloading Sigil test builds for Windows thread.

Thank you!

10-11-2026, 08:45 AM	#47
DiapDealer Grand Sorcerer Posts: 29,842 Karma: 212614993 Join Date: Jan 2010 Device: Nexus 7, Kindle Fire HD	I've seen several reports that jxl is engineered for high-efficiency encoding and decoding directly on the CPU across mobile and desktop devices without needing specialized hardware support. In fact: Disabling hardware acceleration in Chrome forces the browser to rely on software rendering through the CPU rather than offloading tasks to the GPU. If a GPU driver is buggy, outdated, or poorly optimized for a specific image rasterization path, falling back to CPU software rendering can eliminate lag or stutter. This has definitely been my experience with the huge jxl images (as well as avif) on multiple Windows machines. A tired Windows 10 laptop, a beefy Windows 11 gaming desktop, a Windows 11 qemu vm on a stout Linux host, and a newer high-end Windows 11 mini-pc. The speedup on jxls when disabling gpu hardware acceleration still doesn't make sense since Preview is converting them on the fly to jpg (95%). The only explanation is that large jpgs benefit from using software rendering in chrome on Windows as well. I believe I'm going to start disabling WebEngine's GPU acceleration by default on Windows from now on. Last edited by DiapDealer; 10-11-2026 at 08:53 AM.

10-16-2026, 10:12 AM	#54
KevinH Sigil Developer Posts: 10,140 Karma: 7640000 Join Date: Nov 2009 Device: many	Hi All, I think I am done farting around with the future Sigil 2.8.5 unless something is broken. Except for forthcoming updated translations, I have hopefully pushed the last change. The upcoming 2.8.5 release actually includes a huge number of changes, bug fixes, and new features including a complete overhaul of the css parser used inside Sigil which should help keep Sigil up to date when it comes to CSS selectors for at least a little bit. It also completely changes the internals of all our singleton classes to be safer. New image formats were added (avif, jxl), updated image editing, new custom special characters, etc, etc., etc. In hindsight this probably should have been named Sigil 2.9.5 or even Sigil 3.0.0 but ... we can save 3.0 for when we next update to the latest Qt, latest Python, latest lexbor, latest pcre2, etc. In all my testing, it has been really stable, but of course there still could be issues that I have just not triggered given how I use Sigil. So please build from master and start using it on a normal basis and let me know if you run into any difficulties. Updated, hopefully final, translations should be coming in just over a week or two (to give translators time to make any changes they want). Thank you. Once we get final translations, if needed we can create a public release candidate (RC) for more people to try. Last edited by KevinH; 10-16-2026 at 10:32 AM.

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10-11-2026, 09:52 AM	#48
KevinH Sigil Developer Posts: 10,140 Karma: 7640000 Join Date: Nov 2009 Device: many	I also thought about that. I think Calibre disables it as well fwiw.

10-11-2026, 12:26 PM	#49
DiapDealer Grand Sorcerer Posts: 29,842 Karma: 212614993 Join Date: Jan 2010 Device: Nexus 7, Kindle Fire HD	My Windows 11 Mini-PC holds its own with the monster-sized images fairly well (after disabling acceleration, excluding all of Sigil's binaries/folders from antivirus, and telling Windows to optimize performance for Sigil and QtWebEngineProcess), so I think I'm ready to put this test case to bed. If you want to use monster-sized avifs in your epubs on Windows, be prepared for some fairly sluggish Sigil performance regardless of your hardware.

10-11-2026, 01:11 PM	#50
KevinH Sigil Developer Posts: 10,140 Karma: 7640000 Join Date: Nov 2009 Device: many	Curious... How do you actually tell Windows to optimize performance for Sigil and QtWebEngineProcess? Is this akin to changing scheduling priority for specific processes on Linux?

10-11-2026, 01:54 PM	#52
KevinH Sigil Developer Posts: 10,140 Karma: 7640000 Join Date: Nov 2009 Device: many	FYI, disabling the GPU on my arm64 M2 Max using Sigil preferences and restarting Sigil, sped up loading avif slightly. So it is not just a Windows thing.

10-12-2026, 02:02 PM	#53
DiapDealer Grand Sorcerer Posts: 29,842 Karma: 212614993 Join Date: Jan 2010 Device: Nexus 7, Kindle Fire HD	Good to know. The bottom line here is that our plugins are working fine in image resources tabs. And as you already mentioned, we can't really help Preview (QtWebEngine) load anything any faster. Except recommending disabling acceleration, and rendering jxls as 95% jpgs, it's out of our hands.

10-16-2026, 03:50 PM	#55
DNSB Bibliophagist Posts: 55,164 Karma: 182532774 Join Date: Jul 2010 Location: Vancouver Device: Kobo Sage, Libra Colour, Lenovo M8 FHD, Paperwhite 4, Tolino epos	My latest test build for Windows can be downloaded from the link in the Downloading Sigil test builds for Windows thread.