MobileRead Forums - View Single Post - Suggestions for Sigil Improvements or New Features

KevinH · 02-13-2026, 08:09 PM

Okay, I can at least recreate this missing custom css bug on MacOS.

It seems we now actually do clear the entire cache. But QtWebEngine somehow treats a "reload" as different from a first load of an xhtml file and actually expects to find things in its local cache and if it can not it looks out on the net for the file and barfs on any "file:" urls in those injected stylesheets (and Mathjax).

Even though we tell Preview and QtWebEngine we are allowed to use local file: urls in the WebProfileMgr when they are not found in the cache on reload it generates an internal error that you can only see in the javascript console of the Inspector:

net::ERR_UNKNOWN_URL_SCHEME

as QtWebEngine has now disallowed the "file:" scheme we use for injected things like the custom css and the mathjax urls.

So this is a real bug in QtWebEngine but not one most people we ever hit so the likelihood of them fixing it will be very low.

The only "workaround" I can find for this limitation is to use our "sigil:" url scheme handler to elude their internal scheme handling bug.

I want to play around with this a whole bunch more before committing it.

A very strange bug to hit.

02-13-2026, 08:09 PM	#173
KevinH Sigil Developer Posts: 9,402 Karma: 6686152 Join Date: Nov 2009 Device: many	Okay, I can at least recreate this missing custom css bug on MacOS. It seems we now actually do clear the entire cache. But QtWebEngine somehow treats a "reload" as different from a first load of an xhtml file and actually expects to find things in its local cache and if it can not it looks out on the net for the file and barfs on any "file:" urls in those injected stylesheets (and Mathjax). Even though we tell Preview and QtWebEngine we are allowed to use local file: urls in the WebProfileMgr when they are not found in the cache on reload it generates an internal error that you can only see in the javascript console of the Inspector: net::ERR_UNKNOWN_URL_SCHEME as QtWebEngine has now disallowed the "file:" scheme we use for injected things like the custom css and the mathjax urls. So this is a real bug in QtWebEngine but not one most people we ever hit so the likelihood of them fixing it will be very low. The only "workaround" I can find for this limitation is to use our "sigil:" url scheme handler to elude their internal scheme handling bug. I want to play around with this a whole bunch more before committing it. A very strange bug to hit. Last edited by KevinH; 02-13-2026 at 08:12 PM.