Created attachment 173087 [details] demo html file SUMMARY The CSS :is pseudo-class appears to be ignored by Falkon. STEPS TO REPRODUCE 1. Go to https://developer.mozilla.org/en-US/docs/Web/CSS/:is and look at the CSS Demo. Or load the attached file. OBSERVED RESULT The list renders as entirely blue in Falkon. EXPECTED RESULT The list renders in blue, green and orange, like it does in Firefox. SOFTWARE/OS VERSIONS Ubuntu 22.04 Falkon application version 3.2.0, Ubuntu package version 3.2.0+dfsg1-1 QtWebEngine version 5.15.3
Created attachment 173088 [details] firefox and falkon rendering
According to the "Browser Compatibility" table from the provided link[1], this feature was added to Chromium (Chrome) 88. The QtWebEngine version provided in this bug report (5.15.3), it uses Chromium 87 as a backend. So it is not implemented there, because it is too old. Works perfectly fine on newer Falkon with Qt6 backend. PS: You can check the Chromium version used for given QtWebEngine version at Qt wiki[2]. [1] https://developer.mozilla.org/en-US/docs/Web/CSS/:is [2] https://wiki.qt.io/QtWebEngine/ChromiumVersions