Bug 62923 – getComputedStyle doesn't work for pseudo elements on load

• Component: Layout and Rendering
• Status: RESOLVED CONFIGURATION CHANGED

[Sam Weinig]

Created attachment 97679 [details]
Test Case

window.getComputedStyle() doesn't seem to work for pseudo elements until unload.  It seems like the style is not available until it has been painted. Test case attached.

[Sam Weinig]

This is probably what the comment in Element::computedStyle is referring to when it states:

   // FIXME: Find and use the renderer from the pseudo element instead of the actual element so that the 'length'
   // properties, which are only known by the renderer because it did the layout, will be correct and so that the
   // values returned for the ":selection" pseudo-element will be correct.

[Sam Weinig]

Created attachment 97680 [details]
[WIP] Patch

This patch fixes the issue, but I am not sure it is the best the way to do it.  I am also not certain what should be done about the case of the element not in the tree/with no renderer.

[Ahmad Saleem]

With attached test case, I am getting this across all browsers (Safari Technology Preview 160, Chrome Canary 111 and Firefox Nightly 110):

In Script: rgb(0, 0, 0)
On Load: rgb(0, 0, 0)
On 100ms Timeout: rgb(0, 0, 0)
Button Clicked: rgb(0, 0, 0)

Is this still an issue? Thanks!

[Anne van Kesteren]

Seems like this was resolved indeed. The FIXME is also no longer present.