Links to an anchor within same page not working

[samuknet]

The issue occurs when there is a link to another anchor tag in the same document, identified by the ID attribute. The problem also occurs identically when the name attribute is used. Clicking the link in Servo does nothing, when it should instantly scroll to the anchor.

For example:

<a href="#end">Jump to end</a>
<div>
Lipsum....
Lots of text making a scroll...
...
...
<a id="end">End of text</a>
</div>

With the above example (with dummy text long enough to cause the page to have a scroll), clicking the "Jump to end" link in Servo does nothing.

Online test case here.

On this issue, @jdm says:

I suspect that the big FIXME in ScriptThread::scroll_fragment_point is hitting us here, since the result of the bounding box calculation is (0, 0, 0, 0).

[jdm]

I took a brief look at #8275 and felt intimidated. I tried using HTMLElement::OffsetTop and HTMLElement::OffsetLeft intead of the content bounding box, since they were implemented recently and theoretically understand stuff about layers etc., but I ran into #12595. @mrobinson what would be involved in fixing #8275 properly?

[mrobinson]

I have a feeling this may not be related to #8275 at all. I ran the test with:

./mach run https://samuknet.github.io/test_cases/anchorInPageID/ -Z dump-layer-tree

The output is:

┌ Layer tree
│  ├─ Root Layer (pipeline=(0,0)) (0-FragmentBody-0) (512,370 at 0,0) (masks children) (3D context)
│  │  └─ Layer (140470021898496-FragmentBody-0) (512,3811 at 0,0) (3D context)

This suggests that servo has not layered the page beyond the root layer. I cannot remember exactly now, but I think that #8275 applies specifically in situations with overflow:scroll.

[nox]

This still doesn't work.

[CYBAI]

I can reproduce this issue that I cannot navigate to any random picture when I clicked on the random button which is an anchor in xkcd

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