Steps to reproduce: 1. Load the testcase. 2. Try to scroll right to see what tag caused the parse error. Result: Notice that two-finger scrolling doesn't work, and that the horizontal scrollbar is kinda-present but disabled. This regressed between 2007-01-29 and 2007-01-31, so I'm guessing it's a regression from bug 18333.

This sounds like a layout bug.

Did bug 380612 fix this symptom? If so, should there be a bug on the underlying scrollbar layout problem (which seems like a valid bug even if this symptom went away)?

(In reply to comment #2) With the 2007-05-31-18/OS X Minefield build * The scrollbar sort of works: there is a scrollbar widget but: click on the thumb and it jumps 1/3 of the screen (left to right). Dragging is not possible. Going back from right to left can only be done by using the arrows. * Using scrollwheel or trackpad works fine though.

Looks like basically bug 78070.

(In reply to comment #3) At least on current trunk builds /linux there is no way I can get the horizontal scrollbar to move, not even whey selecting all the text of a row using keyboard navigation.

I suppose I'll be following this bug. I decided to start bisecting, and discovered following: Trunk: 2007-01-27-04 works 2007-02-01-04 broken differently - a scrollbar is presented, but it is full width, as if the content is just slightly larger than the screen (which is not the case). 2007-03-01-04 and up, broken with a scrollbar that is the correct width, but unuseable. I was using: http://m8y.org/tmp/invalid.xhtml as a test. Given the dates, bz's bug reference seems too early, but perhaps it is some ongoing thing.

"My bug reference" is to the bug that causes the problem. That bug is only an issue if the root element is replaced after frame construction has started. That never used to happen with XML until incremental XML parsing. See comment 0. Various later changes in behavior are probably due to changes in scrollframe, but don't affect the basic problem.

The patch for bug 78070 fixes this bug, but I'm not quite sure how to write a test for this....

And in particular, reftest doesn't do scrollbars on the test, from what I can tell. And even if it did, I'm not sure how to test for brokenness of them.

Put the XML document with the error inside an iframe?

Hmm... That does show them (including in current builds), but still not sure how to test that they work. I'll poke at it.

OK, I've finally managed to write a mochitest for this. I'll include it in the patch for bug 78070.

Fixed by checkin for bug 78070.

This test seems to have failed on windows recently: http://tinderbox.mozilla.org/showlog.cgi?log=Firefox/1242141320.1242147345.30727.gz

That random failure is filed as bug 492575.