Str: 1. Open this URL: data:text/html,<div>block</div><ul><li>li</li></ul> 2. Retrieve the accessible for the document. 3. Retrieve the line offsets at offset 0. Expected: (0, 1) Actual: (0, 2) 4. Retrieve the line offsets at offset 1. Result (correct): (1, 2) Impact: This causes ATs to report that the list is part of the line with the block when it isn't.
here's an example how a test may be constructed: https://dxr.mozilla.org/mozilla-central/source/accessible/tests/mochitest/text/test_lineboundary.html#33,34-36 as long as we have a test case, the next step is to figure out where's out expectations are broken, I suppose that a start point for the debugging could be at HyperTextAccessible::FindOffset.