510799 - Visual glitch when switching to background tab if zoom changed after page loaded

Status: NEW

(Firefox :: General, defect)

Description

[Sylvain Pasche]

If a page is loaded in the background and the zoom level of that page's domain is changed afterward, when switching to the background tab the page is visible with the old zoom level for a few moment and then is redrawn with the new zoom level. This causes the whole page to jump.

Steps to reproduce:
1. Visit a site like http://en.wikipedia.org/wiki/Main_Page.
2. Load a couple of pages from the same site in the background by
middle-clicking e.g.
  http://en.wikipedia.org/wiki/Mozilla
  http://en.wikipedia.org/wiki/Mozilla_Firefox
  http://en.wikipedia.org/wiki/Page_zooming
3. Set text-zoom to larger or smaller than normal by pressing Ctrl + or Ctrl -.
4. Switch to the background tabs.
5. Optionally repeat steps 3, then 4.

Note: this is different from bug 510753 because the zoom level is changed *after* the background tabs have loaded.

This issue is not visible on Linux and OSX. See bug 510753 comment 5 and bug 510753 comment 9 for some explanations.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

I see this on OSX too.

Comment 2

[Jeff Muizelaar [:jrmuizel]]

Apparently the cause for this is setting the zoom on tab after drawing it. We should instead set the zoom before drawing it.

Comment 3

[Benjamin Smedberg]

Not blocking, but I'd take an appropriately-safe patch.