449781 - Dragging a zoomed tab applies zoom to chrome

Status: RESOLVED FIXED

(Core :: DOM: Navigation, defect)

Description

[Boris Zbarsky [:bzbarsky]]

STEPS TO REPRODUCE:

1) Load a page in a tab
2) Zoom in a few times
3) Drag the tab to a different window

ACTUAL RESULTS: Chrome in the different window gets the zoom applied

EXPECTED RESULTS: don't mess with me chrome, I tells you!

Many thanks to [e-mail] for spotting this.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Oh, this is fun.  Apparently it's been broken all along, actually, for cases when a subdocument went display:none then back to visible.  We just never ran into it much, because apparently we don't run into too much trouble if multiple content frames share the same device context?

That's what's going on here: the content document ends up with the chrome device context, because unlike DocumentViewerImpl::Init (which gets the device context passed in), DocumentViewerImpl::Show just grabs the device context off the parent widget... which is SO the wrong thing to do.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Attachment: Patch to fix

roc, any idea how to test this?  Basically we're screwing up the pixel scale on our parent frame's device context....

If DrawWindow uses the same device context as normal painting, it would be pretty easy to write a reftest for this using enablePrivilege, I guess.  Have a child which is hidden-visibility, set it to display:none, then display:whatever, then zoom the child and compare to our initial state, or something.  Would that work?

Comment 4

[Robert O'Callahan (:roc) (email my personal email if necessary)]

I think that would work.

Comment 5

[Håkan Waara]

Will bug 408496 be fixed, or is it maybe related?

Comment 6

[Boris Zbarsky [:bzbarsky]]

Maybe.  Hard to say from that bug.

Comment 7

[Boris Zbarsky [:bzbarsky]]

Pushed this, with a mochitest.  I added a little mochitest helper file for doing reftest-like stuff.

Comment 8

[Sylvain Pasche]

Changeset id (to see the mochitest):
http://hg.mozilla.org/index.cgi/mozilla-central/rev/1ecbdcb04b8e