546033 - Scrolling while the viewport has a focus rectangle causes smearing

Status: RESOLVED FIXED

(Core :: Web Painting, defect, P2)

Description

[Ori Avtalion (salty-horse)]

Steps to reproduce:

1) Alt-tab until the entire viewport is in "focus" and has a rectangle around
it.
2) Scroll up/down.

Results:
The focus rect's dotted line will smear.

I found this happening beginning with the 2010-01-12 nightly builds.
Previously, the focus rect would immediately disappear after scrolling, so no
smearing is possible.

I assume bug 526394 is to blame.

Comment 1

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

Attachment: fix

Oops. When nsCanvasFrame::Init is called, the root nsHTMLScrollFrame has not yet been attached to the frame tree. Instead, let's just add the scroll position listener when the nsCanvasFrame actually gets focus ... and to avoid adding it multiple times, remove it when we lose focus.

Comment 2

[Neil Deakin]

Do you need to also remove the listener in RemoveScrollPositionListener?

Comment 3

[[e-mail]]

Comment on attachment 428639 [details] [diff] [review]
fix

You also need to deal with the case of a scroll changing mDoPaintFocus.

Comment 4

[Neil Deakin]

Bah, that's what I meant to say, but failed. I wanted to say remove the listener in ScrollPositionWillChange.

Comment 5

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

Attachment: fix v2

Good catch!

RemoveScrollPositionListener during the callback is bad. This approach is simpler. Just AddScrollPositionListener once when we first get focus.

Comment 6

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

http://hg.mozilla.org/mozilla-central/rev/34b13470f8ef