175411 - XUL scrollbar rendering is _extremely_ inefficient

Status: RESOLVED WORKSFORME

(Core :: XUL, defect)

Description

[Roland Mainz]

XUL scrollbar rendering is _extremely_ inefficient.
When you turn-off double-buffering you'll see that the XUL scrollbar redraws
itself _completely_ during move.

Steps to reproduce:
1. Set 
-- snip --
user_pref("viewmanager.do_doublebuffering", false);
-- snip --
do disable double-buffering (pref was introduced in bug 169483)
2. Go to http://www.mozilla.org/newlayout/xml/debugdemos/books/books.xml
3. Select "Toggle Style"-button to use the alternative style for books.xml
4. Use one of the scrollbars

Result:
The whole XUL scroller widget gets redrawn

Expected result:
While scrolling only the previous and new location of the thumb would be
redrawn.

Note that even the plain Xt/Athena scroller makes this better (e.g. it only
redraws old&new locations of the thumb) than the current XUL code.

Comment 1

[Rene Pronk]

I'm not actually seeing anything under Win2000 build 20030209 but it could still
redraw everything of course. It looks however as if the scrollbar does no
clipping. You can see that in e.g. the mailwindow when you make the threadpane
so small that the scrollbar doesn't fit anymore. You'll see the scrollbar
drawing through the splitter.

Comment 2

[Wayne Mery (:wsmwk)]

WFM 
- Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9pre) Gecko/2008051102 SeaMonkey/2.0a1pre
- Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008051206 Firefox/3.0