342654 - Scrolling big down scaled jpgs causes 100% CPU load and choppy redraw

Status: RESOLVED DUPLICATE of bug 163975

(Firefox :: General, defect)

Description

[Werner]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4

When i scroll jpgs on homepages which are scaled down via "scaleImg()" for example the CPU load rises to 100% no matter how fast i scroll. The redraw of the picture entering the screen is very choppy. 

It also happens when i move a window in front of the scaled jpg.

The choppy scrolling does not happen when the the windows graphics hardware acceleration is turned down one notch. (under view properties -> problems). The CPU load is lower then, more like 60%.

It is propably important that the problem came first to my attention after i changed to an ATI graphics card from a Nvidia GF 4. Older ATI drivers show the same problem.

All the other tickets with scrolling CPU load dont show any high CPU effect on my system so i expect this to be a new bug.

Reproducible: Always

Steps to Reproduce:
1. Open a homepage with a scaled big jpg like http://img222.imageshack.us/my.php?image=testbild17yl.jpg
2. Scroll up and down or move a window in front of the jpg

Actual Results:  
Scrolling and redraw is very choppy.

Expected Results:  
Smoth scrolling and a CPU load of like 50% or much less.

Computer config:
XP prof SP2
A64 3500+
1 GB RAM
Sapphire X800GT AGP graphics with catalyst 6.5

Comment 1

[Eli Friedman]

Interesting report.  I'd suggest adding a comment to the existing bug.

*** This bug has been marked as a duplicate of 163975 ***

Comment 2

[Werner]

I have looked closely at 163975 before i posted my report and partly disagree on mine being a duplicate of it. 
I have tried both, the PNG example and the weathermap one and both show a CPU load of 1-2% when scrolling or hovering.
Especially the mouse over never gave me any problems.

179662 and 238423 which have been merged into 163975 both seem to match my report BUT for my computer the resized pictures are so small that only like 50% CPU load is caused.

Im new to bugzilla ticket system so however if you think this is to closely related to 163975 ill add my findings there.