238423 - Rendering / scrolling resized images chews up CPU far too much.

Status: RESOLVED DUPLICATE of bug 163975

(Firefox :: General, defect)

Description

[Dan Kamins]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6) Gecko/20040210 Firefox/0.8
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6) Gecko/20040210 Firefox/0.8

When scrolling content with images that are resized (either via
style="width:???" or img width="???"), CPU usage spikes and scrolling/UI is very
jerky.  Just rendering pages with resized images has a lag spike too.  

Mozilla bug #215090 is related, but was filed too specifically regarding
keyboard events.

See the test cases at:
http://www.axonchisel.net/etc/test/200403-firefox-img-scroll-bug-test.html


Reproducible: Always
Steps to Reproduce:
1. Go to the test case at:
http://www.axonchisel.net/etc/test/200403-firefox-img-scroll-bug-test.html
2. Scroll the test cases (#2 and #3) and witness CPU usage spike.

Actual Results:  
CPU usage spikes 100%, scrolling is jerky, whole browser feels sluggish.

Expected Results:  
Render resized images gracefully.  Even images at exactly half size are getting
hit by this.  There appears to be a bug in the resize code that is doing extra
redundant calculations, perhaps re-calculating the image on each mouse movement
event.

Comment 1

[Jesse Ruderman]

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