519079 - text-shadow with huge blur makes Firefox very slow

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect)

Description

[Daniel]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)

A possible buffer-overflow when you enter much numbers into the css3 text-shadow option which causes the browser to jerk!

Reproducible: Always

Steps to Reproduce:
1. create an input field
2. setting the text-shadow with css like:  text-shadow:#000000 10px 10px 100000px;
3. last number has to be very big
Actual Results:  
firefox gets 99% systemusage and is jerking!

Expected Results:  
mh... doesn't show so big shadows!

Comment 1

[Michael Ventnor]

Buffer overflow would mean a crash, wouldn't it?

Cairo can deal with surfaces that are too large and we respect that. I think this surface probably isn't over the limit and Firefox is trying to do the shadow as normal, hence the jerking and 99%.

Comment 2

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

We should probably just cap the blur-radius at 200px or something. Anyone using a value larger than that is just trying to mess with us.

Comment 3

[Michael Ventnor]

Attachment: Patch

Comment 4

[Michael Ventnor]

I removed that RoundOut because it's not necessary, it happens in gfxBlur.

Comment 5

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

How about we limit it earlier so we get a decreases overflow area as well?

Comment 6

[Michael Ventnor]

Attachment: Patch 2

I heavily doubt this bug is a security issue, it seems to me the browser's just doing too much work.

Comment 7

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

Comment on attachment 403663 [details] [diff] [review]
Patch 2

style system -> dbaron

Probably want to cover text-overflow as well, though.

Comment 8

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

From a style system perspective, I'd rather the clamping happen outside (after) the style system, especially if there's only a single point there where it would need to be done, which I hope there is in this case.

Comment 9

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

Comment on attachment 403098 [details] [diff] [review]
Patch

Alright let's take this patch, and we can also take another patch to fix the overflow area.

Comment 10

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Comment on attachment 403663 [details] [diff] [review]
Patch 2

Minusing since I think we decided to take the other patch.

(Also, I can imagine people wanting blurs of similar size to the screen...)

Comment 11

[Daniel Veditz [:dveditz]]

No evidence of a security problem.

Comment 12

[Witold Czaplewski]

On http://50226.de/ I'm using text-shadow (the title links) in the pseudo-class :hover with following css: .entry h2 a {text-shadow:0 0 5px #FFF;}

As you can see the hover effect is extremly slow and the load (on a Core 2 Duo 6400, Windows 7 64, Firefox 3.6) goes up the 50%.

Other browsers like chromium doesn't show this issue.

Comment 13

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

Witold, can you file a new bug on that and CC me? I suspect the problem on your site is not text-shadow, but box-shadow plus the fact that hovering those headers repaints the entire page (not sure why that is).

Comment 14

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

Michael, do you want to check this in yourself, or do you want me to do it?

Comment 15

[Michael Ventnor]

http://hg.mozilla.org/mozilla-central/rev/b88494638342

Comment 16

[Eric Shepherd [:sheppy]]

Added a note to the text-shadow docs:

https://developer.mozilla.org/en/CSS/text-shadow