It looks like we handle very large blur radii properly, but it'd be nice to have an automated test for them (e.g. "filter: blur(100000px)").

Firefox seems to freeze for me for such values.

(In reply to Tim Nguyen [:ntim] from comment #1) > Firefox seems to freeze for me for such values. Yeah, it hangs a bit for me too with large values. Right now, we cap the blur radius to 500px. My 2011 MacBook Pro starts hanging noticeably at radii of 300px+, using software rendering. I haven't tested how the Windows D2D backend performs. Or mobile, for that matter. Perhaps we should lower the cap, at least for software rendering? Markus, do you have any thoughts about this?

I think lowering the cap for software filters is a good idea. We could have FilterNodeSoftware apply its own cap, by capping mStdDeviation in FilterNodeGaussianBlurSoftware::SetAttribute and FilterNodeDirectionalBlurSoftware::SetAttribute.

This patch caps blur radii to 100px when rendering in software. I added some tests to verify that directional and non-directional blurs are capped. However, I wasn't quite sure how to make the tests force software rendering of filters. I ended up with "skip-if(d2d) pref(layers.acceleration.disabled,true)", so the tests at least run on Mac and Linux, and the assumption is that layers will have to be accelerated for filter rendering to be accelerated (when that's implemented). Here are some perf results I used to choose a cap of 100px. I blurred a 1000x1000 solid colored div: Macbook Pro Mid 2010, Firefox Nightly 34.0a1 (2014-09-02) Blur radius / Time 10px => 64ms 50px => 98ms 100px => 155ms 200px => 320ms 300px => 514ms 400px => 4066ms (OS X shows beachball) 500px => 5680ms (OS X shows beachball) Nexus 7, Firefox 32: 10px => 2118ms 50px => 6004ms 100px => 13646ms Arguably, we could still go lower because it still takes 13 seconds to render a 100px blur on mobile, but I'm worried that's capping it fairly low.

Comment on attachment 8483056 [details] [diff] [review] Patch Sounds good to me.

Comment on attachment 8483056 [details] [diff] [review] Patch https://hg.mozilla.org/integration/mozilla-inbound/rev/3ec65eb63c17 https://tbpl.mozilla.org/?tree=Try&rev=329096e4b380