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[lencioni]

In observing a lot of diffux runs, I noticed that the slowest examples are the ones with the largest viewports. I believe that we are spending a good chunk of time taking a screenshot of the whole page and then cropping it down to the element with ChunkyPNG. Although we've made some progress on cropping performance recently, I think there is more that we can do. Namely, I think our runs would be faster and consume less memory if we took a screenshot of just the element instead of the whole page and then cropping it down.

As far as I know, webdriver doesn't currently provide an API to take a screenshot of just a portion of a page. Figuring out how to do this might require adding a feature to webdriver or perhaps monkeypatching it somehow.

Since our runs are already pretty fast, I don't see this as a high priority at the moment, but I figured I'd document it here for when the time comes or if someone wants to pitch in.

[trotzig]

Maybe we should make a commit that updates the README with a section on performance, and then close this issue? We can mention

• using smaller viewports if large ones aren't needed
• avoid doing screenshotEntireScreen unless it's really needed
• avoid testing large components (break into smaller components instead)

[lencioni]

I think that documenting those things is a good idea. My intention with opening this issue was to record what I think we can do to make runs generally faster for everyone and I think it still applies, however I'm okay with closing this issue out.

[lencioni]

I think we can call this resolved with the release of Happo 4.