Wednesday, October 29th, 2008

Chrom(e|ium) Details: I/O, Responsiveness, UI, and Graphics

Category: Chrome, Google

The Google folks have been doing a really good at consistently blogged about the decisions that were made as they created Chrome:

Graphics in Google Chrome

Google Chrome uses a library called Skia, which is also the graphics engine behind Google’s Android mobile OS. The two projects share code that implements WebKit’s porting API in terms of Skia. Google Chrome also uses Skia to render parts of the user interface such as the toolbar and tab strip. I’m going to talk about some of the history that led us to choose Skia, as well as how our graphics layer works.

I/O in Google Chrome

We moved the I/O onto a number of background threads which allow the user-interface to proceed asynchronously. We did this for large data sources like cookies, bookmarks, and the cache, and also for a myriad of smaller things. Writing a downloaded file to disk, or getting the icons for files in the download manager? The disk operations are being called from a special background thread. Indexing the contents of pages in history or saving a login password? All from background threads. Even the “Save As” dialog box is run from another thread because it can momentarily hang the application while it populates.

Content, not ‘Chrome’

To achieve the streamlined feel we were after, we knew we would have to cut some things, and while we had our own intuitions about what was and wasn’t useful in current browsers, we had no idea how those ideas matched to reality. So in typical Google fashion, we turned to data; we ran long studies of the browsing habits of thousands of volunteers, compiled giant charts of what features people did and didn’t use, argued over and incorporated that data into our designs and prototypes, ran experiments, watched how our test users reacted, listened to their feedback, and then repeated the cycle over and over and over again.

Even the the more subtle parts of our first-level UI were subjected to similarly intense scrutiny – “what shade of blue best suits XP users”, “should the tabs start 18 or 19 pixels below the top of the window?”, “what’s the correct offset between our buttons?”. The answers to these questions were debated and tested for our entire development cycle, and we saw that opinions consistently differed greatly depending on whether we had been Windows 3.1, OS7 or even NeXT users and developers.

The Google Chrome Sandbox

Google Chrome’s multi process architecture allows for a lot of flexibility in the way we do security. The entire HTML rendering and JavaScript execution is isolated to its own class of processes; the renderers. These are the ones that live in the sandbox. We expect to work in the near future with the plug-in vendors to securely sandbox them as well.

I have to admit that I personally wish Cairo was chosen, as having the Google engineers behind that project would have been amazing, and benefit would be had for all of the applications that use it.

Posted by Dion Almaer at 8:14 am
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3.7 rating from 17 votes

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We use chrome and really like it.

Comment by RawChocolate — July 30, 2009

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