CSS Selector Profiler, Source Mapping and Software Rendering

Published on in Google Chrome, Last Week, tech, WebKit. Version: Chrome 18

Happy New Year! Since I didn’t publish an update last week, this one will cover all 680 WebKit and 986 Chromium commits made in the past two weeks. Highlights include a ton of Web Inspector changes, Jarred’s work on XMLHttpRequest and access to new JavaScript features through about:flags.

Besides support for true hardware acceleration, which pretty much is a requirement for features such as WebGL and CSS 3D Transforms, attention is also being given to software renderers. Several crashes for Apple’s OpenGL-software renderer have been fixed, and support for SwiftShader has been added for Windows installations, which will automatically be downloaded if support for GPU-based WebGL is blacklisted. While performance definitely won’t be en par with GPU-based WebGL, it’s a good solution for those on older systems.

The Web Inspector team landed some great new features, most notable of which is the CSS Selector Profiler. Available through the Profiles Panel in the Inspector, it will show the number of matches for a certain element and its contribution to the total style matching run-time. Two other new features, both displayed in the image below, are the ability to dock the Web Inspector to the right-side of the browser window (through the Settings window) and an experimental tabbed interface for the Script Panel.

New, experimental Web Inspector features will be hidden behind a command line flag and a setting. Tree views in side-bars cannot be collapsed anymore using the keyboard and subsequent @rule-statements in CSS will be highlighted. The ability to remove all breakpoints has been added, as has a cool Go To Function dialog. Finally, Web Inspector gained support for Source Mapping through the X-SourceMap HTTP header. When enabled (also through the Settings window), an Install Source Map context-menu item will be added to scripts in the Script Panel.

On Chromium’s side for Web Inspector, both the chrome.devtools and the chrome.debugger Extension APIs graduated from being experimental, so hopefully we’ll be seeing a lot of extensions starting with Chrome 18!

WebKit’s HTML5 parser has received a number of updates, which include support for the Noah’s Ark condition, 93 named entities which expand to more than a single character and some minor fixes related to NULL characters in HTML content. Video subtitles through the <track> element can now be rendered on a video, and subtitles will be enabled for WebKit-mac builds, meaning Safari. Finally, the dropzone attribute got aligned with the specification.

The XMLHttpRequest implementation has also been updated, which now compares the mime-types in a case insensitive way, gained support for the loadend event and allows more liberal modification of the withCredentials and responseType attributes. More excitingly, new response types (such as json) won’t support synchronous requests in a non-worker scope anymore. Two more init*Event methods have been removed, and retrieving the computed style of the border-style, border-color and margin properties has been implemented.

Default styling of the strong and b elements has been updated to be bold rather than bolder. CSS Filters may now be used on inline elements, the blur filter will now invalidate the entire element and animating brightness, contrast and drop-shadow filters won’t be reversed anymore, and two more issues with full CSS 2.1 support have been fixed.

Other changes which occurred during these weeks:

And that’s all again. Two bugs to keep an eye out for this week are updated patches for CSS calc()’s parsing and the beforeprint and afterprint events.

10 Responses to “CSS Selector Profiler, Source Mapping and Software Rendering”

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January 3, 2012 at 5:24 pm

I like the CSS Profiler 😀 Can’t wait for cool Dev Tools Extensions

One question: When will be the next Dev Channel update out? The latest update is from the 15th of december 2011

That CSS Profiler looks like it will be pretty damn useful. A good way of keeping track of page elements.

But I am rather happy about the better inclusion of CSS Filters. That’s made my day.

Wow nice update guys! I use the Web Inspector all day long and am loving the progressive updates. Thanks for a great debugger!

Jacob Rask

January 4, 2012 at 8:36 pm

Can I read more about which ES.Next features are implemented somewhere?