rendering

Using the Paint Timing API

It's a great time to be a web performance aficionado, and the arrival of the Paint Timing API in Chrome 60 is proof positive of that fact. The Paint Timing API is yet another addition to the burgeoning Performance API, but instead of capturing page and resource timings, this new and experimental API allows you to capture metrics on when a page begins painting.

If you haven't experimented with any of the various performance APIs, it may help if you brush up a bit on them, as the syntax of this API has much in common with those APIs (particularly the Resource Timing API). That said, you can read on and get something out of this article even if you don't. Before we dive in, however, let's talk about painting and the specific timings this API collects.

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Understanding the Critical Rendering Path

Ire Aderinokun:

There are 6 stages to the CRP -

  1. Constructing the DOM Tree
  2. Constructing the CSSOM Tree
  3. Running JavaScript
  4. Creating the Render Tree
  5. Generating the Layout
  6. Painting

I imagine if you're really getting into performance work, you'll want a firm understanding of this. There are lots of ways to block/delay parts of this process. The job of a perf nerd is to understand when and why that's happening, evaluate if it's necessary or not, and tweak things to get to that painting step as soon as possible.

I'm curious if this is generic enough that 100% of all rendering engines work 100% the same way, or if there are significant differences.

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