hawaiiloha.blogg.se - Firefox developer edition tutorial

The rule that has the highest specificity wins. Then it sorts the declarations based on different columns. The CSS engine basically creates a spreadsheet. How does the CSS engine know which value to pick? Plus, the browser itself adds some default CSS (called user agent style sheets). Because multiple rules can match, there may be multiple declarations for the same property.

fill in any missing values with values from the parent or a default value-aka the cascadeįor this step, we’ll add any rule that matches the DOM node to a list.

figure out which rules apply to the node - aka selector matching.

To do this, the CSS engine needs to do two things: And for each form field, they need to have an answer. They need to fill out one of these forms for each DOM node. I think of it kind of like somebody going through and filling out a form. As part of this, it gives the DOM node a value for each and every CSS property, even if the stylesheets don’t declare a value for that property. It goes through each DOM node, one by one, and figures out the styles for that DOM node. This means when it starts calculating the styles, the CSS engine has two things: This image will then be rendered on the screen. This is basically like taking a picture of the layers stacked together.

Take those different painted layers, apply any compositor-only properties like transforms, and turn them into one image.

That makes it possible to just change one layer without having to repaint things on other layers. I think of this like old-time hand drawn animation, with onionskin layers of paper. The boxes don’t just represent DOM nodes… you will also have boxes for things inside the DOM nodes, like lines of text. Boxes are created for each thing that will show up on the screen.

Figure out dimensions for each node and where it goes on the screen.

Then it figures out values for each CSS property for that DOM node. For each DOM node, the CSS engine figures out which CSS rules apply.

Figure out what the elements should look like.

It doesn’t know what those elements should look like, though.

It knows about parent/child relationships between elements.

At this point, the DOM knows about the structure of the page. Parse the files into objects the browser can understand, including the DOM.To get from files to pixels, all of these rendering engines basically do the same things: The rendering engine takes the website’s HTML and CSS files and turns them into pixels on the screen.Įach browser has a rendering engine.

The CSS engine is part of the browser’s rendering engine.

Then we can look at how Quantum CSS makes it all faster. So even if it weren’t running in parallel, it would still be one fast CSS engine.īut what does the CSS engine do? First let’s look at the CSS engine and how it fits into the rest of the browser. On top of that, it combines existing state-of-the-art optimizations from other browsers. This means it can run up to 2 or 4 or even 18 times faster. It takes advantage of modern hardware, parallelizing the work across all of the cores in your machine. This new engine brings together state-of-the-art innovations from four different browsers to create a new super CSS engine. You can make sure that it’s turned on for you by going to about:config and setting to true. We’re making the changes in place, component by component, so that you can see the effects in Firefox as soon as each component is ready.Īnd the first major component from Servo-a new CSS engine called Quantum CSS (previously known as Stylo)-is now available for testing in our Nightly version. The project has been compared to replacing a jet engine while the jet is still in flight. We’re swapping in parts from our experimental browser, Servo, and making massive improvements to other parts of the engine. You may have heard of Project Quantum… it’s a major rewrite of Firefox’s internals to make Firefox fast.