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How to render in WebKit

Chromium#Eric Seidel#WebKit#rendering#painting#Tech Talk
76K views|14 years ago
💫 Short Summary

The video discusses the WebKit engine, its rendering process, including parsing, DOM tree creation, and render tree attachment. It covers RenderObject Trees, RenderStyles, and RenderLayers in web development. The relationship between the Rendering Tree and DOM Tree is explained, along with painting phases, HTML editing, and Hit Testing. It also touches on generating C++ from IDL files, bug filing, Undo/Redo events, and building DOM trees on demand. The importance of layout completion before queries, object ownership with Ref and pasref pointers, and reading WebKit.org documentation for developers is emphasized.

✨ Highlights
📊 Transcript
Overview of WebKit engine and its components.
WebKit has almost 2 million lines of code, mainly in C++, and is used to draw web pages.
WebCore is responsible for rendering, while JavaScriptCore or V8 handles JavaScript.
Loading data into WebKit is complex with multiple layers within WebCore.
Different stages like policy and provisional phases determine actions like allowing pop-ups or downloads.
The loading and parsing process in WebCore involves creating a new process in Chromium and using interfaces like DocLoader and CachedResource.
XML and HTML parsers tokenize and parse data streams from the network to create a DOM Tree.
The DOM Tree is attached to produce a render tree, which holds style information and links to plug-ins.
The RenderObject Tree is created for rendered content and is essential for painting.
RenderObjects handle layout, painting, size calculations, and style information, with display properties like 'display none' impacting the creation of render trees.
Overview of RenderObject Tree and RenderStyle in web development.
RenderStyles store computed style values such as color and shadow.
RenderObjects can share styles for memory efficiency but caution is needed when modifying styles outside the CSS system.
RenderStyleObjects are shared but not immutable.
RenderLayers are discussed for transparency and scrolling, appearing as textures on devices.
Relationship between Rendering Tree and DOM Tree in web development.
Rendering Trees hold Shadow Trees and hidden elements.
Layout process compared to Gecko's reflow method involves saving repaint rectangles, updating changes from the DOM, laying out children, and repainting based on parent metrics.
Layout is triggered on demand by changes requiring a repaint.
Steps of parsing, building the Rendering Tree, and lazily performing layout.
Overview of painting and rendering in web browsers, focusing on the Rendering Tree and incrementality.
Discussion on phases of painting, GraphicsContext abstraction, and RenderTheme for various platforms.
Explanation of HTML Editing in WebCore, covering text entry and rich text editing.
Touching on Hit Testing, selection handling, execCommands, and Undo/Redo operations.
Brief overview of JavaScript DOM Bindings and code generation from IDL files for exposing DOM Tree to different languages.
Generating C++ from IDL files for JavaScript, JNI bindings, and WebCore providing DOM elements.
The talk discusses the process of filing bugs at bugs.WebKit.org and fixing them.
Resources for writing test cases and contacting WebKit developers are highlighted.
Explanation of 'in files' used for Perl Scripts, atomic string caches, and element support.
Implementation of Undo/Redo events at the OS level and building DOM trees on demand with dependency levels between different trees.
Key Highlights:
The importance of understanding the concepts of paint and layout in WebCore is emphasized.
Incomplete layouts are not supported, requiring the entire document to be laid out before queries are answered.
The use of Ref pointers and pasref pointers for object ownership is explained for maintaining object lifecycle.
Developers are encouraged to read a document on WebKit.org regarding pointer usage in WebKit code.