What is the rendering principle of the browser?

The rendering principle of the browser refers to the process of how the browser displays the web page content on the user interface when the user uses the browser to access the web page. The rendering principle of the browser involves multiple steps, including parsing HTML, building DOM tree, calculating CSS styles, generating rendering tree, layout and drawing, etc. Detailed introduction: 1. Parse HTML. When the user enters a URL in the browser or clicks a link, the browser will send a request to the server to obtain the HTML file of the web page. The browser begins to parse the HTML file, build a DOM tree, and so on.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

The rendering principle of the browser refers to the process of how the browser displays the web page content on the user interface when the user uses the browser to access the web page. The rendering principle of the browser involves multiple steps, including parsing HTML, building DOM tree, calculating CSS styles, generating rendering tree, layout and drawing, etc. This article will introduce the rendering principle of the browser in detail.

First, when a user enters a URL in the browser or clicks on a link, the browser will send a request to the server to obtain the HTML file of the web page. Then, the browser starts parsing the HTML file and building a DOM tree. The DOM tree is a tree structure composed of HTML tags and their hierarchical relationships, which represents the structure and content of a web page.

In the process of parsing HTML, the browser will encounter the CSS style sheet, and the browser will calculate the style of each element based on the CSS style sheet. This process is called calculating CSS styles. The browser will match elements based on the selector and apply the corresponding style rules to calculate the final style of each element.

Next, the browser will generate a rendering tree based on the DOM tree and style information. The rendering tree is a tree structure composed of visible elements in the DOM tree and their style information, which represents the layout and appearance of the web page. Each node in the rendering tree is a visible element, including text, pictures, tables, etc.

In the process of generating the rendering tree, the browser will calculate the geometric attributes of each element, such as position, size, etc., based on the element's style information. This process is called layout. After the layout is completed, the browser will draw based on the structure and geometric properties of the rendering tree to display the web page content on the user interface.

During the drawing process, the browser converts each node in the rendering tree into pixels on the screen. The browser uses graphics libraries to draw pixels to the screen, forming the final user interface.

In addition to the above main steps, the browser's rendering process also involves some other optimization techniques to improve rendering performance and user experience. For example, browsers layer render trees, dividing complex render trees into multiple layers for better management and drawing. Browsers also use asynchronous rendering technology, which divides the rendering process into multiple stages and performs other tasks between each stage to improve response speed.

To sum up, the rendering principle of the browser is to display the web page content on the user interface by parsing the HTML file, constructing the DOM tree and calculating the CSS style, generating the rendering tree, performing layout and drawing and other steps. The browser's rendering process also involves some optimization techniques to improve rendering performance and user experience. Understanding the rendering principles of browsers is very important for front-end developers and web designers to help them optimize web page performance and improve user experience.

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