The Layout Engine or Web Browser Engine

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Introduction A Layout Engine is known by many names like a Rendering Engine or a Web Browser Engine. It is a software component that reads the marked up content along with its formatting information. Based on this, it displays the content (formatted) on the screen. The marked up content includes the HTML files, XML files, image files among others and the formatting information is given by the CSS files. So, it is safe to say that the web engine paints the content area that is to be displayed on a monitor or printed by a printer. There are different ways in which a layout engine may operate. Sometimes, engines wait to receive all the data before it renders the page. It may also begin rendering the page before it receives all the data. This can lead to the pages changing as further data is received. For eg. Sometimes, the web page gives a flash of unformatted content before the entire page is loaded. This is caused because rendering had been already started before the formatting information (CSS files) was received by the browser. Basic Working: The engine takes the URL and a set of window content area rectangle. URL provides the document to fill in the content. The document includes everything that a web page has like links, forms, plug-ins etc. So, as we see the layout engine does bulk of the work. Rest of the features like menu bars etc. are provided by the host application itself. Commonly, a web engine is embedded in the web browsers. Other applications that require displaying of web content also have web engine in them like on-line help systems or e-mail clients. Layout Engines of some popular Web Browsers: • Google Chrome – Blink • Mozilla Firefox – Gecko • Internet Explorer – Trident • Safari – WebK... ... middle of paper ... ... For the above code, the parse tree will look something like this- But the job of the rendering engine is not limited till here. The styling of the pages is also handled by the same rendering engine. The following figure gives a good idea of how the CSS (style sheets) are handled by the engine. Conclusion Introduction of a new rendering engine like Blink in place of the efficient WebKit was bound to bring a lot of changes in the way web is perceived and worked with in the world. It has significant implications. Still, it is believed that presence of multiple layout (rendering) engines will only be beneficial to the web and will encourage us to further innovate in this field. Over the long run, this will definitely lead to a more stable web with fewer bugs and more reliability.

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