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Browser internals

Browser internals. Ivan & Bastiaan. Major browsers. Firefox Chrome Safari IE Opera. Firefox- open source Chrome is based on Chromium which is open source Safari - partly open source. Statistics. Main functionality. Presentation of data(HTML documents, images etc.)

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Browser internals

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  1. Browser internals Ivan & Bastiaan

  2. Major browsers • Firefox • Chrome • Safari • IE • Opera Firefox- open source Chrome is based on Chromium which is open source Safari - partly open source

  3. Statistics

  4. Main functionality • Presentation of data(HTML documents, images etc.) • Resource location specified by URI(Uniform Resource Identifier) • W3C • Compatibility issues

  5. User Interface • Address bar • Back/forward buttons • Home button • Menu • Every part of the browser except the main window where you see the requested page.

  6. Engines Browser Engine • Handles actions between UI and Rendering Engine Rendering Engine • Parsing HTML,CSS • Displaying parsed content • Displaying requested content(PDF, Images etc.)

  7. Other main components • Networking • Using for network calls (HTTP request) • UI backend • Painting the render tree • JS interpreter • Parses and executes JS code

  8. Data storage • Persistence • Saving data on hard disk(cookies) Html 5 defines ‘web database’

  9. Structure Chrome holds multiple instances of the rendering engine - one for each tab

  10. Rendering Engine Gecko - Firefox WebKit – Chrome,Safari WebKit started as engine for Linux platform and was modified by Apple to support Mac and Windows

  11. The main flow • Content in 8K chunks Syntax analyze of HTML  Turn the tags into DOM nodes(“content tree”) Parsing the style data(external CSS and style tags)  Render tree Giving each node coordinates  Painting the render tree Rendering engine will try to display content as soon as possible

  12. WebKit main flow

  13. Gecko main flow

  14. Differences • Gecko • Frame tree • Reflow • Frame constructor • Content sink to form DOM elements • WebKit • Render tree • Layout • Attachment

  15. Parsing • Result of parsing is nodes tree • Example-parsing expression 2+3-1 returns this tree Parsing a document means translating it to some structure.

  16. Parsing rules • Based on syntax rules that document obeys(language or format) • Context free grammar • Syntax analysis and lexical analysis

  17. Analysis Lexical breaking input into tokens(lexer) Syntax  applying syntax rules(parser)

  18. Analysis • Parser asks for a new token • Trying to match • Token added

  19. Compilation example • Source code will be parsed first • Translation into machine code

  20. Rendering • Single threaded • Main thread is an event loop(infinite) • Except network operations • Number of parallel connections is limited(2-6 connections) Event loop waits for events (like layout and paint events) and processes them

  21. Questions

  22. With thanks to TaliGarsiel & Paul Irish autors of this article: http://www.html5rocks.com/en/tutorials/internals/howbrowserswork/

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