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https://github.com/netsurf-browser/netsurf
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109 lines
4.3 KiB
Plaintext
109 lines
4.3 KiB
Plaintext
Documentation for Developers
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This document contains an overview of the code for NetSurf, and any other
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information useful to developers.
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________________________________________________________________________________
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Source Code Overview
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The source is split at top level as follows:
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content -- fetching, caching, and converting content
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css -- CSS parser and interfaces
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desktop -- non-platform specific front-end
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render -- HTML processing and layout
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riscos -- RISC OS specific code
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utils -- misc. useful functions
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________________________________________________________________________________
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content -- fetching, caching, and converting content
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Each URL is stored in a struct content. This structure contains a union with
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fields for each type of data (HTML, CSS, images).
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The content_* functions provide a general interface for handling these
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structures. A content of a specified type is created using content_create(),
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data is fed to it using content_process_data(), terminated by a call to
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content_convert(), which converts the content into a structure which can be
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displayed easily.
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The cache stores this converted content. When content is retrieved from the
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cache, content_revive() should result in content which can be displayed (eg. by
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loading any images and styles required and updating pointers to them).
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Code should not usually use the fetch_* and cache_* functions directly, except
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for cache_free(). Instead use fetchcache(), which checks the cache for a url and
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fetches, converts, and caches it if not present.
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________________________________________________________________________________
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css -- CSS parser and interfaces
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CSS is tokenised by a flex-generated scanner (scanner.l), and then parsed into a
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memory representation by a lemon-generated parser (parser.y, ruleset.c).
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Styles are retrieved using css_get_style(). They can be cascaded by
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css_cascade().
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http://lex.sourceforge.net/
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http://www.hwaci.com/sw/lemon/
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________________________________________________________________________________
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render -- HTML processing and layout
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This is the process to render an HTML document:
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First the HTML is parsed to a tree of xmlNodes using the HTML parser in libxml.
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This happens simultaneously with the fetch [html_process_data()].
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Any stylesheets which the document depends on are fetched and parsed.
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The tree is converted to a 'box tree' by xml_to_box(). The box tree contains a
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node for each block, inline element, table, etc. The aim of this stage is to
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determine the 'display' or 'float' CSS property of each element, and create the
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corresponding node in the box tree. At this stage the style for each element is
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also calculated (from CSS rules and element attributes). The tree is normalised
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so that each node only has children of permitted types (eg. TABLE_CELLs must be
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within TABLE_ROWs) by adding missing boxes.
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The box tree is passed to the layout engine [layout_document()], which finds the
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space required by each element and assigns coordinates to the boxes, based on
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the style of each element and the available width. This includes formatting
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inline elements into lines, laying out tables, and positioning floats. The
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layout engine can be invoked again on a already laid out box tree to reformat it
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to a new width. Coordinates in the box tree are relative to the position of the
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parent node.
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The box tree can then be rendered using each node's coordinates.
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box.[ch] -- definition of the box tree, conversion from xml tree, normalising
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html.[ch] -- interface to HTML processing
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layout.[ch] -- layout engine
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________________________________________________________________________________
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Specifications
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HTML 4.01 http://www.w3.org/TR/html401/
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XHTML 1.0 http://www.w3.org/TR/xhtml1/
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CSS2 http://www.w3.org/TR/REC-CSS2/
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HTTP/1.1 http://www.w3.org/Protocols/rfc2616/rfc2616.html
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PNG http://www.w3.org/Graphics/PNG/
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________________________________________________________________________________
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Libraries
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Get these compiled for RISC OS with headers from
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http://netsurf.strcprstskrzkrk.co.uk/developer/
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libxml (XML and HTML parser) http://xmlsoft.org/
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libcurl (HTTP, FTP, etc) http://curl.haxx.se/libcurl/
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OSLib (C interface to RISC OS SWIs) http://ro-oslib.sourceforge.net/
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libutf-8 http://www.whizkidtech.redprince.net/i18n/
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________________________________________________________________________________
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