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Add HTTP errata link. svn path=/import/netsurf/; revision=580
180 lines
7.7 KiB
Plaintext
180 lines
7.7 KiB
Plaintext
/** \mainpage NetSurf 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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\section overview Source Code Overview
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The source is split at top level as follows:
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- \ref content
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- \ref css
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- \ref render
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- Non-platform specific front-end (desktop/)
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- RISC OS specific code (riscos/)
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- Unix debug build specific code (debug/)
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- Misc. useful functions (utils/)
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\section content Fetching, caching, and converting content (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.
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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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\section css CSS parser and interfaces (css/)
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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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\section render HTML processing and layout (render/)
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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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\section links Other Documentation
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RISC OS specific protocols:
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- Plugin http://www.ecs.soton.ac.uk/~jmb202/riscos/acorn/funcspec.html
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http://www.ecs.soton.ac.uk/~jmb202/riscos/acorn/browse-plugins.html
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- URI http://www.ecs.soton.ac.uk/~jmb202/riscos/acorn/uri.html
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- URL http://www.vigay.com/inet/inet_url.html
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- Nested WIMP http://www.ecs.soton.ac.uk/~jmb202/riscos/acorn/nested.html
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Specifications:
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- HTML 4.01 http://www.w3.org/TR/html401/
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(see also http://www.w3.org/MarkUp/)
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- XHTML 1.0 http://www.w3.org/TR/xhtml1/
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- CSS 2.1 http://www.w3.org/TR/CSS21/
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- HTTP/1.1 http://www.w3.org/Protocols/rfc2616/rfc2616.html
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and errata http://purl.org/NET/http-errata
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(see also http://www.w3.org/Protocols/)
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- HTTP Authentication http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2617.html
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- PNG http://www.w3.org/Graphics/PNG/
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- URI http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2396.html
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(see also http://www.w3.org/Addressing/ and RFC 2616)
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- Cookies http://wp.netscape.com/newsref/std/cookie_spec.html and
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http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2109.html
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\section libs 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://www.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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- libpng (PNG support) http://www.libpng.org/pub/png/libpng.html
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- zlib http://www.gzip.org/zlib/
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- uri http://www.nongnu.org/uri/
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\section addcss Implementing a new CSS property
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In this section I go through adding a CSS property to NetSurf, using the
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'white-space' property as an example. -- James Bursa
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1. Read and understand the description of the property in the CSS specification
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(I have worked from CSS 2, but now 2.1 is probably better).
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These changes are required in the css directory:
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2. Add the property to css_enums. This file is used to generate css_enum.h
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and css_enum.c:
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\code css_white_space inherit normal nowrap pre \endcode
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(I'm not doing pre-wrap and pre-line for now.)
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3. Add fields to struct ::css_style to represent the property:
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\code css_white_space white_space; \endcode
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4. Add a parser function for the property to ruleset.c. Declare a new
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function:
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\code static void parse_white_space(struct css_style * const s, const struct css_node * const v); \endcode
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and add it to ::property_table:
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\code { "white-space", parse_white_space }, \endcode
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This will cause the function to be called when the parser comes to a rule
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giving a value for white-space. The function is passed a linked list of
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struct ::css_node, each of which corresponds to a token in the CSS source,
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and must update s to correspond to that rule. For white-space, the
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implementation is simply:
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\code
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void parse_white_space(struct css_style * const s, const struct css_node * const v)
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{
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css_white_space z;
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if (v->type != CSS_NODE_IDENT || v->next != 0)
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return;
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z = css_white_space_parse(v->data);
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if (z != CSS_WHITE_SPACE_UNKNOWN)
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s->white_space = z;
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}
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\endcode
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First we check that the value consists of exactly one identifier, as
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described in the specification. If it is not, we ignore it, since it may be
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some future CSS. The css_white_space_parse() function is generated in
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css_enum.c, and converts a string giving a value to a constant. If the
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conversion succeeds, the style s is updated.
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5. Add defaults for the style to ::css_base_style, ::css_empty_style, and
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::css_blank_style in css.c. The value in css_base_style should be the one
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given as 'Initial' in the spec, and the value in css_empty_style should be
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inherit. If 'Inherited' is yes in the spec, the value in css_blank_style
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should be inherit, otherwise it should be the one given as 'Initial'. Thus
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for white-space, which has "Initial: normal, Inherited: yes" in the spec, we
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use CSS_WHITE_SPACE_NORMAL in css_base_style and CSS_WHITE_SPACE_INHERIT in
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the other two.
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6. Edit css_cascade() and css_merge() in css.c to handle the property. In
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both cases for white-space this looks like:
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\code
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if (apply->white_space != CSS_WHITE_SPACE_INHERIT)
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style->white_space = apply->white_space;
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\endcode
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Add the property to css_dump_style() (not essential).
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Now the box, layout and / or redraw code needs to be changed to use the new
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style property. This varies much more depending on the property.
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For white-space, convert_xml_to_box() was changed to split text at newlines if
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white-space was pre, and to replace spaces with hard spaces for nowrap.
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Additionally, calculate_inline_container_widths() was changed to give the
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appropriate minimum width for pre and nowrap.
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*/
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