1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
Documentation for Developers
This document contains an overview of the code for NetSurf, and any other
information useful to developers.
________________________________________________________________________________
Source Code Overview
The source is split at top level as follows:
content -- fetching, caching, and converting content
desktop -- non-platform specific front-end
render -- HTML and CSS processing and layout
riscos -- RISC OS specific code
utils -- misc. useful functions
________________________________________________________________________________
HTML and CSS processing and layout
This is the process to render an HTML document:
First the HTML is parsed to a tree of xmlNodes using the HTML parser in libxml.
This happens simultaneously with the fetch [html_process_data()].
Any stylesheets which the document depends on are fetched and parsed.
The tree is converted to a 'box tree' by xml_to_box(). The box tree contains a
node for each block, inline element, table, etc. The aim of this stage is to
determine the 'display' or 'float' CSS property of each element, and create the
corresponding node in the box tree. At this stage the style for each element is
also calculated (from CSS rules and element attributes). The tree is normalised
so that each node only has children of permitted types (eg. TABLE_CELLs must be
within TABLE_ROWs) by adding missing boxes.
The box tree is passed to the layout engine [layout_document()], which finds the
space required by each element and assigns coordinates to the boxes, based on
the style of each element and the available width. This includes formatting
inline elements into lines, laying out tables, and positioning floats. The
layout engine can be invoked again on a already laid out box tree to reformat it
to a new width. Coordinates in the box tree are relative to the position of the
parent node.
The box tree can then be rendered using each node's coordinates.
box.[ch] -- definition of the box tree, conversion from xml tree, normalising
css* -- CSS parser and handler
html.[ch] -- interface to HTML processing
layout.[ch] -- layout engine
________________________________________________________________________________
Specifications
HTML 4.01 http://www.w3.org/TR/html401/
XHTML 1.0 http://www.w3.org/TR/xhtml1/
CSS2 http://www.w3.org/TR/REC-CSS2/
HTTP/1.1 http://www.w3.org/Protocols/rfc2616/rfc2616.html
PNG http://www.w3.org/Graphics/PNG/
________________________________________________________________________________
Libraries
libxml (XML and HTML parser) http://xmlsoft.org/
libcurl (HTTP, FTP, etc) http://curl.haxx.se/libcurl/
OSLib (C interface to RISC OS SWIs) http://ro-oslib.sourceforge.net/
________________________________________________________________________________
|
