From abd76d327e00fd991488f248e66faa33e0b78c2d Mon Sep 17 00:00:00 2001 From: Michael Drake Date: Mon, 27 Jul 2009 14:39:33 +0000 Subject: Delete old CSS document, because it's out-of-date. Should we move the other docs to the wiki? svn path=/trunk/netsurf/; revision=8823 --- Docs/03-css | 81 ------------------------------------------------------------- 1 file changed, 81 deletions(-) delete mode 100644 Docs/03-css (limited to 'Docs') diff --git a/Docs/03-css b/Docs/03-css deleted file mode 100644 index 5744e27b7..000000000 --- a/Docs/03-css +++ /dev/null @@ -1,81 +0,0 @@ -CSS parser -========== - -CSS is tokenised by a re2c-generated scanner (scanner.l), and then parsed into a -memory representation by a lemon-generated parser (parser.y, ruleset.c). - -Styles are retrieved using css_get_style(). They can be cascaded by -css_cascade(). - -Implementing a new CSS property -------------------------------- -In this section I go through adding a CSS property to NetSurf, using the -'white-space' property as an example. -- James Bursa - -First read and understand the description of the property in the CSS -specification (I have worked from CSS 2, but now 2.1 is probably better). - -Add the property to css_enums. This file is used to generate css_enum.h and -css_enum.c: - - css_white_space inherit normal nowrap pre - -(I'm not doing pre-wrap and pre-line for now.) - -Add fields to struct css_style to represent the property: - - css_white_space white_space; - -Add a parser function for the property to ruleset.c. Declare a new function: - - static void parse_white_space(struct css_style * const s, const struct css_node * const v); - -and add it to property_table: - - { "white-space", parse_white_space }, - -This will cause the function to be called when the parser comes to a rule giving -a value for white-space. The function is passed a linked list of struct -::css_node, each of which corresponds to a token in the CSS source, and must -update s to correspond to that rule. For white-space, the implementation is -simply: - - void parse_white_space(struct css_style * const s, const struct css_node * const v) - { - css_white_space z; - if (v->type != CSS_NODE_IDENT || v->next != 0) - return; - z = css_white_space_parse(v->data, v->data_length); - if (z != CSS_WHITE_SPACE_UNKNOWN) - s->white_space = z; - } - -First we check that the value consists of exactly one identifier, as described -in the specification. If it is not, we ignore it, since it may be some future -CSS. The css_white_space_parse() function is generated in css_enum.c, and -converts a string giving a value to a constant. If the conversion succeeds, the -style s is updated. - -Add defaults for the style to css_base_style, css_empty_style, and -css_blank_style in css.c. The value in css_base_style should be the one given as -'Initial' in the spec, and the value in css_empty_style should be inherit. If -'Inherited' is yes in the spec, the value in css_blank_style should be inherit, -otherwise it should be the one given as 'Initial'. Thus for white-space, which -has "Initial: normal, Inherited: yes" in the spec, we use CSS_WHITE_SPACE_NORMAL -in css_base_style and CSS_WHITE_SPACE_INHERIT in the other two. - -Edit css_cascade() and css_merge() in css.c to handle the property. In both -cases for white-space this looks like: - - if (apply->white_space != CSS_WHITE_SPACE_INHERIT) - style->white_space = apply->white_space; - -Add the property to css_dump_style() (not essential). - -Now the box, layout and / or redraw code needs to be changed to use the new -style property. This varies much more depending on the property. - -For white-space, convert_xml_to_box() was changed to split text at newlines if -white-space was pre, and to replace spaces with hard spaces for nowrap. -Additionally, calculate_inline_container_widths() was changed to give the -appropriate minimum width for pre and nowrap. -- cgit v1.2.3