CSS Modularization (CSS3) (Dynamic HTML: The Definitive Reference, 2nd Edition)

Dynamic HTML: The Definitive Reference, 2rd Ed.

7.3. CSS Modularization (CSS3)

In the draft stages of CSS modularization, the effort appears to focus on not only a division of CSS attributes into logical groups, but also on a division of labor. With modularization, pieces of the standard, such as specifications for selectors, value types, and content models (box and line models, for example), can be developed individually. Implementation reasons still apply to the impetus behind the move toward modularization. A browser intended for visual display of content, for instance, shouldn't be expected to include style sheet attributes for aural styles.

Table 7-2 presents a preliminary list of modules that may comprise CSS3. Several categories in this list are new to CSS, rather than simply reorganized CSS2 features. Even if not every module is complete when other CSS3 modules are firmed up, others can be added as they are ready.

Table 7-2. Preliminary CSS3 modules

Module	Description
Selectors	Selector types and specificity
Values and units	Value types (e.g., lengths, colors) and their representation
Value assignment, cascade, and inheritance	How styles impact elements (e.g., specified versus computed values), cascading rules, attribute inheritance chains
Box model/vertical	Block layout: borders, margins, padding, overflow, clipping, and visibility
Positioning	Positioning, floating layout
Color/gamma/color profiles	Foreground color, gamma correction
Colors and Backgrounds	Background images and colors
Line box model	Inline element rendering
Text/bidi/vertical alignment	Text decoration, line height, spacing, transforms, and alignment
Fonts	Font-related attributes
Ruby	CSS-based ruby text attributes
Generated content/markers	List styles, automatic counters, `:before` and `:after` pseudo-elements
Replaced content	Replaced content attributes
Paged media	Page breaks, running headers and footers, cross-reference pointers
User interface	Form element styles, cursors, kiosk mode display
WebFonts	Web-enhanced font attributes
ACSS	Aural styles and accessibility enhancements
SMIL	CSS connection to Synchronized Multimedia standards
Tables	Table-related attributes
Columns	Multi-column layout
SVG	CSS connection to Scalable Vector Graphics standard
Math	Rendering math expressions (Math Markup Language standard)
BECSS	Scripted behaviors extension
Media queries	Applying styles based on quantitative features supported by media (e.g., screen size)
Syntax/grammar	Basic syntax, including namespaces
Test suite	Specific examples and guidelines

Several CSS3 modules listed in Table 7-2 either represent entirely new CSS features or include expanded features of existing CSS2 areas. The list is also ambitious in that a few modules point to W3C work that is far from finished.