CSS Parser

Note: This CSS parser is not suited for production yet and the API will change in the future!

The aim of this module is to serve as an intermediate stage in graphics rendering by supporting CSS as styling language.

It parses a CSS file and returns a list of rules. These rules are sorted by their specificity, so the programmer only needs to implement a way to render the rules.

Acknowledgement: A lot of inpsiration (and some code) is taken from the V compiler.

Features

• 100% Written in V
• Parser can parse bootstrap.min.css without errors
• Parser and checker produce errors and warnings
• Rules are sorted by CSS Specificity
• Property validator (checker stage) can be embedded to handle custom properties

TODO

• Implement more properties, functions and CSS datatypes.
• CSS Animations, @keyframe rules
• CSS Variables, probably will have to rely on a combination using the DOM
• Optimizations: store rules in a B+ tree by specificity, merge styles etc.
• Minifier

Project structure

The css folder follows a similair directory structure as the V compiler.

The compiler stage is as follows: lexer produces tokens -> parser produces AST -> checker validates the AST and transforms it to usable structs and sumtypes.

Usage Example

Run the example:

v run examples/simple.v

If you are confused why the resulting color is red please referer to CSS specificity .

The properties folder also contains examples on how properties can be used.

Tests

Run all tests with v test . , the tests in css/gen should fail.

Runnining individual checks

v run css/parser/tests/test_program.v css/parser/tests/file.css

You can swap out 'parser' for 'checker'

API

Properties

A list of properties and their types. Some property names start with - , this means that all CSS properties with this ending have the same type.

See types.v and properties.v to see the exact specification of each struct/sumtype.

Type	Properties	Remarks
AlphaValue	'opacity'
Background	'background'	struct containing all background- properties
Border	'border'	struct containing all border- properties
BorderColors	'border-color'	struct containing all 4 colors for each border side, will be merged into Border
BorderRadius	'border-radius'	struct containing the radius for each corner, will be merged into Border
BorderStyles	'border-style'	struct containing all styles for each border, will be merged into Border
ColorValue	'accent-color', 'background-color', 'caret-color', 'color', 'column-rule-color', 'outline-color'	A sumtype representing a color value, each property ending with -color will be this type.
DimensionValue	'block-size', 'bottom', 'column-gap', 'flex-basis', 'height', 'inline-size', 'left','letter-spacing' 'line-height', 'max-height', 'max-width', 'min-height', 'min-width', 'order', 'orphans', 'perspective', 'right', 'row-gap', 'tab-size', 'text-indent', 'top', 'vertical-align', 'widows', 'width', 'word-spacing', 'z-index'	A sumtype representing properties/values that represent a dimension/length, e.g. 10px , or 50% .
Font	'font', 'font-family', 'font-size', 'font-stretch', 'font-weight'	struct containing all font- properties
FontFamily	'font-family'	will be merged into 'font'
FontStretch	'font-stretch'	a sumtype containing the possible font-stretch properties, will be merged into 'font'
FontWeight	'font-weight'	will be merged into 'font'
FlexBox	'flex'	struct containg all flex- properties.
FlexDirection	'flex-direction'	will be merged into 'flex'
FlexSize	'flex-grow', 'flex-shrink'	will be merged into 'flex'
FlexWrap	'flex-wrap'	A sumtype containg the possible flex-wrap types, will be merged into 'flex'
FourDimensions	'padding', 'margin', 'border-width'	A struct containing 4 DimensionValue fields for top, right, bottom and left
Gap	'gap'	A struct containing 'row-gap' and 'column-gap'
Image	'background-image'	A sumtype holding the different values for the image CSS datatype
Keyword	'align-content', 'align-items', 'align-self', 'all', 'appearance', 'backface-visibility', 'border-collapse', 'box-sizing', 'caption-side', 'clear', 'cursor', 'direction', 'display', 'empty-cells', 'float', 'forced-color-adjust', 'isolation', 'justify-content', 'justify-items', 'justify-self', 'mix-blend-mode', 'object-fit', 'overflow-x', 'overflow-y', 'pointer-events', 'position', 'print-color-adjust', 'resize', 'scroll-behavior', 'table-layout', 'text-align', 'text-align-last', 'text-justify', 'text-rendering', 'text-transform', 'text-wrap', 'touch-action', 'unicode-bidi', 'user-select', 'visibility', 'white-space', 'word-break', 'word-wrap', 'writing-mode'	A type alias for string representing a CSS keyword like inherit
Overflow	'overflow'	A struct containing the properties 'overflow-x' and 'overflow-y'
ShadowValue	'box-shadow', 'text-shadow'	A struct containing all properties for a CSS shadow
Text	'text'	A struct containing all text CSS properties, starting with text-
TextCombineUpright	'text-combine-upright'	See MDN reference here section about digits . Will be merged into Text
TextOverflow	'text-overflow'	Sumtype of Keyword and a string , the string type will represent the ellipsis text specified by the user, will be merged into Text

Functions

See functions.v for the exact specifications.

Type	Function	Remarks
Gradient	'linear-gradient', 'radial-gradient', 'repeating-linear-gradient', 'repeating-radial-gradient'	Used as datatype for each property that can have a gradient like 'background-image'
Url	'url', 'src'	The type of url is defined in the UrlKind enum

Datatypes

See datatypes.v for a representation of currently supported CSS Datatypes.