Table of Contents

Class CssPropertyDefinition

Namespace
Egami.Css
Assembly
Egami.Css.dll

A longhand property the cascade knows: whether it inherits, its initial value, and optionally how to validate a value.

public sealed record CssPropertyDefinition : IEquatable<CssPropertyDefinition>
Inheritance
CssPropertyDefinition
Implements
Inherited Members

Examples

// The registry says which properties inherit and their initial values; consumers add their own.
CssPropertyRegistry registry = CssPropertyRegistry.CreateDefault();
registry.Register(new CssPropertyDefinition("fill", Inherited: true, InitialValue: "black")
{
    Validate = value => CssColor.TryParse(value, out _),
});
registry.RegisterShorthand(new CssShorthandDefinition("marker", ["marker-start", "marker-end"],
    value => [new CssDeclaration("marker-start", value), new CssDeclaration("marker-end", value)]));

CssStyleSheet userAgent = CssStyleSheet.Parse("rect { fill: gray }");
CssStyleSheet author = CssStyleSheet.Parse("""
    svg { --accent: teal; font: 12px sans-serif }
    .layer { fill: var(--accent) }
    #r { fill: inherit; opacity: 0.5 }
    """);
var cascade = new CssCascade(
    [(userAgent, CssOrigin.UserAgent), (author, CssOrigin.Author)],
    new CssCascadeOptions { Registry = registry, Media = new CssMediaContext { Width = 800 } });

// Cascade each element (presentation attributes as hints, the style attribute as inline style), then compute it
// from its parent's computed style.
CssComputedStyle rootStyle = cascade.Compute(cascade.Cascade(root), null);
CssComputedStyle groupStyle = cascade.Compute(cascade.Cascade(group), rootStyle);
CssCascadedStyle cascaded = cascade.Cascade(rect,
    presentationHints: [CssDeclaration.Create("fill", "red")],
    inlineStyle: CssDeclaration.ParseList("stroke: blue"));
CssComputedStyle style = cascade.Compute(cascaded, groupStyle);

cascaded.TryGetDeclaration("fill", out CssDeclaration? winner, out CssOrigin origin); // fill: inherit, Author
string? fill = style.GetValueText("fill");           // "teal": inherited, var() substituted
string? fontSize = style.GetValueText("font-size");  // "12px": from the font shorthand, inherited
if (style.TryGetValue("opacity", out IReadOnlyList<CssComponentValue>? opacity))
{
    // The consumer parses each property by its type.
}

Constructors

CssPropertyDefinition(string, bool, string?)

A longhand property the cascade knows: whether it inherits, its initial value, and optionally how to validate a value.

public CssPropertyDefinition(string Name, bool Inherited, string? InitialValue)

Parameters

Name string

The property name in lowercase.

Inherited bool

Whether the property inherits by default.

InitialValue string

The initial value as CSS text, or null for none.

Examples

// The registry says which properties inherit and their initial values; consumers add their own.
CssPropertyRegistry registry = CssPropertyRegistry.CreateDefault();
registry.Register(new CssPropertyDefinition("fill", Inherited: true, InitialValue: "black")
{
    Validate = value => CssColor.TryParse(value, out _),
});
registry.RegisterShorthand(new CssShorthandDefinition("marker", ["marker-start", "marker-end"],
    value => [new CssDeclaration("marker-start", value), new CssDeclaration("marker-end", value)]));

CssStyleSheet userAgent = CssStyleSheet.Parse("rect { fill: gray }");
CssStyleSheet author = CssStyleSheet.Parse("""
    svg { --accent: teal; font: 12px sans-serif }
    .layer { fill: var(--accent) }
    #r { fill: inherit; opacity: 0.5 }
    """);
var cascade = new CssCascade(
    [(userAgent, CssOrigin.UserAgent), (author, CssOrigin.Author)],
    new CssCascadeOptions { Registry = registry, Media = new CssMediaContext { Width = 800 } });

// Cascade each element (presentation attributes as hints, the style attribute as inline style), then compute it
// from its parent's computed style.
CssComputedStyle rootStyle = cascade.Compute(cascade.Cascade(root), null);
CssComputedStyle groupStyle = cascade.Compute(cascade.Cascade(group), rootStyle);
CssCascadedStyle cascaded = cascade.Cascade(rect,
    presentationHints: [CssDeclaration.Create("fill", "red")],
    inlineStyle: CssDeclaration.ParseList("stroke: blue"));
CssComputedStyle style = cascade.Compute(cascaded, groupStyle);

cascaded.TryGetDeclaration("fill", out CssDeclaration? winner, out CssOrigin origin); // fill: inherit, Author
string? fill = style.GetValueText("fill");           // "teal": inherited, var() substituted
string? fontSize = style.GetValueText("font-size");  // "12px": from the font shorthand, inherited
if (style.TryGetValue("opacity", out IReadOnlyList<CssComponentValue>? opacity))
{
    // The consumer parses each property by its type.
}

Properties

Inherited

Whether the property inherits by default.

public bool Inherited { get; init; }

Property Value

bool

InitialValue

The initial value as CSS text, or null for none.

public string? InitialValue { get; init; }

Property Value

string

Name

The property name in lowercase.

public string Name { get; init; }

Property Value

string

Validate

Gets a check of a value (without var() or CSS-wide keywords), or null to accept any value. A declaration that fails it is dropped while the cascade is built, as browsers drop invalid declarations, so an earlier valid one can win; after var() substitution a failing value makes the property invalid at computed-value time.

public Func<IReadOnlyList<CssComponentValue>, bool>? Validate { get; init; }

Property Value

Func<IReadOnlyList<CssComponentValue>, bool>
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