Struct style::values::computed::Context

pub struct Context<'a> {
    pub is_root_element: bool,
    pub builder: StyleBuilder<'a>,
    pub cached_system_font: Option<()>,
    pub font_metrics_provider: &'a FontMetricsProvider,
    pub in_media_query: bool,
    pub quirks_mode: QuirksMode,
    pub for_smil_animation: bool,
    pub for_non_inherited_property: Option<LonghandId>,
    pub rule_cache_conditions: RefCell<&'a mut RuleCacheConditions>,
}

A Context is all the data a specified value could ever need to compute itself and be transformed to a computed value.

Fields

is_root_element: bool

Whether the current element is the root element.

builder: StyleBuilder<'a>

Values accessed through this need to be in the properties "computed early": color, text-decoration, font-size, display, position, float, border-*-style, outline-style, font-family, writing-mode...

cached_system_font: Option<()>

A dummy option for servo so initializing a computed::Context isn't painful.

TODO(emilio): Make constructors for Context, and drop this.

font_metrics_provider: &'a FontMetricsProvider

A font metrics provider, used to access font metrics to implement font-relative units.

in_media_query: bool

Whether or not we are computing the media list in a media query

quirks_mode: QuirksMode

The quirks mode of this context.

for_smil_animation: bool

Whether this computation is being done for a SMIL animation.

This is used to allow certain properties to generate out-of-range values, which SMIL allows.

for_non_inherited_property: Option<LonghandId>

The property we are computing a value for, if it is a non-inherited property. None if we are computed a value for an inherited property or not computing for a property at all (e.g. in a media query evaluation).

rule_cache_conditions: RefCell<&'a mut RuleCacheConditions>

The conditions to cache a rule node on the rule cache.

FIXME(emilio): Drop the refcell.

Methods

impl<'a> Context<'a>

pub fn for_media_query_evaluation<F, R>(
    device: &Device,
    quirks_mode: QuirksMode,
    f: F
) -> R where
    F: FnOnce(&Context) -> R, 

Creates a suitable context for media query evaluation, in which font-relative units compute against the system_font, and executes f with it.

pub fn is_root_element(&self) -> bool

Whether the current element is the root element.

pub fn device(&self) -> &Device

The current device.

pub fn viewport_size_for_viewport_unit_resolution(&self) -> Size2D<Au>

The current viewport size, used to resolve viewport units.

pub fn default_style(&self) -> &ComputedValues

The default computed style we're getting our reset style from.

pub fn style(&self) -> &StyleBuilder

The current style.

pub fn maybe_zoom_text(&self, size: NonNegativeLength) -> NonNegativeLength

(Servo doesn't do text-zoom)