Quelle  media_features.rs   Sprache: Rust

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

//! Servo's media feature list and evaluator.

use crate::derives::*;
use crate::queries::feature::{AllowsRanges, Evaluator, FeatureFlags, QueryFeatureDescription};
use crate::queries::values::PrefersColorScheme;
use crate::values::computed::{CSSPixelLength, Context, Resolution};
use std::fmt::Debug;

/// https://drafts.csswg.org/mediaqueries-4/#width
fn eval_width(context: &Context) -> CSSPixelLength {
    CSSPixelLength::new(context.device().au_viewport_size().width.to_f32_px())
}

#[derive(Clone, Copy, Debug, FromPrimitive, Parse, ToCss)]
#[repr(u8)]
enum Scan {
    Progressive,
    Interlace,
}

/// https://drafts.csswg.org/mediaqueries-4/#scan
fn eval_scan(_: &Context, _: Option<Scan>) -> bool {
    // Since we doesn't support the 'tv' media type, the 'scan' feature never
    // matches.
    false
}

/// https://drafts.csswg.org/mediaqueries-4/#resolution
fn eval_resolution(context: &Context) -> Resolution {
    Resolution::from_dppx(context.device().device_pixel_ratio().0)
}

/// https://compat.spec.whatwg.org/#css-media-queries-webkit-device-pixel-ratio
fn eval_device_pixel_ratio(context: &Context) -> f32 {
    eval_resolution(context).dppx()
}

fn eval_prefers_color_scheme(context: &Context, query_value: Option<PrefersColorScheme>) -> bool {
    match query_value {
        Some(v) => context.device().color_scheme() == v,
        None => true,
    }
}

/// A list with all the media features that Servo supports.
pub static MEDIA_FEATURES: [QueryFeatureDescription; 6] = [
    feature!(
        atom!("width"),
        AllowsRanges::Yes,
        Evaluator::Length(eval_width),
        FeatureFlags::empty(),
    ),
    feature!(
        atom!("scan"),
        AllowsRanges::No,
        keyword_evaluator!(eval_scan, Scan),
        FeatureFlags::empty(),
    ),
    feature!(
        atom!("resolution"),
        AllowsRanges::Yes,
        Evaluator::Resolution(eval_resolution),
        FeatureFlags::empty(),
    ),
    feature!(
        atom!("device-pixel-ratio"),
        AllowsRanges::Yes,
        Evaluator::Float(eval_device_pixel_ratio),
        FeatureFlags::WEBKIT_PREFIX,
    ),
    feature!(
        atom!("-moz-device-pixel-ratio"),
        AllowsRanges::Yes,
        Evaluator::Float(eval_device_pixel_ratio),
        FeatureFlags::empty(),
    ),
    feature!(
        atom!("prefers-color-scheme"),
        AllowsRanges::No,
        keyword_evaluator!(eval_prefers_color_scheme, PrefersColorScheme),
        FeatureFlags::empty(),
    ),
];