Quelle  position.rs

/* 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/. */

//! CSS handling for the computed value of
//! [`position`][position] values.
//!
//! [position]: https://drafts.csswg.org/css-backgrounds-3/#position

use crate::values::computed::{Integer, LengthPercentage, NonNegativeNumber, Percentage};
use crate::values::generics::position::GenericAnchorFunction;
use crate::values::generics::position::Position as GenericPosition;
use crate::values::generics::position::PositionComponent as GenericPositionComponent;
use crate::values::generics::position::PositionOrAuto as GenericPositionOrAuto;
use crate::values::generics::position::ZIndex as GenericZIndex;
use crate::values::generics::position::{AspectRatio as GenericAspectRatio, GenericInset};
pub use crate::values::specified::position::{
    AnchorName, AnchorScope, DashedIdentAndOrTryTactic, PositionAnchor, PositionArea,
    PositionAreaKeyword, PositionTryFallbacks, PositionTryOrder, PositionVisibility,
};
pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
use crate::Zero;
use std::fmt::{self, Write};
use style_traits::{CssWriter, ToCss};

/// The computed value of a CSS `<position>`
pub type Position = GenericPosition<HorizontalPosition, VerticalPosition>;

/// The computed value of an `auto | <position>`
pub type PositionOrAuto = GenericPositionOrAuto<Position>;

/// The computed value of a CSS horizontal position.
pub type HorizontalPosition = LengthPercentage;

/// The computed value of a CSS vertical position.
pub type VerticalPosition = LengthPercentage;

/// The computed value of an `anchor()` function.
pub type AnchorFunction = GenericAnchorFunction<Percentage, LengthPercentage>;

/// A computed type for `inset` properties.
pub type Inset = GenericInset<Percentage, LengthPercentage>;

impl Position {
    /// `50% 50%`
    #[inline]
    pub fn center() -> Self {
        Self::new(
            LengthPercentage::new_percent(Percentage(0.5)),
            LengthPercentage::new_percent(Percentage(0.5)),
        )
    }

    /// `0% 0%`
    #[inline]
    pub fn zero() -> Self {
        Self::new(LengthPercentage::zero(), LengthPercentage::zero())
    }
}

impl ToCss for Position {
    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    where
        W: Write,
    {
        self.horizontal.to_css(dest)?;
        dest.write_char(' ')?;
        self.vertical.to_css(dest)
    }
}

impl GenericPositionComponent for LengthPercentage {
    fn is_center(&self) -> bool {
        match self.to_percentage() {
            Some(Percentage(per)) => per == 0.5,
            _ => false,
        }
    }
}

/// A computed value for the `z-index` property.
pub type ZIndex = GenericZIndex<Integer>;

/// A computed value for the `aspect-ratio` property.
pub type AspectRatio = GenericAspectRatio<NonNegativeNumber>;