style/values/computed/
position.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! CSS handling for the computed value of
6//! [`position`][position] values.
7//!
8//! [position]: https://drafts.csswg.org/css-backgrounds-3/#position
9
10use crate::values::computed::{
11    Context, Integer, LengthPercentage, NonNegativeNumber, Percentage, ToComputedValue,
12};
13use crate::values::generics::position::Position as GenericPosition;
14use crate::values::generics::position::PositionComponent as GenericPositionComponent;
15use crate::values::generics::position::PositionOrAuto as GenericPositionOrAuto;
16use crate::values::generics::position::ZIndex as GenericZIndex;
17use crate::values::generics::position::{
18    AnchorSideKeyword, GenericAnchorFunction, GenericAnchorSide,
19};
20use crate::values::generics::position::{AspectRatio as GenericAspectRatio, GenericInset};
21pub use crate::values::specified::position::{
22    AnchorName, AnchorScope, DashedIdentAndOrTryTactic, PositionAnchor, PositionArea,
23    PositionAreaKeyword, PositionAreaType, PositionTryFallbacks, PositionTryOrder,
24    PositionVisibility,
25};
26pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
27use crate::Zero;
28use std::fmt::{self, Write};
29use style_traits::{CssWriter, ToCss};
30
31/// The computed value of a CSS `<position>`
32pub type Position = GenericPosition<HorizontalPosition, VerticalPosition>;
33
34/// The computed value of an `auto | <position>`
35pub type PositionOrAuto = GenericPositionOrAuto<Position>;
36
37/// The computed value of a CSS horizontal position.
38pub type HorizontalPosition = LengthPercentage;
39
40/// The computed value of a CSS vertical position.
41pub type VerticalPosition = LengthPercentage;
42
43/// The computed value of anchor side.
44pub type AnchorSide = GenericAnchorSide<Percentage>;
45
46impl AnchorSide {
47    /// Break down given anchor side into its equivalent keyword and percentage.
48    pub fn keyword_and_percentage(&self) -> (AnchorSideKeyword, Percentage) {
49        match self {
50            Self::Percentage(p) => (AnchorSideKeyword::Start, *p),
51            Self::Keyword(k) => {
52                if matches!(k, AnchorSideKeyword::Center) {
53                    (AnchorSideKeyword::Start, Percentage(0.5))
54                } else {
55                    (*k, Percentage::zero())
56                }
57            },
58        }
59    }
60}
61
62/// The computed value of an `anchor()` function.
63pub type AnchorFunction = GenericAnchorFunction<Percentage, Inset>;
64
65#[cfg(feature = "gecko")]
66use crate::{
67    gecko_bindings::structs::AnchorPosOffsetResolutionParams,
68    logical_geometry::PhysicalSide,
69    values::{computed::Length, DashedIdent},
70};
71
72impl AnchorFunction {
73    /// Resolve the anchor function with the given resolver. Returns `Err()` if no anchor is found.
74    #[cfg(feature = "gecko")]
75    pub fn resolve(
76        anchor_name: &DashedIdent,
77        anchor_side: &AnchorSide,
78        prop_side: PhysicalSide,
79        params: &AnchorPosOffsetResolutionParams,
80    ) -> Result<Length, ()> {
81        use crate::gecko_bindings::structs::Gecko_GetAnchorPosOffset;
82
83        let (keyword, percentage) = anchor_side.keyword_and_percentage();
84        let mut offset = Length::zero();
85        let valid = unsafe {
86            Gecko_GetAnchorPosOffset(
87                params,
88                anchor_name.0.as_ptr(),
89                prop_side as u8,
90                keyword as u8,
91                percentage.0,
92                &mut offset,
93            )
94        };
95
96        if !valid {
97            return Err(());
98        }
99
100        Ok(offset)
101    }
102}
103
104/// A computed type for `inset` properties.
105pub type Inset = GenericInset<Percentage, LengthPercentage>;
106
107impl Position {
108    /// `50% 50%`
109    #[inline]
110    pub fn center() -> Self {
111        Self::new(
112            LengthPercentage::new_percent(Percentage(0.5)),
113            LengthPercentage::new_percent(Percentage(0.5)),
114        )
115    }
116
117    /// `0% 0%`
118    #[inline]
119    pub fn zero() -> Self {
120        Self::new(LengthPercentage::zero(), LengthPercentage::zero())
121    }
122}
123
124impl ToCss for Position {
125    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
126    where
127        W: Write,
128    {
129        self.horizontal.to_css(dest)?;
130        dest.write_char(' ')?;
131        self.vertical.to_css(dest)
132    }
133}
134
135impl GenericPositionComponent for LengthPercentage {
136    fn is_center(&self) -> bool {
137        match self.to_percentage() {
138            Some(Percentage(per)) => per == 0.5,
139            _ => false,
140        }
141    }
142}
143
144#[inline]
145fn block_or_inline_to_inferred(keyword: PositionAreaKeyword) -> PositionAreaKeyword {
146    match keyword {
147        PositionAreaKeyword::BlockStart | PositionAreaKeyword::InlineStart => {
148            PositionAreaKeyword::Start
149        },
150        PositionAreaKeyword::BlockEnd | PositionAreaKeyword::InlineEnd => PositionAreaKeyword::End,
151        PositionAreaKeyword::SpanBlockStart | PositionAreaKeyword::SpanInlineStart => {
152            PositionAreaKeyword::SpanStart
153        },
154        PositionAreaKeyword::SpanBlockEnd | PositionAreaKeyword::SpanInlineEnd => {
155            PositionAreaKeyword::SpanEnd
156        },
157        PositionAreaKeyword::SelfBlockStart | PositionAreaKeyword::SelfInlineStart => {
158            PositionAreaKeyword::SelfStart
159        },
160        PositionAreaKeyword::SelfBlockEnd | PositionAreaKeyword::SelfInlineEnd => {
161            PositionAreaKeyword::SelfEnd
162        },
163        PositionAreaKeyword::SpanSelfBlockStart | PositionAreaKeyword::SpanSelfInlineStart => {
164            PositionAreaKeyword::SpanSelfStart
165        },
166        PositionAreaKeyword::SpanSelfBlockEnd | PositionAreaKeyword::SpanSelfInlineEnd => {
167            PositionAreaKeyword::SpanSelfEnd
168        },
169        other => other,
170    }
171}
172
173#[inline]
174fn inferred_to_block(keyword: PositionAreaKeyword) -> PositionAreaKeyword {
175    match keyword {
176        PositionAreaKeyword::Start => PositionAreaKeyword::BlockStart,
177        PositionAreaKeyword::End => PositionAreaKeyword::BlockEnd,
178        PositionAreaKeyword::SpanStart => PositionAreaKeyword::SpanBlockStart,
179        PositionAreaKeyword::SpanEnd => PositionAreaKeyword::SpanBlockEnd,
180        PositionAreaKeyword::SelfStart => PositionAreaKeyword::SelfBlockStart,
181        PositionAreaKeyword::SelfEnd => PositionAreaKeyword::SelfBlockEnd,
182        PositionAreaKeyword::SpanSelfStart => PositionAreaKeyword::SpanSelfBlockStart,
183        PositionAreaKeyword::SpanSelfEnd => PositionAreaKeyword::SpanSelfBlockEnd,
184        other => other,
185    }
186}
187
188#[inline]
189fn inferred_to_inline(keyword: PositionAreaKeyword) -> PositionAreaKeyword {
190    match keyword {
191        PositionAreaKeyword::Start => PositionAreaKeyword::InlineStart,
192        PositionAreaKeyword::End => PositionAreaKeyword::InlineEnd,
193        PositionAreaKeyword::SpanStart => PositionAreaKeyword::SpanInlineStart,
194        PositionAreaKeyword::SpanEnd => PositionAreaKeyword::SpanInlineEnd,
195        PositionAreaKeyword::SelfStart => PositionAreaKeyword::SelfInlineStart,
196        PositionAreaKeyword::SelfEnd => PositionAreaKeyword::SelfInlineEnd,
197        PositionAreaKeyword::SpanSelfStart => PositionAreaKeyword::SpanSelfInlineStart,
198        PositionAreaKeyword::SpanSelfEnd => PositionAreaKeyword::SpanSelfInlineEnd,
199        other => other,
200    }
201}
202
203// This exists because the spec currently says that further simplifications
204// should be made to the computed value. That's confusing though, and probably
205// all these simplifications should be wrapped up into the simplifications that
206// we make to the specified value. I.e. all this should happen in
207// PositionArea::parse_internal().
208// See also https://github.com/w3c/csswg-drafts/issues/12759
209impl ToComputedValue for PositionArea {
210    type ComputedValue = PositionArea;
211
212    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
213        let mut computed = self.clone();
214
215        let pair_type = self.get_type();
216
217        if pair_type == PositionAreaType::Logical || pair_type == PositionAreaType::SelfLogical {
218            if computed.second != PositionAreaKeyword::None {
219                computed.first = block_or_inline_to_inferred(computed.first);
220                computed.second = block_or_inline_to_inferred(computed.second);
221            }
222        } else if pair_type == PositionAreaType::Inferred
223            || pair_type == PositionAreaType::SelfInferred
224        {
225            if computed.second == PositionAreaKeyword::SpanAll {
226                // We remove the superfluous span-all, converting the inferred
227                // keyword to a logical keyword to avoid ambiguity, per spec.
228                computed.first = inferred_to_block(computed.first);
229                computed.second = PositionAreaKeyword::None;
230            } else if computed.first == PositionAreaKeyword::SpanAll {
231                computed.first = computed.second;
232                computed.first = inferred_to_inline(computed.first);
233                computed.second = PositionAreaKeyword::None;
234            }
235        }
236
237        if computed.first == computed.second {
238            computed.second = PositionAreaKeyword::None;
239        }
240
241        computed
242    }
243
244    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
245        computed.clone()
246    }
247}
248
249/// A computed value for the `z-index` property.
250pub type ZIndex = GenericZIndex<Integer>;
251
252/// A computed value for the `aspect-ratio` property.
253pub type AspectRatio = GenericAspectRatio<NonNegativeNumber>;
style/values/computed/position.rs

style/values/computed/
position.rs
