style: Implement the CSS line-break property, with values "auto | anywhere".

Note that the "loose | normal | strict" values are not yet parsed/implemented.

Differential Revision: https://phabricator.services.mozilla.com/D29817

components/style/properties/data.py

@@ -325,6 +325,7 @@ class Longhand(object):
                 "JustifyContent",
                 "JustifyItems",
                 "JustifySelf",
+                "LineBreak",
                 "MozForceBrokenImageIcon",
                 "MozListReversed",
                 "MozScriptLevel",

components/style/properties/longhands/inherited_text.mako.rs

@@ -264,6 +264,16 @@ ${helpers.predefined_type(
     spec="https://drafts.csswg.org/css-text-3/#tab-size-property",
 )}
 
+${helpers.predefined_type(
+    "line-break",
+    "LineBreak",
+    "computed::LineBreak::Auto",
+    products="gecko",
+    animation_value_type="discrete",
+    spec="https://drafts.csswg.org/css-text-3/#line-break-property",
+    needs_context=False,
+)}
+
 // CSS Compatibility
 // https://compat.spec.whatwg.org
 ${helpers.predefined_type(

components/style/values/computed/mod.rs

@@ -77,7 +77,7 @@ pub use self::svg::MozContextProperties;
 pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
 pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::table::XSpan;
-pub use self::text::{InitialLetter, LetterSpacing, LineHeight};
+pub use self::text::{InitialLetter, LetterSpacing, LineBreak, LineHeight};
 pub use self::text::{OverflowWrap, TextOverflow, WordBreak, WordSpacing};
 pub use self::text::{TextAlign, TextEmphasisPosition, TextEmphasisStyle};
 pub use self::time::Time;

components/style/values/computed/text.rs

@@ -20,7 +20,7 @@ use style_traits::{CssWriter, ToCss};
 
 pub use crate::values::specified::TextAlignKeyword as TextAlign;
 pub use crate::values::specified::TextTransform;
-pub use crate::values::specified::{OverflowWrap, WordBreak};
+pub use crate::values::specified::{LineBreak, OverflowWrap, WordBreak};
 pub use crate::values::specified::{TextDecorationLine, TextEmphasisPosition};
 
 /// A computed value for the `initial-letter` property.

components/style/values/specified/mod.rs

@@ -81,7 +81,7 @@ pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::svg_path::SVGPathData;
 pub use self::table::XSpan;
 pub use self::text::TextTransform;
-pub use self::text::{InitialLetter, LetterSpacing, LineHeight, TextAlign};
+pub use self::text::{InitialLetter, LetterSpacing, LineBreak, LineHeight, TextAlign};
 pub use self::text::{OverflowWrap, TextEmphasisPosition, TextEmphasisStyle, WordBreak};
 pub use self::text::{TextAlignKeyword, TextDecorationLine, TextOverflow, WordSpacing};
 pub use self::time::Time;

components/style/values/specified/text.rs

@@ -1005,6 +1005,32 @@ pub enum WordBreak {
     BreakWord,
 }
 
+/// Values for the `line-break` property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum LineBreak {
+    Auto,
+    /// TODO: additional values not yet implemented
+    /// Loose,
+    /// Normal,
+    /// Strict,
+    Anywhere,
+}
+
 /// Values for the `overflow-wrap` property.
 #[repr(u8)]
 #[derive(