Auto merge of #19101 - CYBAI:moz-script-level-out-of-mako, r=emilio

style: Move font -moz-script-level outside of mako

This is a sub-PR of #19015
r? emilio

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #19068 (github issue number if applicable).
- [x] These changes do not require tests because _____

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components/style/values/specified/font.rs

@@ -505,3 +505,41 @@ impl Parse for MozScriptMinSize {
         Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
     }
 }
+
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
+#[derive(Clone, Copy, Debug, PartialEq)]
+/// Changes the scriptlevel in effect for the children.
+/// Ref: https://wiki.mozilla.org/MathML:mstyle
+///
+/// The main effect of scriptlevel is to control the font size.
+/// https://www.w3.org/TR/MathML3/chapter3.html#presm.scriptlevel
+pub enum MozScriptLevel {
+    /// Change `font-size` relatively
+    Relative(i32),
+    /// Change `font-size` absolutely
+    Absolute(i32),
+    /// Change `font-size` automatically
+    Auto
+}
+
+impl ToCss for MozScriptLevel {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            MozScriptLevel::Auto => dest.write_str("auto"),
+            MozScriptLevel::Relative(rel) => rel.to_css(dest),
+            // can only be specified by pres attrs; should not
+            // serialize to anything else
+            MozScriptLevel::Absolute(_) => Ok(()),
+        }
+    }
+}
+
+impl Parse for MozScriptLevel {
+    fn parse<'i, 't>(_: &ParserContext, input: &mut Parser<'i, 't>) -> Result<MozScriptLevel, ParseError<'i>> {
+        if let Ok(i) = input.try(|i| i.expect_integer()) {
+            return Ok(MozScriptLevel::Relative(i))
+        }
+        input.expect_ident_matching("auto")?;
+        Ok(MozScriptLevel::Auto)
+    }
+}

components/style/values/specified/mod.rs

@@ -30,7 +30,7 @@ pub use self::align::{AlignItems, AlignJustifyContent, AlignJustifySelf, Justify
 pub use self::background::{BackgroundRepeat, BackgroundSize};
 pub use self::border::{BorderCornerRadius, BorderImageSlice, BorderImageWidth};
 pub use self::border::{BorderImageSideWidth, BorderRadius, BorderSideWidth, BorderSpacing};
-pub use self::font::{FontWeight, MozScriptMinSize, XTextZoom};
+pub use self::font::{FontWeight, MozScriptLevel, MozScriptMinSize, XTextZoom};
 pub use self::box_::{AnimationIterationCount, AnimationName, ScrollSnapType, VerticalAlign};
 pub use self::color::{Color, ColorPropertyValue, RGBAColor};
 pub use self::effects::{BoxShadow, Filter, SimpleShadow};