Make style system support mozmm unit and compute it correctly.

MozReview-Commit-ID: hCUs8xuNd1

components/style/values/computed/length.rs

@@ -29,7 +29,10 @@ impl ToComputedValue for specified::NoCalcLength {
             specified::NoCalcLength::ViewportPercentage(length) =>
                 length.to_computed_value(context.viewport_size()),
             specified::NoCalcLength::ServoCharacterWidth(length) =>
-                length.to_computed_value(context.style().get_font().clone_font_size())
+                length.to_computed_value(context.style().get_font().clone_font_size()),
+            #[cfg(feature = "gecko")]
+            specified::NoCalcLength::Physical(length) =>
+                length.to_computed_value(context),
         }
     }
 

components/style/values/specified/length.rs

@@ -333,6 +333,51 @@ impl Mul<CSSFloat> for AbsoluteLength {
     }
 }
 
+/// Represents a physical length (mozmm) based on DPI
+#[derive(Clone, PartialEq, Copy, Debug)]
+#[cfg(feature = "gecko")]
+pub struct PhysicalLength(pub CSSFloat);
+
+#[cfg(feature = "gecko")]
+impl PhysicalLength {
+    fn is_zero(&self) -> bool {
+        self.0 == 0.
+    }
+
+    /// Computes the given character width.
+    pub fn to_computed_value(&self, context: &Context) -> Au {
+        use gecko_bindings::bindings;
+        // Same as Gecko
+        const MM_PER_INCH: f32 = 25.4;
+
+        let physical_inch = unsafe {
+            let pres_context = &*context.device.pres_context;
+            bindings::Gecko_GetAppUnitsPerPhysicalInch(&pres_context)
+        };
+
+        let inch = self.0 / MM_PER_INCH;
+
+        to_au_round(inch, physical_inch as f32)
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl ToCss for PhysicalLength {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        write!(dest, "{}mozmm", self.0)
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl Mul<CSSFloat> for PhysicalLength {
+    type Output = PhysicalLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> PhysicalLength {
+        PhysicalLength(self.0 * scalar)
+    }
+}
+
 /// A `<length>` without taking `calc` expressions into account
 ///
 /// https://drafts.csswg.org/css-values/#lengths
@@ -359,6 +404,10 @@ pub enum NoCalcLength {
     /// This cannot be specified by the user directly and is only generated by
     /// `Stylist::synthesize_rules_for_legacy_attributes()`.
     ServoCharacterWidth(CharacterWidth),
+
+    /// A physical length (mozmm) based on DPI
+    #[cfg(feature = "gecko")]
+    Physical(PhysicalLength),
 }
 
 impl HasViewportPercentage for NoCalcLength {
@@ -378,6 +427,8 @@ impl ToCss for NoCalcLength {
             NoCalcLength::ViewportPercentage(length) => length.to_css(dest),
             /* This should only be reached from style dumping code */
             NoCalcLength::ServoCharacterWidth(CharacterWidth(i)) => write!(dest, "CharWidth({})", i),
+            #[cfg(feature = "gecko")]
+            NoCalcLength::Physical(length) => length.to_css(dest),
         }
     }
 }
@@ -392,6 +443,8 @@ impl Mul<CSSFloat> for NoCalcLength {
             NoCalcLength::FontRelative(v) => NoCalcLength::FontRelative(v * scalar),
             NoCalcLength::ViewportPercentage(v) => NoCalcLength::ViewportPercentage(v * scalar),
             NoCalcLength::ServoCharacterWidth(_) => panic!("Can't multiply ServoCharacterWidth!"),
+            #[cfg(feature = "gecko")]
+            NoCalcLength::Physical(v) => NoCalcLength::Physical(v * scalar),
         }
     }
 }
@@ -438,6 +491,8 @@ impl NoCalcLength {
                 }
                 Ok(NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vmax(value)))
             },
+            #[cfg(feature = "gecko")]
+            "mozmm" => Ok(NoCalcLength::Physical(PhysicalLength(value))),
             _ => Err(())
         }
     }
@@ -453,6 +508,8 @@ impl NoCalcLength {
     pub fn is_zero(&self) -> bool {
         match *self {
             NoCalcLength::Absolute(length) => length.is_zero(),
+            #[cfg(feature = "gecko")]
+            NoCalcLength::Physical(length) => length.is_zero(),
             _ => false
         }
     }

ports/geckolib/glue.rs

@@ -1539,7 +1539,7 @@ pub extern "C" fn Servo_DeclarationBlock_SetLengthValue(declarations:
                                                         unit: structs::nsCSSUnit) {
     use style::properties::{PropertyDeclaration, LonghandId};
     use style::properties::longhands::_moz_script_min_size::SpecifiedValue as MozScriptMinSize;
-    use style::values::specified::length::{AbsoluteLength, FontRelativeLength};
+    use style::values::specified::length::{AbsoluteLength, FontRelativeLength, PhysicalLength};
     use style::values::specified::length::{LengthOrPercentage, NoCalcLength};
 
     let long = get_longhand_from_id!(property);
@@ -1550,6 +1550,7 @@ pub extern "C" fn Servo_DeclarationBlock_SetLengthValue(declarations:
         structs::nsCSSUnit::eCSSUnit_Inch => NoCalcLength::Absolute(AbsoluteLength::In(value)),
         structs::nsCSSUnit::eCSSUnit_Centimeter => NoCalcLength::Absolute(AbsoluteLength::Cm(value)),
         structs::nsCSSUnit::eCSSUnit_Millimeter => NoCalcLength::Absolute(AbsoluteLength::Mm(value)),
+        structs::nsCSSUnit::eCSSUnit_PhysicalMillimeter => NoCalcLength::Physical(PhysicalLength(value)),
         structs::nsCSSUnit::eCSSUnit_Point => NoCalcLength::Absolute(AbsoluteLength::Pt(value)),
         structs::nsCSSUnit::eCSSUnit_Pica => NoCalcLength::Absolute(AbsoluteLength::Pc(value)),
         structs::nsCSSUnit::eCSSUnit_Quarter => NoCalcLength::Absolute(AbsoluteLength::Q(value)),
@@ -2220,4 +2221,3 @@ pub extern "C" fn Servo_StyleSet_ResolveForDeclarations(raw_data: RawServoStyleS
                                               parent_style,
                                               declarations.clone()).into_strong()
 }
-