style: Serialize a bunch of image properties with Servo.

I had to fix the conversion for BackgroundSize too, hopefully we can
simplify all this using cbindgen in the future instead of CalcValue.

Differential Revision: https://phabricator.services.mozilla.com/D7580

components/style/gecko/conversions.rs

@@ -17,7 +17,7 @@ use gecko_bindings::sugar::ns_style_coord::{CoordData, CoordDataMut, CoordDataVa
 use std::f32::consts::PI;
 use stylesheets::{Origin, RulesMutateError};
 use values::computed::{Angle, CalcLengthOrPercentage, Gradient, Image};
-use values::computed::{Integer, LengthOrPercentage, LengthOrPercentageOrAuto};
+use values::computed::{Integer, LengthOrPercentage, LengthOrPercentageOrAuto, NonNegativeLengthOrPercentageOrAuto};
 use values::computed::{Percentage, TextAlign};
 use values::computed::image::LineDirection;
 use values::computed::url::ComputedImageUrl;
@@ -106,6 +106,26 @@ impl From<nsStyleCoord_CalcValue> for LengthOrPercentageOrAuto {
     }
 }
 
+// FIXME(emilio): A lot of these impl From should probably become explicit or
+// disappear as we move more stuff to cbindgen.
+impl From<nsStyleCoord_CalcValue> for NonNegativeLengthOrPercentageOrAuto {
+    fn from(other: nsStyleCoord_CalcValue) -> Self {
+        use values::generics::NonNegative;
+        use style_traits::values::specified::AllowedNumericType;
+        NonNegative(if other.mLength < 0 || other.mPercent < 0. {
+            LengthOrPercentageOrAuto::Calc(
+                CalcLengthOrPercentage::with_clamping_mode(
+                    Au(other.mLength).into(),
+                    if other.mHasPercent { Some(Percentage(other.mPercent)) } else { None },
+                    AllowedNumericType::NonNegative,
+                )
+            )
+        } else {
+            other.into()
+        })
+    }
+}
+
 impl From<Angle> for CoordDataValue {
     fn from(reference: Angle) -> Self {
         match reference {

components/style/gecko/url.rs

@@ -273,14 +273,18 @@ impl ToComputedValue for SpecifiedImageUrl {
     }
 }
 
-fn serialize_computed_url<W>(url_value_data: &URLValueData, dest: &mut CssWriter<W>) -> fmt::Result
+fn serialize_computed_url<W>(
+    url_value_data: &URLValueData,
+    dest: &mut CssWriter<W>,
+    get_url: unsafe extern "C" fn(*const URLValueData, *mut nsCString) -> (),
+) -> fmt::Result
 where
     W: Write,
 {
     dest.write_str("url(")?;
     unsafe {
         let mut string = nsCString::new();
-        bindings::Gecko_GetComputedURLSpec(url_value_data, &mut string);
+        get_url(url_value_data, &mut string);
         string.as_str_unchecked().to_css(dest)?;
     }
     dest.write_char(')')
@@ -298,7 +302,11 @@ impl ToCss for ComputedUrl {
     where
         W: Write,
     {
-        serialize_computed_url(&self.0.url_value._base, dest)
+        serialize_computed_url(
+            &self.0.url_value._base,
+            dest,
+            bindings::Gecko_GetComputedURLSpec,
+        )
     }
 }
 
@@ -319,7 +327,11 @@ impl ToCss for ComputedImageUrl {
     where
         W: Write,
     {
-        serialize_computed_url(&self.0.image_value._base, dest)
+        serialize_computed_url(
+            &self.0.image_value._base,
+            dest,
+            bindings::Gecko_GetComputedImageURLSpec,
+        )
     }
 }
 

components/style/properties/gecko.mako.rs

@@ -4005,7 +4005,6 @@ fn static_assert() {
     pub fn clone_${shorthand}_size(&self) -> longhands::${shorthand}_size::computed_value::T {
         use gecko_bindings::structs::nsStyleCoord_CalcValue as CalcValue;
         use gecko_bindings::structs::nsStyleImageLayers_Size_DimensionType as DimensionType;
-        use values::generics::NonNegative;
         use values::computed::NonNegativeLengthOrPercentageOrAuto;
         use values::generics::background::BackgroundSize;
 
@@ -4014,7 +4013,7 @@ fn static_assert() {
                 NonNegativeLengthOrPercentageOrAuto::auto()
             } else {
                 debug_assert_eq!(ty, DimensionType::eLengthPercentage as u8);
-                NonNegative(value.into())
+                value.into()
             }
         }
 

components/style/values/computed/length.rs

@@ -202,21 +202,34 @@ impl ToCss for CalcLengthOrPercentage {
     {
         use num_traits::Zero;
 
-        let (length, percentage) = match (self.length, self.percentage) {
-            (l, None) => return l.to_css(dest),
-            (l, Some(p)) if l.px() == 0. => return p.to_css(dest),
-            (l, Some(p)) => (l, p),
-        };
+        let length = self.unclamped_length();
+        match self.percentage {
+            Some(p) => {
+                if length.px() == 0. && self.clamping_mode.clamp(p.0) == p.0 {
+                    return p.to_css(dest);
+                }
+            }
+            None => {
+                if self.clamping_mode.clamp(length.px()) == length.px() {
+                    return length.to_css(dest);
+                }
+            }
+        }
 
         dest.write_str("calc(")?;
-        percentage.to_css(dest)?;
-
-        dest.write_str(if length.px() < Zero::zero() {
-            " - "
+        if let Some(percentage) = self.percentage {
+            percentage.to_css(dest)?;
+            if length.px() != 0. {
+                dest.write_str(if length.px() < Zero::zero() {
+                    " - "
+                } else {
+                    " + "
+                })?;
+                length.abs().to_css(dest)?;
+            }
         } else {
-            " + "
-        })?;
-        length.abs().to_css(dest)?;
+            length.to_css(dest)?;
+        }
 
         dest.write_str(")")
     }