Factor out opacity property to use an Opacity type.

components/style/properties/longhand/effects.mako.rs

@@ -7,46 +7,9 @@
 // Box-shadow, etc.
 <% data.new_style_struct("Effects", inherited=False) %>
 
-<%helpers:longhand name="opacity">
-    use cssparser::ToCss;
-    use std::fmt;
-    use values::CSSFloat;
-
-    impl ToCss for SpecifiedValue {
-        fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-            self.0.to_css(dest)
-        }
-    }
-
-    #[derive(Debug, Clone, PartialEq, HeapSizeOf)]
-    pub struct SpecifiedValue(pub CSSFloat);
-    pub mod computed_value {
-        use values::CSSFloat;
-        pub type T = CSSFloat;
-    }
-    #[inline]
-    pub fn get_initial_value() -> computed_value::T {
-        1.0
-    }
-
-    impl ToComputedValue for SpecifiedValue {
-        type ComputedValue = computed_value::T;
-
-        #[inline]
-        fn to_computed_value<Cx: TContext>(&self, _context: &Cx) -> computed_value::T {
-            if self.0 < 0.0 {
-                0.0
-            } else if self.0 > 1.0 {
-                1.0
-            } else {
-                self.0
-            }
-        }
-    }
-    fn parse(_context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
-        specified::parse_number(input).map(SpecifiedValue)
-    }
-</%helpers:longhand>
+${helpers.predefined_type("opacity",
+                          "Opacity",
+                          "1.0")}
 
 <%helpers:longhand name="box-shadow">
     use cssparser::{self, ToCss};

components/style/values.rs

@@ -1475,6 +1475,36 @@ pub mod specified {
             write!(dest, "{}s", self.0)
         }
     }
+
+    #[derive(Clone, Copy, Debug, PartialEq, PartialOrd, HeapSizeOf)]
+    pub struct Opacity(pub CSSFloat);
+
+    impl Opacity {
+        pub fn parse(input: &mut Parser) -> Result<Opacity, ()> {
+            parse_number(input).map(Opacity)
+        }
+    }
+
+    impl ToComputedValue for Opacity {
+        type ComputedValue = CSSFloat;
+
+        #[inline]
+        fn to_computed_value<Cx: TContext>(&self, _: &Cx) -> CSSFloat {
+            if self.0 < 0.0 {
+                0.0
+            } else if self.0 > 1.0 {
+                1.0
+            } else {
+                self.0
+            }
+        }
+    }
+
+    impl ToCss for Opacity {
+        fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+            self.0.to_css(dest)
+        }
+    }
 }
 
 pub mod computed {
@@ -2087,4 +2117,5 @@ pub mod computed {
         }
     }
     pub type Length = Au;
+    pub type Opacity = CSSFloat;
 }

ports/geckolib/properties.mako.rs

@@ -295,7 +295,7 @@ impl Debug for ${style_struct.gecko_ffi_name} {
    # These are booleans.
    force_stub += ["page-break-after", "page-break-before"]
 
-   simple_types = []
+   simple_types = ["Opacity"]
 
    keyword_longhands = [x for x in longhands if x.keyword and not x.name in force_stub]
    simple_longhands = [x for x in longhands