Auto merge of #12826 - Manishearth:addref, r=emilio,bholley

Add safer bindings for dealing with owned Arcs over FFI

Not yet ready to land, since I need to implement the logic for borrowed refs too. Ready for review for the first part.

The corresponding gecko changes are at https://github.com/servo/gecko-dev/compare/crashfix...Manishearth:addref-borrow

(I'll upload them to the bug once the borrow stuff is done)
r? @bholley

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components/style/gecko_conversions.rs

@@ -6,10 +6,23 @@
 //! Ideally, it would be in geckolib itself, but coherence
 //! forces us to keep the traits and implementations here
 
+#![allow(unsafe_code)]
+
 use app_units::Au;
+use gecko_bindings::bindings::{RawServoStyleSheet, ServoComputedValues};
 use gecko_bindings::structs::nsStyleCoord_CalcValue;
+use gecko_bindings::sugar::refptr::HasArcFFI;
+use properties::ComputedValues;
+use stylesheets::Stylesheet;
 use values::computed::{CalcLengthOrPercentage, LengthOrPercentage};
 
+unsafe impl HasArcFFI for Stylesheet {
+    type FFIType = RawServoStyleSheet;
+}
+unsafe impl HasArcFFI for ComputedValues {
+    type FFIType = ServoComputedValues;
+}
+
 impl From<CalcLengthOrPercentage> for nsStyleCoord_CalcValue {
     fn from(other: CalcLengthOrPercentage) -> nsStyleCoord_CalcValue {
         let has_percentage = other.percentage.is_some();

components/style/gecko_glue.rs

@@ -1,65 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#![allow(unsafe_code)]
-
-use std::marker::PhantomData;
-use std::mem::{forget, transmute};
-use std::sync::Arc;
-
-pub struct ArcHelpers<GeckoType, ServoType> {
-    phantom1: PhantomData<GeckoType>,
-    phantom2: PhantomData<ServoType>,
-}
-
-impl<GeckoType, ServoType> ArcHelpers<GeckoType, ServoType> {
-    pub fn with<F, Output>(raw: *mut GeckoType, cb: F) -> Output
-                           where F: FnOnce(&Arc<ServoType>) -> Output {
-        debug_assert!(!raw.is_null());
-
-        let owned = unsafe { Self::into(raw) };
-        let result = cb(&owned);
-        forget(owned);
-        result
-    }
-
-    pub fn maybe_with<F, Output>(maybe_raw: *mut GeckoType, cb: F) -> Output
-                                 where F: FnOnce(Option<&Arc<ServoType>>) -> Output {
-        let owned = if maybe_raw.is_null() {
-            None
-        } else {
-            Some(unsafe { Self::into(maybe_raw) })
-        };
-
-        let result = cb(owned.as_ref());
-        forget(owned);
-
-        result
-    }
-
-    pub unsafe fn into(ptr: *mut GeckoType) -> Arc<ServoType> {
-        transmute(ptr)
-    }
-
-    pub fn from(owned: Arc<ServoType>) -> *mut GeckoType {
-        unsafe { transmute(owned) }
-    }
-
-    pub fn borrow<F, Output>(borrowed: &Arc<ServoType>, cb: F) -> Output
-        where F: FnOnce(&mut GeckoType) -> Output
-    {
-        let borrowed_gecko_type: *const &mut GeckoType =
-            unsafe { transmute(borrowed) };
-
-        unsafe { cb(*borrowed_gecko_type) }
-    }
-
-    pub unsafe fn addref(ptr: *mut GeckoType) {
-        Self::with(ptr, |arc| forget(arc.clone()));
-    }
-
-    pub unsafe fn release(ptr: *mut GeckoType) {
-        let _ = Self::into(ptr);
-    }
-}

components/style/lib.rs

@@ -83,7 +83,6 @@ pub mod element_state;
 pub mod error_reporting;
 pub mod font_face;
 #[cfg(feature = "gecko")] pub mod gecko_conversions;
-#[cfg(feature = "gecko")] pub mod gecko_glue;
 #[cfg(feature = "gecko")] pub mod gecko_selector_impl;
 #[cfg(feature = "gecko")] pub mod gecko_values;
 pub mod keyframes;

components/style/properties/gecko.mako.rs

@@ -24,10 +24,10 @@ use gecko_bindings::bindings::{Gecko_EnsureImageLayersLength, Gecko_CreateGradie
 use gecko_bindings::bindings::{Gecko_CopyImageValueFrom, Gecko_CopyFontFamilyFrom};
 use gecko_bindings::bindings::{Gecko_FontFamilyList_AppendGeneric, Gecko_FontFamilyList_AppendNamed};
 use gecko_bindings::bindings::{Gecko_FontFamilyList_Clear, Gecko_InitializeImageLayer};
-use gecko_bindings::bindings;
+use gecko_bindings::bindings::ServoComputedValuesBorrowed;
 use gecko_bindings::structs;
 use gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordData, CoordDataMut};
-use gecko_glue::ArcHelpers;
+use gecko_bindings::sugar::refptr::HasArcFFI;
 use gecko_values::{StyleCoordHelpers, GeckoStyleCoordConvertible, convert_nscolor_to_rgba};
 use gecko_values::convert_rgba_to_nscolor;
 use gecko_values::round_border_to_device_pixels;
@@ -1358,10 +1358,9 @@ fn static_assert() {
 <%def name="define_ffi_struct_accessor(style_struct)">
 #[no_mangle]
 #[allow(non_snake_case, unused_variables)]
-pub extern "C" fn Servo_GetStyle${style_struct.gecko_name}(computed_values: *mut bindings::ServoComputedValues)
+pub extern "C" fn Servo_GetStyle${style_struct.gecko_name}(computed_values: ServoComputedValuesBorrowed)
   -> *const ${style_struct.gecko_ffi_name} {
-    type Helpers = ArcHelpers<bindings::ServoComputedValues, ComputedValues>;
-    Helpers::with(computed_values, |values| values.get_${style_struct.name_lower}().get_gecko()
+    ComputedValues::with(computed_values, |values| values.get_${style_struct.name_lower}().get_gecko()
                                                 as *const ${style_struct.gecko_ffi_name})
 }
 </%def>

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

@@ -34,6 +34,7 @@ ${helpers.predefined_type("fill-opacity", "Opacity", "1.0",
                           products="gecko", animatable=False)}
 
 ${helpers.single_keyword("fill-rule", "nonzero evenodd",
+                         gecko_enum_prefix="StyleFillRule",
                          products="gecko", animatable=False)}
 
 ${helpers.single_keyword("shape-rendering",
@@ -57,5 +58,5 @@ ${helpers.predefined_type("stroke-opacity", "Opacity", "1.0",
 // Section 14 - Clipping, Masking and Compositing
 ${helpers.single_keyword("clip-rule", "nonzero evenodd",
                          products="gecko",
-                         gecko_constant_prefix="NS_STYLE_FILL_RULE",
+                         gecko_enum_prefix="StyleFillRule",
                          animatable=False)}