Also do the comperty comparison in C++

api/sixtyfps-cpp/include/sixtyfps_pathdata.h

@@ -37,6 +37,23 @@ public:
     {
     }
 
+    friend bool operator==(const PathData &a, const PathData &b) {
+        if (a.data.tag != b.data.tag)
+            return false;
+        switch (a.data.tag) {
+            case cbindgen_private::types::PathData::Tag::Elements:
+                return a.data.elements._0 == b.data.elements._0;
+            case cbindgen_private::types::PathData::Tag::Events:
+                return a.data.events._0 == b.data.events._0 && b.data.events._0 == b.data.events._0;
+            case cbindgen_private::types::PathData::Tag::None:
+                return true;
+        }
+    }
+    friend bool operator!=(const PathData &a, const PathData &b) {
+        return !(a == b);
+    }
+
+
 private:
     static SharedArray<PathElement> elements_from_array(const PathElement *firstElement,
                                                         size_t count)

api/sixtyfps-cpp/include/sixtyfps_properties.h

@@ -41,8 +41,10 @@ struct Property
 
     void set(const T &value) const
     {
-        this->value = value;
+        if (this->value != value) {
-        cbindgen_private::sixtyfps_property_set_changed(&inner, &this->value);
+            this->value = value;
+            cbindgen_private::sixtyfps_property_set_changed(&inner, &this->value);
+        }
     }
 
     const T &get() const

api/sixtyfps-cpp/include/sixtyfps_resource.h

@@ -17,12 +17,19 @@ namespace sixtyfps {
 struct Resource
 {
 public:
-    using Tag = cbindgen_private::types::Resource::Tag;
-
     Resource() : data(Data::None()) { }
     Resource(const SharedString &file_path) : data(Data::AbsoluteFilePath(file_path)) { }
 
+    friend bool operator==(const Resource &a, const Resource &b) {
+        return a.data == b.data;
+    }
+    friend bool operator!=(const Resource &a, const Resource &b) {
+        return a.data != b.data;
+    }
+
+
 private:
+    using Tag = cbindgen_private::types::Resource::Tag;
     using Data = cbindgen_private::types::Resource;
     Data data;
 };

api/sixtyfps-cpp/include/sixtyfps_sharedarray.h

@@ -10,6 +10,7 @@ LICENSE END */
 #pragma once
 #include "sixtyfps_sharedarray_internal.h"
 #include <atomic>
+#include <algorithm>
 
 namespace sixtyfps {
 
@@ -95,6 +96,16 @@ struct SharedArray
         inner->size++;
     }
 
+    friend bool operator==(const SharedArray &a, const SharedArray &b) {
+        if (a.size() != a.size())
+            return false;
+        return std::equal(a.cbegin(), a.cend(), b.cbegin());
+    }
+    friend bool operator!=(const SharedArray &a, const SharedArray &b) {
+        return !(a == b);
+    }
+
+
 private:
     void detach(std::size_t expected_capacity) {
         if (inner->refcount == 1 && expected_capacity <= inner->capacity) {
@@ -142,4 +153,15 @@ private:
     explicit SharedArray(SharedArrayHeader *inner) : inner(inner) {}
 #endif
 };
+
+template<typename T>
+bool operator==(cbindgen_private::Slice<T> a, cbindgen_private::Slice<T> b) {
+    if (a.len != b.len) return false;
+    return std::equal(a.ptr, a.ptr + a.len, b.ptr);
+}
+template<typename T>
+bool operator!=(cbindgen_private::Slice<T> a, cbindgen_private::Slice<T> b) {
+    return !(a != b);
+}
+
 }

sixtyfps_compiler/generator/cpp.rs

@@ -108,6 +108,7 @@ mod cpp_ast {
                         signature: f.signature.clone(),
                         is_constructor_or_destructor: f.is_constructor_or_destructor,
                         is_static: false,
+                        is_friend: false,
                         statements: f.statements.take(),
                         template_parameters: f.template_parameters.clone(),
                     }))
@@ -126,6 +127,7 @@ mod cpp_ast {
         /// The function does not have return type
         pub is_constructor_or_destructor: bool,
         pub is_static: bool,
+        pub is_friend: bool,
         /// The list of statement instead the function.  When None,  this is just a function
         /// declaration without the definition
         pub statements: Option<Vec<String>>,
@@ -142,6 +144,9 @@ mod cpp_ast {
             if self.is_static {
                 write!(f, "static ")?;
             }
+            if self.is_friend {
+                write!(f, "friend ")?;
+            }
             // all functions are inlines because we are in a header
             write!(f, "inline ")?;
             if !self.is_constructor_or_destructor {
@@ -540,9 +545,12 @@ fn generate_struct(
     fields: &BTreeMap<String, Type>,
     diag: &mut BuildDiagnostics,
 ) {
+    let mut operator_eq = String::new();
     let mut members = fields
         .iter()
         .map(|(name, t)| {
+            use std::fmt::Write;
+            write!(operator_eq, " && a.{0} == b.{0}", name).unwrap();
             (
                 Access::Public,
                 Declaration::Var(Var {
@@ -563,6 +571,26 @@ fn generate_struct(
         (Declaration::Var(a), Declaration::Var(b)) => a.name.cmp(&b.name),
         _ => unreachable!(),
     });
+    members.push((
+        Access::Public,
+        Declaration::Function(Function {
+            name: "operator==".to_owned(),
+            signature: format!("(const {0} &a, const {0} &b) -> bool", name),
+            is_friend: true,
+            statements: Some(vec![format!("return true{};", operator_eq)]),
+            ..Function::default()
+        }),
+    ));
+    members.push((
+        Access::Public,
+        Declaration::Function(Function {
+            name: "operator!=".to_owned(),
+            signature: format!("(const {0} &a, const {0} &b) -> bool", name),
+            is_friend: true,
+            statements: Some(vec!["return !(a == b);".into()]),
+            ..Function::default()
+        }),
+    ));
     file.declarations.push(Declaration::Struct(Struct {
         name: name.into(),
         members,

tests/driver_lib/cbindgen.rs

@@ -160,6 +160,8 @@ fn gen_corelib(include_dir: &Path) -> anyhow::Result<()> {
             private_default_tagged_enum_constructor: true,
             ..Default::default()
         };
+        special_config.structure.derive_eq = true;
+        special_config.structure.derive_neq = true;
         // Put the rust type in a deeper "types" namespace, so the use of same type in for example generated
         // Property<> fields uses the public `sixtyfps::Blah` type
         special_config.namespaces =