Make all complex function arguments be passed by const& for non-callback functions

CHANGELOG.md

@@ -3,6 +3,7 @@
 ----
 
 - Scaffolding: Decorate public functions with `__declspec(dllexport)` under Windows and `__attribute__((visibility("default")))` on other platforms
+- Core: Make complex function arguments be passed by `const&` for non-callback functions
 
 #### v0.4.0+v0.25.0
 

bindgen/src/bindings/cpp/gen_cpp/filters/mod.rs

@@ -4,6 +4,7 @@ pub(crate) use uniffi_bindgen::backend::filters::*;
 use uniffi_bindgen::{
     backend::CodeType,
     interface::{Argument, AsType, FfiType, Literal, Type, Variant},
+    ComponentInterface,
 };
 
 use crate::bindings::cpp::gen_cpp::{
@@ -177,12 +178,35 @@ pub(crate) fn class_name(nm: &str) -> Result<String> {
     Ok(CppCodeOracle.class_name(nm))
 }
 
-pub(crate) fn parameter(arg: &Argument) -> Result<String> {
-    Ok(match arg.as_type() {
-        Type::Object { .. } | Type::CallbackInterface { .. } => {
-            format!("const {} &{}", arg.as_codetype().type_label(), arg.name())
-        }
-        t => format!("{} {}", type_name(&t)?, arg.name()),
+pub(crate) fn by_ref(ci: &ComponentInterface, arg: &Argument) -> bool {
+    match arg.as_type() {
+        Type::UInt8
+        | Type::Int8
+        | Type::UInt16
+        | Type::Int16
+        | Type::UInt32
+        | Type::Int32
+        | Type::UInt64
+        | Type::Int64
+        | Type::Float32
+        | Type::Float64
+        | Type::Boolean
+        | Type::Optional { .. } => false,
+        Type::Enum {
+            module_path: _,
+            name,
+        } => match ci.get_enum_definition(&name) {
+            Some(_enum) => _enum.is_flat(),
+            None => false,
+        },
+        _ => true,
+    }
+}
+
+pub(crate) fn parameter(arg: &Argument, ci: &ComponentInterface) -> Result<String> {
+    Ok(match by_ref(ci, arg) {
+        true => format!("const {} &{}", arg.as_codetype().type_label(), arg.name()),
+        false => format!("{} {}", arg.as_codetype().type_label(), arg.name()),
     })
 }
 

bindgen/src/bindings/cpp/templates/callback.hpp

@@ -9,7 +9,10 @@ struct {{ canonical_type_name }} {
     virtual
     {%- match method.return_type() %}
     {% when Some with (return_type) %} {{ return_type|type_name }} {% else %} void {% endmatch -%}
-    {{ method.name()|fn_name }}({% call macros::param_list(method) %}) = 0;
+    {{ method.name()|fn_name }}(
+    {%- for arg in method.arguments() %}
+        {{- arg.as_type().borrow()|type_name }} {{ arg.name() }}{% if !loop.last %}, {% endif -%}
+    {% endfor %}) = 0;
     {%- endfor %}
 
     virtual ~{{ canonical_type_name }}() = default;

bindgen/src/bindings/cpp/templates/callback_iface_tmpl.cpp

@@ -60,7 +60,7 @@ int {{ class_name }}::callback_stub(uint64_t handle, uint32_t method, uint8_t *a
             auto ret = {% endif -%}
             impl->{{ method.name() }}(
             {%- for arg in method.arguments() %}
-            arg{{ loop.index0 }}{%- if !loop.last %}, {% else %}{% endif %}
+            std::move(arg{{ loop.index0 }}){%- if !loop.last %}, {% else %}{% endif %}
             {%- endfor -%}
         );
         {%- match method.return_type() %}

bindgen/src/bindings/cpp/templates/macros.cpp

@@ -27,7 +27,7 @@
 
 {% macro param_list(func) %}
 {%- for arg in func.arguments() -%}
-{{ arg|parameter }}
+{{ arg|parameter(ci) }}
 {%- if !loop.last -%}, {% endif -%}
 {% endfor -%}
 {% endmacro %}