Reduce unnecessary COW on Vector by make writing explicit

This commit makes operator[] on Vector const and adds a write proxy to it.  From
now on writes to Vectors need to happen through the .write proxy. So for
instance:

Vector<int> vec;
vec.push_back(10);
std::cout << vec[0] << std::endl;
vec.write[0] = 20;

Failing to use the .write proxy will cause a compilation error.

In addition COWable datatypes can now embed a CowData pointer to their data.
This means that String, CharString, and VMap no longer use or derive from
Vector.

_ALWAYS_INLINE_ and _FORCE_INLINE_ are now equivalent for debug and non-debug
builds. This is a lot faster for Vector in the editor and while running tests.
The reason why this difference used to exist is because force-inlined methods
used to give a bad debugging experience. After extensive testing with modern
compilers this is no longer the case.

1 files changed, 1 insertions, 1 deletions

diff --git a/scene/3d/mesh_instance.cpp b/scene/3d/mesh_instance.cpp
index 722eadb9ca..e277cae5b7 100644
--- a/scene/3d/mesh_instance.cpp
+++ b/scene/3d/mesh_instance.cpp
@@ -257,7 +257,7 @@ void MeshInstance::set_surface_material(int p_surface, const Ref<Material> &p_ma
 
 	ERR_FAIL_INDEX(p_surface, materials.size());
 
-	materials[p_surface] = p_material;
+	materials.write[p_surface] = p_material;
 
 	if (materials[p_surface].is_valid())
 		VS::get_singleton()->instance_set_surface_material(get_instance(), p_surface, materials[p_surface]->get_rid());