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, 3 insertions, 3 deletions

diff --git a/scene/3d/spatial_velocity_tracker.cpp b/scene/3d/spatial_velocity_tracker.cpp
index c547e76e30..d96b003a81 100644
--- a/scene/3d/spatial_velocity_tracker.cpp
+++ b/scene/3d/spatial_velocity_tracker.cpp
@@ -53,11 +53,11 @@ void SpatialVelocityTracker::update_position(const Vector3 &p_position) {
 	if (position_history_len == 0 || position_history[0].frame != ph.frame) { //in same frame, use latest
 		position_history_len = MIN(position_history.size(), position_history_len + 1);
 		for (int i = position_history_len - 1; i > 0; i--) {
-			position_history[i] = position_history[i - 1];
+			position_history.write[i] = position_history[i - 1];
 		}
 	}
 
-	position_history[0] = ph;
+	position_history.write[0] = ph;
 }
 Vector3 SpatialVelocityTracker::get_tracked_linear_velocity() const {
 
@@ -114,7 +114,7 @@ void SpatialVelocityTracker::reset(const Vector3 &p_new_pos) {
 		ph.frame = Engine::get_singleton()->get_idle_frame_ticks();
 	}
 
-	position_history[0] = ph;
+	position_history.write[0] = ph;
 	position_history_len = 1;
 }