12 files changed, 224 insertions, 88 deletions
diff --git a/core/object.cpp b/core/object.cpp
index e83abaece7..24a31930a0 100644
--- a/core/object.cpp
+++ b/core/object.cpp
@@ -1916,7 +1916,11 @@ void *Object::get_script_instance_binding(int p_script_language_index) {
 	//as it should not really affect performance much (won't be called too often), as in far most caes the condition below will be false afterwards
 
 	if (!_script_instance_bindings[p_script_language_index]) {
-		_script_instance_bindings[p_script_language_index] = ScriptServer::get_language(p_script_language_index)->alloc_instance_binding_data(this);
+		void *script_data = ScriptServer::get_language(p_script_language_index)->alloc_instance_binding_data(this);
+		if (script_data) {
+			atomic_increment(&instance_binding_count);
+			_script_instance_bindings[p_script_language_index] = script_data;
+		}
 	}
 
 	return _script_instance_bindings[p_script_language_index];
@@ -1931,6 +1935,7 @@ Object::Object() {
 	_instance_ID = ObjectDB::add_instance(this);
 	_can_translate = true;
 	_is_queued_for_deletion = false;
+	instance_binding_count = 0;
 	memset(_script_instance_bindings, 0, sizeof(void *) * MAX_SCRIPT_INSTANCE_BINDINGS);
 	script_instance = NULL;
 #ifdef TOOLS_ENABLED
diff --git a/core/object.h b/core/object.h
index d741371306..43e1cf4785 100644
--- a/core/object.h
+++ b/core/object.h
@@ -490,10 +490,12 @@ private:
 	void _set_indexed_bind(const NodePath &p_name, const Variant &p_value);
 	Variant _get_indexed_bind(const NodePath &p_name) const;
 
-	void *_script_instance_bindings[MAX_SCRIPT_INSTANCE_BINDINGS];
-
 	void property_list_changed_notify();
 
+	friend class Reference;
+	uint32_t instance_binding_count;
+	void *_script_instance_bindings[MAX_SCRIPT_INSTANCE_BINDINGS];
+
 protected:
 	virtual void _initialize_classv() { initialize_class(); }
 	virtual bool _setv(const StringName &p_name, const Variant &p_property) { return false; };
diff --git a/core/reference.cpp b/core/reference.cpp
index c33a7c683c..6e1520d81d 100644
--- a/core/reference.cpp
+++ b/core/reference.cpp
@@ -66,8 +66,17 @@ int Reference::reference_get_count() const {
 bool Reference::reference() {
 	bool success = refcount.ref();
 
-	if (success && get_script_instance()) {
-		get_script_instance()->refcount_incremented();
+	if (success && refcount.get() <= 2 /* higher is not relevant */) {
+		if (get_script_instance()) {
+			get_script_instance()->refcount_incremented();
+		}
+		if (instance_binding_count > 0) {
+			for (int i = 0; i < MAX_SCRIPT_INSTANCE_BINDINGS; i++) {
+				if (_script_instance_bindings[i]) {
+					ScriptServer::get_language(i)->refcount_incremented_instance_binding(this);
+				}
+			}
+		}
 	}
 
 	return success;
@@ -77,9 +86,19 @@ bool Reference::unreference() {
 
 	bool die = refcount.unref();
 
-	if (get_script_instance()) {
-		bool script_ret = get_script_instance()->refcount_decremented();
-		die = die && script_ret;
+	if (refcount.get() <= 1 /* higher is not relevant */) {
+		if (get_script_instance()) {
+			bool script_ret = get_script_instance()->refcount_decremented();
+			die = die && script_ret;
+		}
+		if (instance_binding_count > 0) {
+			for (int i = 0; i < MAX_SCRIPT_INSTANCE_BINDINGS; i++) {
+				if (_script_instance_bindings[i]) {
+					bool script_ret = ScriptServer::get_language(i)->refcount_decremented_instance_binding(this);
+					die = die && script_ret;
+				}
+			}
+		}
 	}
 
 	return die;
diff --git a/core/script_language.h b/core/script_language.h
index 71b705e960..573e7b4fa1 100644
--- a/core/script_language.h
+++ b/core/script_language.h
@@ -311,6 +311,8 @@ public:
 
 	virtual void *alloc_instance_binding_data(Object *p_object) { return NULL; } //optional, not used by all languages
 	virtual void free_instance_binding_data(void *p_data) {} //optional, not used by all languages
+	virtual void refcount_incremented_instance_binding(Object *p_object) {} //optional, not used by all languages
+	virtual bool refcount_decremented_instance_binding(Object *p_object) { return true; } //return true if it can die //optional, not used by all languages
 
 	virtual void frame();
 
diff --git a/editor/plugins/texture_region_editor_plugin.cpp b/editor/plugins/texture_region_editor_plugin.cpp
index 4a9cbfe535..4390b94ece 100644
--- a/editor/plugins/texture_region_editor_plugin.cpp
+++ b/editor/plugins/texture_region_editor_plugin.cpp
@@ -356,8 +356,6 @@ void TextureRegionEditor::_region_input(const Ref<InputEvent> &p_input) {
 						undo_redo->add_do_method(atlas_tex.ptr(), "set_region", atlas_tex->get_region());
 						undo_redo->add_undo_method(atlas_tex.ptr(), "set_region", rect_prev);
 					} else if (node_ninepatch) {
-						// FIXME: Is this intentional?
-					} else if (node_ninepatch) {
 						undo_redo->add_do_method(node_ninepatch, "set_region_rect", node_ninepatch->get_region_rect());
 						undo_redo->add_undo_method(node_ninepatch, "set_region_rect", rect_prev);
 					} else if (obj_styleBox.is_valid()) {
@@ -521,6 +519,10 @@ void TextureRegionEditor::_set_snap_mode(int p_mode) {
 	else
 		hb_grid->hide();
 
+	if (snap_mode == SNAP_AUTOSLICE && is_visible() && autoslice_is_dirty) {
+		_update_autoslice();
+	}
+
 	edit_draw->update();
 }
 
@@ -562,7 +564,8 @@ void TextureRegionEditor::_zoom_in() {
 }
 
 void TextureRegionEditor::_zoom_reset() {
-	if (draw_zoom == 1) return;
+	if (draw_zoom == 1)
+		return;
 	draw_zoom = 1;
 	edit_draw->update();
 }
@@ -585,25 +588,91 @@ void TextureRegionEditor::apply_rect(const Rect2 &rect) {
 		atlas_tex->set_region(rect);
 }
 
-void TextureRegionEditor::_notification(int p_what) {
-	switch (p_what) {
-		case NOTIFICATION_PROCESS: {
-			if (node_sprite) {
-				if (node_sprite->is_region()) {
+void TextureRegionEditor::_update_autoslice() {
+	autoslice_is_dirty = false;
+	autoslice_cache.clear();
 
-					set_process(false);
-					EditorNode::get_singleton()->make_bottom_panel_item_visible(this);
+	Ref<Texture> texture = NULL;
+	if (node_sprite)
+		texture = node_sprite->get_texture();
+	else if (node_ninepatch)
+		texture = node_ninepatch->get_texture();
+	else if (obj_styleBox.is_valid())
+		texture = obj_styleBox->get_texture();
+	else if (atlas_tex.is_valid())
+		texture = atlas_tex->get_atlas();
+
+	if (texture.is_null()) {
+		return;
+	}
+
+	for (int y = 0; y < texture->get_height(); y++) {
+		for (int x = 0; x < texture->get_width(); x++) {
+			if (texture->is_pixel_opaque(x, y)) {
+				bool found = false;
+				for (List<Rect2>::Element *E = autoslice_cache.front(); E; E = E->next()) {
+					Rect2 grown = E->get().grow(1.5);
+					if (grown.has_point(Point2(x, y))) {
+						E->get().expand_to(Point2(x, y));
+						E->get().expand_to(Point2(x + 1, y + 1));
+						x = E->get().position.x + E->get().size.x - 1;
+						bool merged = true;
+						while (merged) {
+							merged = false;
+							bool queue_erase = false;
+							for (List<Rect2>::Element *F = autoslice_cache.front(); F; F = F->next()) {
+								if (queue_erase) {
+									autoslice_cache.erase(F->prev());
+									queue_erase = false;
+								}
+								if (F == E)
+									continue;
+								if (E->get().grow(1).intersects(F->get())) {
+									E->get().expand_to(F->get().position);
+									E->get().expand_to(F->get().position + F->get().size);
+									if (F->prev()) {
+										F = F->prev();
+										autoslice_cache.erase(F->next());
+									} else {
+										queue_erase = true;
+										// Can't delete the first rect in the list.
+									}
+									merged = true;
+								}
+							}
+						}
+						found = true;
+						break;
+					}
+				}
+				if (!found) {
+					Rect2 new_rect(x, y, 1, 1);
+					autoslice_cache.push_back(new_rect);
 				}
-			} else {
-				set_process(false);
 			}
-		} break;
-		case NOTIFICATION_THEME_CHANGED:
+		}
+	}
+	cache_map[texture->get_rid()] = autoslice_cache;
+}
+
+void TextureRegionEditor::_notification(int p_what) {
+	switch (p_what) {
 		case NOTIFICATION_READY: {
 			zoom_out->set_icon(get_icon("ZoomLess", "EditorIcons"));
 			zoom_reset->set_icon(get_icon("ZoomReset", "EditorIcons"));
 			zoom_in->set_icon(get_icon("ZoomMore", "EditorIcons"));
 		} break;
+		case NOTIFICATION_VISIBILITY_CHANGED: {
+			if (snap_mode == SNAP_AUTOSLICE && is_visible() && autoslice_is_dirty) {
+				_update_autoslice();
+			}
+		} break;
+		case MainLoop::NOTIFICATION_WM_FOCUS_IN: {
+			// This happens when the user leaves the Editor and returns,
+			// he/she could have changed the textures, so the cache is cleared
+			cache_map.clear();
+			_edit_region();
+		} break;
 	}
 }
 
@@ -709,57 +778,15 @@ void TextureRegionEditor::_edit_region() {
 		return;
 	}
 
-	autoslice_cache.clear();
-	Ref<Image> i;
-	i.instance();
-	if (i->load(texture->get_path()) == OK) {
-		BitMap bm;
-		bm.create_from_image_alpha(i);
-		for (int y = 0; y < i->get_height(); y++) {
-			for (int x = 0; x < i->get_width(); x++) {
-				if (bm.get_bit(Point2(x, y))) {
-					bool found = false;
-					for (List<Rect2>::Element *E = autoslice_cache.front(); E; E = E->next()) {
-						Rect2 grown = E->get().grow(1.5);
-						if (grown.has_point(Point2(x, y))) {
-							E->get().expand_to(Point2(x, y));
-							E->get().expand_to(Point2(x + 1, y + 1));
-							x = E->get().position.x + E->get().size.x - 1;
-							bool merged = true;
-							while (merged) {
-								merged = false;
-								bool queue_erase = false;
-								for (List<Rect2>::Element *F = autoslice_cache.front(); F; F = F->next()) {
-									if (queue_erase) {
-										autoslice_cache.erase(F->prev());
-										queue_erase = false;
-									}
-									if (F == E)
-										continue;
-									if (E->get().grow(1).intersects(F->get())) {
-										E->get().expand_to(F->get().position);
-										E->get().expand_to(F->get().position + F->get().size);
-										if (F->prev()) {
-											F = F->prev();
-											autoslice_cache.erase(F->next());
-										} else {
-											queue_erase = true;
-											//Can't delete the first rect in the list.
-										}
-										merged = true;
-									}
-								}
-							}
-							found = true;
-							break;
-						}
-					}
-					if (!found) {
-						Rect2 new_rect(x, y, 1, 1);
-						autoslice_cache.push_back(new_rect);
-					}
-				}
-			}
+	if (cache_map.has(texture->get_rid())) {
+		autoslice_cache = cache_map[texture->get_rid()];
+		autoslice_is_dirty = false;
+		return;
+	} else {
+		if (is_visible() && snap_mode == SNAP_AUTOSLICE) {
+			_update_autoslice();
+		} else {
+			autoslice_is_dirty = true;
 		}
 	}
 
diff --git a/editor/plugins/texture_region_editor_plugin.h b/editor/plugins/texture_region_editor_plugin.h
index 670cc86bbb..61ef769f89 100644
--- a/editor/plugins/texture_region_editor_plugin.h
+++ b/editor/plugins/texture_region_editor_plugin.h
@@ -92,7 +92,9 @@ class TextureRegionEditor : public Control {
 	Rect2 rect_prev;
 	float prev_margin;
 	int edited_margin;
+	Map<RID, List<Rect2> > cache_map;
 	List<Rect2> autoslice_cache;
+	bool autoslice_is_dirty;
 
 	bool drag;
 	bool creating;
@@ -110,6 +112,7 @@ class TextureRegionEditor : public Control {
 	void _zoom_reset();
 	void _zoom_out();
 	void apply_rect(const Rect2 &rect);
+	void _update_autoslice();
 
 protected:
 	void _notification(int p_what);
diff --git a/modules/mono/csharp_script.cpp b/modules/mono/csharp_script.cpp
index b8b77924f7..d2a861dbe8 100644
--- a/modules/mono/csharp_script.cpp
+++ b/modules/mono/csharp_script.cpp
@@ -1013,6 +1013,69 @@ void CSharpLanguage::free_instance_binding_data(void *p_data) {
 #endif
 }
 
+void CSharpLanguage::refcount_incremented_instance_binding(Object *p_object) {
+
+	Reference *ref_owner = Object::cast_to<Reference>(p_object);
+
+#ifdef DEBUG_ENABLED
+	CRASH_COND(!ref_owner);
+#endif
+
+	void *data = p_object->get_script_instance_binding(get_language_index());
+	if (!data)
+		return;
+	Ref<MonoGCHandle> &gchandle = ((Map<Object *, Ref<MonoGCHandle> >::Element *)data)->get();
+
+	if (ref_owner->reference_get_count() > 1 && gchandle->is_weak()) { // The managed side also holds a reference, hence 1 instead of 0
+		// The reference count was increased after the managed side was the only one referencing our owner.
+		// This means the owner is being referenced again by the unmanaged side,
+		// so the owner must hold the managed side alive again to avoid it from being GCed.
+
+		MonoObject *target = gchandle->get_target();
+		if (!target)
+			return; // Called after the managed side was collected, so nothing to do here
+
+		// Release the current weak handle and replace it with a strong handle.
+		uint32_t strong_gchandle = MonoGCHandle::make_strong_handle(target);
+		gchandle->release();
+		gchandle->set_handle(strong_gchandle, MonoGCHandle::STRONG_HANDLE);
+	}
+}
+
+bool CSharpLanguage::refcount_decremented_instance_binding(Object *p_object) {
+
+	Reference *ref_owner = Object::cast_to<Reference>(p_object);
+
+#ifdef DEBUG_ENABLED
+	CRASH_COND(!ref_owner);
+#endif
+
+	int refcount = ref_owner->reference_get_count();
+
+	void *data = p_object->get_script_instance_binding(get_language_index());
+	if (!data)
+		return refcount == 0;
+	Ref<MonoGCHandle> &gchandle = ((Map<Object *, Ref<MonoGCHandle> >::Element *)data)->get();
+
+	if (refcount == 1 && !gchandle->is_weak()) { // The managed side also holds a reference, hence 1 instead of 0
+		// If owner owner is no longer referenced by the unmanaged side,
+		// the managed instance takes responsibility of deleting the owner when GCed.
+
+		MonoObject *target = gchandle->get_target();
+		if (!target)
+			return refcount == 0; // Called after the managed side was collected, so nothing to do here
+
+		// Release the current strong handle and replace it with a weak handle.
+		uint32_t weak_gchandle = MonoGCHandle::make_weak_handle(target);
+		gchandle->release();
+		gchandle->set_handle(weak_gchandle, MonoGCHandle::WEAK_HANDLE);
+
+		return false;
+	}
+
+	return refcount == 0;
+}
+
 CSharpInstance *CSharpInstance::create_for_managed_type(Object *p_owner, CSharpScript *p_script, const Ref<MonoGCHandle> &p_gchandle) {
 
 	CSharpInstance *instance = memnew(CSharpInstance);
@@ -1303,11 +1366,13 @@ void CSharpInstance::mono_object_disposed() {
 
 void CSharpInstance::refcount_incremented() {
 
+#ifdef DEBUG_ENABLED
 	CRASH_COND(!base_ref);
+#endif
 
 	Reference *ref_owner = Object::cast_to<Reference>(owner);
 
-	if (ref_owner->reference_get_count() > 1) { // The managed side also holds a reference, hence 1 instead of 0
+	if (ref_owner->reference_get_count() > 1 && gchandle->is_weak()) { // The managed side also holds a reference, hence 1 instead of 0
 		// The reference count was increased after the managed side was the only one referencing our owner.
 		// This means the owner is being referenced again by the unmanaged side,
 		// so the owner must hold the managed side alive again to avoid it from being GCed.
@@ -1315,26 +1380,28 @@ void CSharpInstance::refcount_incremented() {
 		// Release the current weak handle and replace it with a strong handle.
 		uint32_t strong_gchandle = MonoGCHandle::make_strong_handle(gchandle->get_target());
 		gchandle->release();
-		gchandle->set_handle(strong_gchandle);
+		gchandle->set_handle(strong_gchandle, MonoGCHandle::STRONG_HANDLE);
 	}
 }
 
 bool CSharpInstance::refcount_decremented() {
 
+#ifdef DEBUG_ENABLED
 	CRASH_COND(!base_ref);
+#endif
 
 	Reference *ref_owner = Object::cast_to<Reference>(owner);
 
 	int refcount = ref_owner->reference_get_count();
 
-	if (refcount == 1) { // The managed side also holds a reference, hence 1 instead of 0
+	if (refcount == 1 && !gchandle->is_weak()) { // The managed side also holds a reference, hence 1 instead of 0
 		// If owner owner is no longer referenced by the unmanaged side,
 		// the managed instance takes responsibility of deleting the owner when GCed.
 
 		// Release the current strong handle and replace it with a weak handle.
 		uint32_t weak_gchandle = MonoGCHandle::make_weak_handle(gchandle->get_target());
 		gchandle->release();
-		gchandle->set_handle(weak_gchandle);
+		gchandle->set_handle(weak_gchandle, MonoGCHandle::WEAK_HANDLE);
 
 		return false;
 	}
diff --git a/modules/mono/csharp_script.h b/modules/mono/csharp_script.h
index 53644eafae..1a5d0c8a69 100644
--- a/modules/mono/csharp_script.h
+++ b/modules/mono/csharp_script.h
@@ -346,6 +346,8 @@ public:
 	// Don't use these. I'm watching you
 	virtual void *alloc_instance_binding_data(Object *p_object);
 	virtual void free_instance_binding_data(void *p_data);
+	virtual void refcount_incremented_instance_binding(Object *p_object);
+	virtual bool refcount_decremented_instance_binding(Object *p_object);
 
 #ifdef DEBUG_ENABLED
 	Vector<StackInfo> stack_trace_get_info(MonoObject *p_stack_trace);
diff --git a/modules/mono/mono_gc_handle.cpp b/modules/mono/mono_gc_handle.cpp
index 12109045e0..9f0e933a8c 100644
--- a/modules/mono/mono_gc_handle.cpp
+++ b/modules/mono/mono_gc_handle.cpp
@@ -44,12 +44,12 @@ uint32_t MonoGCHandle::make_weak_handle(MonoObject *p_object) {
 
 Ref<MonoGCHandle> MonoGCHandle::create_strong(MonoObject *p_object) {
 
-	return memnew(MonoGCHandle(make_strong_handle(p_object)));
+	return memnew(MonoGCHandle(make_strong_handle(p_object), STRONG_HANDLE));
 }
 
 Ref<MonoGCHandle> MonoGCHandle::create_weak(MonoObject *p_object) {
 
-	return memnew(MonoGCHandle(make_weak_handle(p_object)));
+	return memnew(MonoGCHandle(make_weak_handle(p_object), WEAK_HANDLE));
 }
 
 void MonoGCHandle::release() {
@@ -64,9 +64,10 @@ void MonoGCHandle::release() {
 	}
 }
 
-MonoGCHandle::MonoGCHandle(uint32_t p_handle) {
+MonoGCHandle::MonoGCHandle(uint32_t p_handle, HandleType p_handle_type) {
 
 	released = false;
+	weak = p_handle_type == WEAK_HANDLE;
 	handle = p_handle;
 }
 
diff --git a/modules/mono/mono_gc_handle.h b/modules/mono/mono_gc_handle.h
index 9cb3ef0fbb..7eeaba30e0 100644
--- a/modules/mono/mono_gc_handle.h
+++ b/modules/mono/mono_gc_handle.h
@@ -40,24 +40,33 @@ class MonoGCHandle : public Reference {
 	GDCLASS(MonoGCHandle, Reference)
 
 	bool released;
+	bool weak;
 	uint32_t handle;
 
 public:
+	enum HandleType {
+		STRONG_HANDLE,
+		WEAK_HANDLE
+	};
+
 	static uint32_t make_strong_handle(MonoObject *p_object);
 	static uint32_t make_weak_handle(MonoObject *p_object);
 
 	static Ref<MonoGCHandle> create_strong(MonoObject *p_object);
 	static Ref<MonoGCHandle> create_weak(MonoObject *p_object);
 
+	_FORCE_INLINE_ bool is_weak() { return weak; }
+
 	_FORCE_INLINE_ MonoObject *get_target() const { return released ? NULL : mono_gchandle_get_target(handle); }
 
-	_FORCE_INLINE_ void set_handle(uint32_t p_handle) {
-		handle = p_handle;
+	_FORCE_INLINE_ void set_handle(uint32_t p_handle, HandleType p_handle_type) {
 		released = false;
+		weak = p_handle_type == WEAK_HANDLE;
+		handle = p_handle;
 	}
 	void release();
 
-	MonoGCHandle(uint32_t p_handle);
+	MonoGCHandle(uint32_t p_handle, HandleType p_handle_type);
 	~MonoGCHandle();
 };
 
diff --git a/modules/mono/signal_awaiter_utils.cpp b/modules/mono/signal_awaiter_utils.cpp
index 54720652fa..add1e506ea 100644
--- a/modules/mono/signal_awaiter_utils.cpp
+++ b/modules/mono/signal_awaiter_utils.cpp
@@ -42,8 +42,7 @@ Error connect_signal_awaiter(Object *p_source, const String &p_signal, Object *p
 	ERR_FAIL_NULL_V(p_source, ERR_INVALID_DATA);
 	ERR_FAIL_NULL_V(p_target, ERR_INVALID_DATA);
 
-	uint32_t awaiter_handle = MonoGCHandle::make_strong_handle(p_awaiter);
-	Ref<SignalAwaiterHandle> sa_con = memnew(SignalAwaiterHandle(awaiter_handle));
+	Ref<SignalAwaiterHandle> sa_con = memnew(SignalAwaiterHandle(p_awaiter));
 #ifdef DEBUG_ENABLED
 	sa_con->set_connection_target(p_target);
 #endif
@@ -119,8 +118,8 @@ void SignalAwaiterHandle::_bind_methods() {
 	ClassDB::bind_vararg_method(METHOD_FLAGS_DEFAULT, "_signal_callback", &SignalAwaiterHandle::_signal_callback, MethodInfo("_signal_callback"));
 }
 
-SignalAwaiterHandle::SignalAwaiterHandle(uint32_t p_managed_handle) :
-		MonoGCHandle(p_managed_handle) {
+SignalAwaiterHandle::SignalAwaiterHandle(MonoObject *p_managed) :
+		MonoGCHandle(MonoGCHandle::make_strong_handle(p_managed), STRONG_HANDLE) {
 
 #ifdef DEBUG_ENABLED
 	conn_target_id = 0;
diff --git a/modules/mono/signal_awaiter_utils.h b/modules/mono/signal_awaiter_utils.h
index a6a205ff8d..1920432709 100644
--- a/modules/mono/signal_awaiter_utils.h
+++ b/modules/mono/signal_awaiter_utils.h
@@ -64,7 +64,7 @@ public:
 	}
 #endif
 
-	SignalAwaiterHandle(uint32_t p_managed_handle);
+	SignalAwaiterHandle(MonoObject *p_managed);
 	~SignalAwaiterHandle();
 };