-Fixes to undo redo to avoid crash, closes #24251

-Changed Animation to have a special signal when tracks are changed, to avoid unnecesary track cache rebuilds in AnimationPlayer
-Added missing emit_changed whe modifying keys to Animation
-Changed AnimationPlayer to use the new refcounted connections instead of the previous hacky way to keep references
-Changed AnimationEditor to update the current track when keys are edited
-Fixed bug where undo/redo did not work with AnimationKeyEdit (was not being updated)
-Made sure UndoRedo does not mind deleted objects in undo/redo history, this would corrupt the history or clear it without need.

5 files changed, 21 insertions, 17 deletions

diff --git a/scene/animation/animation_player.cpp b/scene/animation/animation_player.cpp
index 54be2aa159..86fd1ef14c 100644
--- a/scene/animation/animation_player.cpp
+++ b/scene/animation/animation_player.cpp
@@ -991,25 +991,12 @@ void AnimationPlayer::remove_animation(const StringName &p_name) {
 
 void AnimationPlayer::_ref_anim(const Ref<Animation> &p_anim) {
 
-	if (used_anims.has(p_anim))
-		used_anims[p_anim]++;
-	else {
-		used_anims[p_anim] = 1;
-		Ref<Animation>(p_anim)->connect("changed", this, "_animation_changed");
-	}
+	Ref<Animation>(p_anim)->connect(SceneStringNames::get_singleton()->tracks_changed, this, "_animation_changed", varray(), CONNECT_REFERENCE_COUNTED);
 }
 
 void AnimationPlayer::_unref_anim(const Ref<Animation> &p_anim) {
 
-	ERR_FAIL_COND(!used_anims.has(p_anim));
-
-	int &n = used_anims[p_anim];
-	n--;
-	if (n == 0) {
-
-		Ref<Animation>(p_anim)->disconnect("changed", this, "_animation_changed");
-		used_anims.erase(p_anim);
-	}
+	Ref<Animation>(p_anim)->disconnect(SceneStringNames::get_singleton()->tracks_changed, this, "_animation_changed");
 }
 
 void AnimationPlayer::rename_animation(const StringName &p_name, const StringName &p_new_name) {
diff --git a/scene/animation/animation_player.h b/scene/animation/animation_player.h
index 9bba848298..fea4819821 100644
--- a/scene/animation/animation_player.h
+++ b/scene/animation/animation_player.h
@@ -181,8 +181,6 @@ private:
 	int cache_update_bezier_size;
 	Set<TrackNodeCache *> playing_caches;
 
-	Map<Ref<Animation>, int> used_anims;
-
 	uint64_t accum_pass;
 	float speed_scale;
 	float default_blend_time;
diff --git a/scene/resources/animation.cpp b/scene/resources/animation.cpp
index 3156e12c50..a7544cc031 100644
--- a/scene/resources/animation.cpp
+++ b/scene/resources/animation.cpp
@@ -29,6 +29,7 @@
 /*************************************************************************/
 
 #include "animation.h"
+#include "scene/scene_string_names.h"
 
 #include "core/math/geometry.h"
 
@@ -668,6 +669,7 @@ int Animation::add_track(TrackType p_type, int p_at_pos) {
 		}
 	}
 	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 	return p_at_pos;
 }
 
@@ -719,6 +721,7 @@ void Animation::remove_track(int p_track) {
 	memdelete(t);
 	tracks.remove(p_track);
 	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 }
 
 int Animation::get_track_count() const {
@@ -737,6 +740,7 @@ void Animation::track_set_path(int p_track, const NodePath &p_path) {
 	ERR_FAIL_INDEX(p_track, tracks.size());
 	tracks[p_track]->path = p_path;
 	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 }
 
 NodePath Animation::track_get_path(int p_track) const {
@@ -1410,6 +1414,8 @@ void Animation::track_set_key_value(int p_track, int p_key_idx, const Variant &p
 
 		} break;
 	}
+
+	emit_changed();
 }
 
 void Animation::track_set_key_transition(int p_track, int p_key_idx, float p_transition) {
@@ -1445,6 +1451,8 @@ void Animation::track_set_key_transition(int p_track, int p_key_idx, float p_tra
 			// they don't use transition
 		} break;
 	}
+
+	emit_changed();
 }
 
 template <class K>
@@ -2554,6 +2562,7 @@ void Animation::track_move_up(int p_track) {
 	}
 
 	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 }
 
 void Animation::track_set_imported(int p_track, bool p_imported) {
@@ -2588,6 +2597,7 @@ void Animation::track_move_down(int p_track) {
 		SWAP(tracks.write[p_track], tracks.write[p_track - 1]);
 	}
 	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 }
 
 void Animation::track_swap(int p_track, int p_with_track) {
@@ -2598,6 +2608,7 @@ void Animation::track_swap(int p_track, int p_with_track) {
 		return;
 	SWAP(tracks.write[p_track], tracks.write[p_with_track]);
 	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 }
 
 void Animation::set_step(float p_step) {
@@ -2716,6 +2727,8 @@ void Animation::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "loop"), "set_loop", "has_loop");
 	ADD_PROPERTY(PropertyInfo(Variant::REAL, "step", PROPERTY_HINT_RANGE, "0,4096,0.001"), "set_step", "get_step");
 
+	ADD_SIGNAL(MethodInfo("tracks_changed"));
+
 	BIND_ENUM_CONSTANT(TYPE_VALUE);
 	BIND_ENUM_CONSTANT(TYPE_TRANSFORM);
 	BIND_ENUM_CONSTANT(TYPE_METHOD);
@@ -2740,6 +2753,8 @@ void Animation::clear() {
 	tracks.clear();
 	loop = false;
 	length = 1;
+	emit_changed();
+	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
 }
 
 bool Animation::_transform_track_optimize_key(const TKey<TransformKey> &t0, const TKey<TransformKey> &t1, const TKey<TransformKey> &t2, float p_alowed_linear_err, float p_alowed_angular_err, float p_max_optimizable_angle, const Vector3 &p_norm) {
diff --git a/scene/scene_string_names.cpp b/scene/scene_string_names.cpp
index 305e4fc735..634f4d7160 100644
--- a/scene/scene_string_names.cpp
+++ b/scene/scene_string_names.cpp
@@ -203,4 +203,6 @@ SceneStringNames::SceneStringNames() {
 	_mesh_changed = StaticCString::create("_mesh_changed");
 
 	parameters_base_path = "parameters/";
+
+	tracks_changed = "tracks_changed";
 }
diff --git a/scene/scene_string_names.h b/scene/scene_string_names.h
index 4d1a7f255c..bc75165b8c 100644
--- a/scene/scene_string_names.h
+++ b/scene/scene_string_names.h
@@ -205,6 +205,8 @@ public:
 
 	StringName parameters_base_path;
 
+	StringName tracks_changed;
+
 	enum {
 		MAX_MATERIALS = 32
 	};