Depsgraph: Keep track of original particle system

Allows to have quicker lookup in particle edit mode.

source/blender/blenkernel/BKE_particle.h

@@ -302,6 +302,7 @@ void psys_set_current_num(Object *ob, int index);
 
 struct LatticeDeformData *psys_create_lattice_deform_data(struct ParticleSimulationData *sim);
 
+struct ParticleSystem *psys_original_get(struct ParticleSystem *psys);
 bool psys_in_edit_mode(struct Depsgraph *depsgraph, struct ParticleSystem *psys);
 bool psys_check_enabled(struct Object *ob, struct ParticleSystem *psys, const bool use_render_params);
 bool psys_check_edited(struct ParticleSystem *psys);

source/blender/blenkernel/intern/particle.c

@@ -289,6 +289,14 @@ void psys_enable_all(Object *ob)
 		psys->flag &= ~PSYS_DISABLED;
 }
 
+ParticleSystem *psys_original_get(ParticleSystem *psys)
+{
+	if (psys->orig_psys == NULL) {
+		return psys;
+	}
+	return psys->orig_psys;
+}
+
 bool psys_in_edit_mode(Depsgraph *depsgraph, ParticleSystem *psys)
 {
 	const ViewLayer *view_layer = DEG_get_input_view_layer(depsgraph);
@@ -301,19 +309,7 @@ bool psys_in_edit_mode(Depsgraph *depsgraph, ParticleSystem *psys)
 	if (object->mode != OB_MODE_PARTICLE_EDIT) {
 		return false;
 	}
-	/* TODO(sergey): Find a faster way to switch to an original psys. */
-	/*const*/ Object *object_orig = DEG_get_original_object(view_layer->basact->object);
-	ParticleSystem *psys_orig = object_orig->particlesystem.first;
-	while (psys_orig != NULL) {
-		if (STREQ(psys_orig->name, psys->name)) {
-			break;
-		}
-		psys = psys->next;
-		psys_orig = psys_orig->next;
-	}
-	if (psys_orig != psys_get_current(object_orig)) {
-		return false;
-	}
+	ParticleSystem *psys_orig = psys_original_get(psys);
 	return (psys_orig->edit || psys->pointcache->edit) &&
 	       (use_render_params == false);
 }

source/blender/blenloader/intern/readfile.c

@@ -4476,6 +4476,7 @@ static void direct_link_particlesystems(FileData *fd, ListBase *particles)
 		psys->tree = NULL;
 		psys->bvhtree = NULL;
 
+		psys->orig_psys = NULL;
 		psys->batch_cache = NULL;
 	}
 	return;

source/blender/depsgraph/intern/eval/deg_eval_copy_on_write.cc

@@ -67,6 +67,7 @@ extern "C" {
 #include "DNA_mesh_types.h"
 #include "DNA_scene_types.h"
 #include "DNA_object_types.h"
+#include "DNA_particle_types.h"
 
 #ifdef NESTED_ID_NASTY_WORKAROUND
 #  include "DNA_curve_types.h"
@@ -443,11 +444,26 @@ void updata_edit_mode_pointers(const Depsgraph *depsgraph,
 			break;
 		case ID_ME:
 			updata_mesh_edit_mode_pointers(depsgraph, id_orig, id_cow);
+			break;
 		default:
 			break;
 	}
 }
 
+void update_particle_system_orig_pointers(const Object *object_orig,
+                                          Object *object_cow)
+{
+	ParticleSystem *psys_cow =
+	        (ParticleSystem *) object_cow->particlesystem.first;
+	ParticleSystem *psys_orig =
+	        (ParticleSystem *) object_orig->particlesystem.first;
+	while (psys_orig != NULL) {
+		psys_cow->orig_psys = psys_orig;
+		psys_cow = psys_cow->next;
+		psys_orig = psys_orig->next;
+	}
+}
+
 /* Do some special treatment of data transfer from original ID to it's
  * CoW complementary part.
  *
@@ -473,6 +489,7 @@ void update_special_pointers(const Depsgraph *depsgraph,
 				BKE_pose_remap_bone_pointers((bArmature *)object_cow->data,
 				                             object_cow->pose);
 			}
+			update_particle_system_orig_pointers(object_orig, object_cow);
 			break;
 		}
 		default:

source/blender/draw/modes/particle_mode.c

@@ -183,6 +183,9 @@ static void particle_cache_populate(void *vedata, Object *object)
 	Object *object_orig = DEG_get_original_object(object);
 	PTCacheEdit *edit = PE_create_current(
 	        draw_ctx->depsgraph, scene_orig, object_orig);
+	/* NOTE: We need to pass evaluated particle system, which we need
+	 * to find first.
+	 */
 	ParticleSystem *psys = object->particlesystem.first;
 	ParticleSystem *psys_orig = object_orig->particlesystem.first;
 	while (psys_orig != NULL) {

source/blender/makesdna/DNA_particle_types.h

@@ -326,6 +326,15 @@ typedef struct ParticleSystem {
 	float lattice_strength;					/* influence of the lattice modifier */
 
 	void *batch_cache;
+
+	/* Set by dependency graph's copy-on-write, allows to quickly go
+	 * from evaluated particle system to original one.
+	 *
+	 * Original system will have this set to NULL.
+	 *
+	 * Use psys_original_get() function to access,
+	 */
+	struct ParticleSystem *orig_psys;
 } ParticleSystem;
 
 typedef enum eParticleDrawFlag {