Fix T51461: Outliner: Problems removing multiple collections in sequence

We now select the LayerCollection at index 0 for the active ViewLayer after a
collection deletion operation.

Added some functions to query outliner tree data & get LayerCollection
by index using a similar approach as we do for SceneCollection indexing.

With warning and style cleanups by Dalai Felinto.

Reviewers: dfelinto

Tags: #bf_blender_2.8

Differential Revision: https://developer.blender.org/D2942

source/blender/editors/space_outliner/outliner_collections.c

@@ -108,6 +108,46 @@ static SceneCollection *scene_collection_from_index(ListBase *lb, const int numb
 	return NULL;
 }
 
+typedef struct TreeElementFindData {
+	SceneCollection *sc;
+	TreeElement *te;
+} TreeElementFindData;
+
+static TreeTraversalAction tree_element_find_by_scene_collection(TreeElement *te, void *customdata)
+{
+	TreeElementFindData *data = customdata;
+
+	SceneCollection *current_element_sc = outliner_scene_collection_from_tree_element(te);
+
+	if (current_element_sc == data->sc) {
+		data->te = te;
+		return TRAVERSE_BREAK;
+	}
+
+	return TRAVERSE_CONTINUE;
+}
+
+static TreeElement *outliner_tree_element_from_layer_collection(bContext *C)
+{
+	ViewLayer *view_layer = CTX_data_view_layer(C);
+	SpaceOops *soops = CTX_wm_space_outliner(C);
+
+	LayerCollection *lc = BKE_layer_collection_from_index(view_layer, 0);
+
+	if (lc == NULL) {
+		return NULL;
+	}
+
+	/* Find the tree element containing the LayerCollection's scene_collection. */
+	TreeElementFindData data = {
+		.sc = lc->scene_collection,
+		.te = NULL,
+	};
+	outliner_tree_traverse(soops, &soops->tree, 0, 0, tree_element_find_by_scene_collection, &data);
+
+	return data.te;
+}
+
 static int collection_link_exec(bContext *C, wmOperator *op)
 {
 	Scene *scene = CTX_data_scene(C);
@@ -359,7 +399,9 @@ static TreeTraversalAction collection_find_data_to_delete(TreeElement *te, void
 
 static int collection_delete_exec(bContext *C, wmOperator *UNUSED(op))
 {
+	Main *bmain = CTX_data_main(C);
 	Scene *scene = CTX_data_scene(C);
+	ViewLayer *view_layer = CTX_data_view_layer(C);
 	SpaceOops *soops = CTX_wm_space_outliner(C);
 	struct CollectionDeleteData data = {.scene = scene, .soops = soops};
 
@@ -380,6 +422,15 @@ static int collection_delete_exec(bContext *C, wmOperator *UNUSED(op))
 
 	BLI_gset_free(data.collections_to_delete, NULL);
 
+	/* Rebuild the outliner tree before we select the tree element */
+	outliner_build_tree(bmain, scene, view_layer, soops);
+
+	TreeElement *select_te = outliner_tree_element_from_layer_collection(C);
+
+	if (select_te) {
+		outliner_item_select(soops, select_te, false, false);
+	}
+
 	DEG_relations_tag_update(CTX_data_main(C));
 
 	/* TODO(sergey): Use proper flag for tagging here. */

source/blender/editors/space_outliner/outliner_intern.h

@@ -203,6 +203,10 @@ int outliner_item_do_activate_from_cursor(
         struct bContext *C, const int mval[2],
         bool extend, bool recursive);
 
+void outliner_item_select(
+        struct SpaceOops *soops, const struct TreeElement *te,
+        const bool extend, const bool toggle);
+
 /* outliner_edit.c ---------------------------------------------- */
 typedef void (*outliner_operation_cb)(
         struct bContext *C, struct ReportList *, struct Scene *scene,

source/blender/editors/space_outliner/outliner_select.c

@@ -973,7 +973,7 @@ static void do_outliner_item_activate_tree_element(
  * \param extend: Don't deselect other items, only modify \a te.
  * \param toggle: Select \a te when not selected, deselect when selected.
  */
-static void outliner_item_select(SpaceOops *soops, const TreeElement *te, const bool extend, const bool toggle)
+void outliner_item_select(SpaceOops *soops, const TreeElement *te, const bool extend, const bool toggle)
 {
 	TreeStoreElem *tselem = TREESTORE(te);
 	const short new_flag = toggle ? (tselem->flag ^ TSE_SELECTED) : (tselem->flag | TSE_SELECTED);