Initialize changes from local diff.

@@ -404,3 +404,3 @@
   BKE_view_layer_synced_ensure(scene, view_layer);
   if (ob == nullptr || ob != BKE_view_layer_active_object_get(view_layer) ||
-      ob->matbits == nullptr) {
+      ob->matbits == nullptr)

@@ -1044,3 +1045,3 @@
   BKE_view_layer_synced_ensure(scene, view_layer);
   if (ob == nullptr || ob != BKE_view_layer_active_object_get(view_layer) ||
-      ob->matbits == nullptr) {
+      ob->matbits == nullptr)

@@ -1524,2 +1559,3 @@
                                                TreeElement *cursor,
-                                               bool selecting)
+                                               bool selecting,
+                                               bool recurse,

@@ -1584,2 +1640,3 @@
 
-  do_outliner_range_select_recursive(&space_outliner->tree, active, cursor, false);
+  Collection *in_collection = nullptr;
+  if (recurse) {

@@ -1653,3 +1722,3 @@
   }
   else {
-    /* The row may also contain children, if one is hovered we want this instead of current te. */
+    /* The row may also contain children, if one is hovered we want this instead of current te.

@@ -1572,0 +1591,4 @@
+      /* Only actually select the object if
+         1. We are not restricted to any collection, or
+         2. The object is in fact in the given collection. */
+      if (!in_collection || BKE_collection_has_object_recursive(

@@ -1719,0 +1810,4 @@
+       select recursively. */
+    if (!recurse && (extend || use_range) &&
+        outliner_item_is_co_over_icon(activate_te, view_mval[0]))
+      return OPERATOR_CANCELLED;

@@ -1720,1 +1816,3 @@
-      do_outliner_range_select(C, space_outliner, activate_te, extend);
+      do_outliner_range_select(C, space_outliner, activate_te, extend, recurse);
+      if (recurse)
+        do_outliner_select_recursive(&activate_te->subtree, /*selecting=*/true, in_collection);

@@ -1728,0 +1827,4 @@
+
+      /* If we're CTRL+double-clicking and the element is aleady selected, skip the activation
+         straight to deselection */
+      if (extend && recurse && activate_tselem->flag & TSE_SELECTED)

@@ -1571,30 +1571,83 @@ void outliner_item_select(bContext *C,
   }
 }
 
+/* A simple but apparently effective solution for recursive selections. */

@@ -1574,0 +1577,4 @@
+  LISTBASE_FOREACH (TreeElement *, te, lb) {
+    TreeStoreElem *tselem = TREESTORE(te);
+
+    /* The desired behavior is only to select collections and object hierarchies

@@ -1585,0 +1620,4 @@
+       is kinda gross but necessary for consistent behavior in the recursive case. Essentially
+       we need to be sure that the object belongs to the right collection before setting the
+       SELECTED flag. */
+    bool can_select = !recurse || (tselem->type == TSE_LAYER_COLLECTION ||

@@ -1598,0 +1642,4 @@
+    if (!(tselem->flag & TSE_CLOSED) || recurse) {
+      /* If this tree element is a collection, then it sets the precedent for inclusion
+         of its subobjects. */
+      Collection *in_collection2 = in_collection;

@@ -1721,0 +1779,4 @@
+       to prevent selecting across collection boundaries. (Object hierarchies might cross
+       collection boundaries, i.e., children may be in different collections from their
+       parents.) */
+    Collection *in_collection = nullptr;

@@ -1728,2 +1817,2 @@
-      const bool select = !extend || !(activate_tselem->flag & TSE_ACTIVE &&
-                                       activate_tselem->flag & TSE_SELECTED);
+      bool select = !extend ||
+                    !(activate_tselem->flag & TSE_ACTIVE && activate_tselem->flag & TSE_SELECTED);

@@ -1596,0 +1643,4 @@
+      if (tselem->type == TSE_LAYER_COLLECTION) {
+        child_collection = static_cast<LayerCollection *>(te->directdata)->collection;
+      }
+      selecting = do_outliner_range_select_recursive(

@@ -1765,10 +1875,11 @@ static int outliner_item_activate_invoke(bContext *C, wmOperator *op, const wmEv
   const bool extend = RNA_boolean_get(op->ptr, "extend");
   const bool use_range = RNA_boolean_get(op->ptr, "extend_range");
   const bool deselect_all = RNA_boolean_get(op->ptr, "deselect_all");
+  const bool recurse = RNA_boolean_get(op->ptr, "recurse");