Outliner: Support box select on click+drag

release/scripts/presets/keyconfig/keymap_data/blender_default.py

@@ -710,6 +710,11 @@ def km_outliner(params):
         ("outliner.item_activate", {"type": 'LEFTMOUSE', "value": 'CLICK', "shift": True, "ctrl": True},
          {"properties": [("extend", True), ("recursive", True)]}),
         ("outliner.select_box", {"type": 'B', "value": 'PRESS'}, None),
+        ("outliner.select_box", {"type": 'EVT_TWEAK_L', "value": 'ANY'}, {"properties": [("tweak", True)]}),
+        ("outliner.select_box", {"type": 'EVT_TWEAK_L', "value": 'ANY', "shift": True},
+         {"properties": [("tweak", True), ("mode", "ADD")]}),
+        ("outliner.select_box", {"type": 'EVT_TWEAK_L', "value": 'ANY', "ctrl": True},
+         {"properties": [("tweak", True), ("mode", "SUB")]}),
         ("outliner.select_walk", {"type": 'UP_ARROW', "value": 'PRESS'}, {"properties": [("direction", 'UP')]}),
         ("outliner.select_walk", {"type": 'UP_ARROW', "value": 'PRESS', "shift": True},
          {"properties": [("direction", 'UP'), ("extend", True)]}),

source/blender/editors/space_outliner/outliner_dragdrop.c

@@ -895,6 +895,12 @@ static int outliner_item_drag_drop_invoke(bContext *C,
     return (OPERATOR_CANCELLED | OPERATOR_PASS_THROUGH);
   }
 
+  float view_mval[2];
+  UI_view2d_region_to_view(&ar->v2d, event->mval[0], event->mval[1], &view_mval[0], &view_mval[1]);
+  if (outliner_item_is_co_within_close_toggle(te, view_mval[0])) {
+    return (OPERATOR_CANCELLED | OPERATOR_PASS_THROUGH);
+  }
+
   wmDrag *drag = WM_event_start_drag(C, data.icon, WM_DRAG_ID, NULL, 0.0, WM_DRAG_NOP);
 
   if (ELEM(GS(data.drag_id->name), ID_OB, ID_GR)) {

source/blender/editors/space_outliner/outliner_select.c

@@ -1428,6 +1428,37 @@ static int outliner_box_select_exec(bContext *C, wmOperator *op)
   return OPERATOR_FINISHED;
 }
 
+/* Find if x coordinate is over an icon or name */
+static bool outliner_item_is_co_over_name_icons(TreeElement *te, float view_co_x)
+{
+  /* Special case: count area left of Scene Collection as empty space */
+  bool outside_left = (TREESTORE(te)->type == TSE_VIEW_COLLECTION_BASE) ?
+                          (view_co_x > te->xs + UI_UNIT_X) :
+                          (view_co_x > te->xs);
+
+  return outside_left && (view_co_x < te->xend);
+}
+
+static int outliner_box_select_invoke(bContext *C, wmOperator *op, const wmEvent *event)
+{
+  SpaceOutliner *soops = CTX_wm_space_outliner(C);
+  ARegion *ar = CTX_wm_region(C);
+  float view_mval[2];
+  const bool tweak = RNA_boolean_get(op->ptr, "tweak");
+
+  UI_view2d_region_to_view(&ar->v2d, event->mval[0], event->mval[1], &view_mval[0], &view_mval[1]);
+
+  /* Find element clicked on */
+  TreeElement *te = outliner_find_item_at_y(soops, &soops->tree, view_mval[1]);
+
+  /* Pass through if click is over name or icons, or not tweak event */
+  if (te && tweak && outliner_item_is_co_over_name_icons(te, view_mval[0])) {
+    return OPERATOR_CANCELLED | OPERATOR_PASS_THROUGH;
+  }
+
+  return WM_gesture_box_invoke(C, op, event);
+}
+
 void OUTLINER_OT_select_box(wmOperatorType *ot)
 {
   /* identifiers */
@@ -1436,7 +1467,7 @@ void OUTLINER_OT_select_box(wmOperatorType *ot)
   ot->description = "Use box selection to select tree elements";
 
   /* api callbacks */
-  ot->invoke = WM_gesture_box_invoke;
+  ot->invoke = outliner_box_select_invoke;
   ot->exec = outliner_box_select_exec;
   ot->modal = WM_gesture_box_modal;
   ot->cancel = WM_gesture_box_cancel;
@@ -1447,6 +1478,12 @@ void OUTLINER_OT_select_box(wmOperatorType *ot)
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 
   /* properties */
+  PropertyRNA *prop;
+
+  prop = RNA_def_boolean(
+      ot->srna, "tweak", false, "Tweak", "Tweak gesture from empty space for box selection");
+  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
+
   WM_operator_properties_gesture_box(ot);
   WM_operator_properties_select_operation_simple(ot);
 }