UI: Add context menu support for tree-view items

Tree-view items can now easily define their own context menu. This works
by overriding the `ui::AbstractTreeViewItem::build_context_menu()`
function. See the documentation:
https://wiki.blender.org/wiki/Source/Interface/Views#Context_Menus

Consistently with the Outliner and File Browser, the right-clicked item
also gets activated. This makes sure the correct context is set for the
operators and makes it clear to the user which item is operated on.

An operator to rename the active item is also added, which is something
you'd typically want to put in the context menu as well.

1 files changed, 8 insertions, 0 deletions

diff --git a/source/blender/editors/interface/interface_handlers.c b/source/blender/editors/interface/interface_handlers.c
index bf9b37c00fa..e1f8d18ce35 100644
--- a/source/blender/editors/interface/interface_handlers.c
+++ b/source/blender/editors/interface/interface_handlers.c
@@ -7961,6 +7961,14 @@ static int ui_do_button(bContext *C, uiBlock *block, uiBut *but, const wmEvent *
     /* handle menu */
     if ((event->type == RIGHTMOUSE) && !IS_EVENT_MOD(event, shift, ctrl, alt, oskey) &&
         (event->val == KM_PRESS)) {
+      /* For some button types that are typically representing entire sets of data, right-clicking
+       * to spawn the context menu should also activate the item. This makes it clear which item
+       * will be operated on.
+       * Apply the button immediately, so context menu polls get the right active item. */
+      if (ELEM(but->type, UI_BTYPE_TREEROW)) {
+        ui_apply_but(C, but->block, but, but->active, true);
+      }
+
       /* RMB has two options now */
       if (ui_popup_context_menu_for_button(C, but, event)) {
         return WM_UI_HANDLER_BREAK;