UI: Add AbstractView base class for views, unify reconstruction in there

No user visible changes expected.

There's plenty of duplicated code in the grid and the tree view, and I expect
this to become more. This starts the process of unifying these parts, which
should also make it easier to add new views. Complexity in the view classes is
reduced, and some type shenanigans for C compatibility and general view
management can be removed, since there is now a common base type.

For the start this ports some of the view reconstruction, where the view and
its items are compared to the version of itself in the previous redraw, so that
state (highlighted, active, renaming, collapsed, ...) can be preserved.
Notifier listening is also ported.

1 files changed, 3 insertions, 17 deletions

diff --git a/source/blender/editors/include/UI_grid_view.hh b/source/blender/editors/include/UI_grid_view.hh
index 6f553f4fad1..cabc49e411c 100644
--- a/source/blender/editors/include/UI_grid_view.hh
+++ b/source/blender/editors/include/UI_grid_view.hh
@@ -13,6 +13,7 @@
 #include "BLI_map.hh"
 #include "BLI_vector.hh"
 
+#include "UI_abstract_view.hh"
 #include "UI_resources.h"
 
 struct bContext;
@@ -111,7 +112,7 @@ struct GridViewStyle {
   int tile_height = 0;
 };
 
-class AbstractGridView {
+class AbstractGridView : public AbstractView {
   friend class AbstractGridViewItem;
   friend class GridViewBuilder;
   friend class GridViewLayoutBuilder;
@@ -122,7 +123,6 @@ class AbstractGridView {
    * #update_from_old(). */
   Map<StringRef, AbstractGridViewItem *> item_map_;
   GridViewStyle style_;
-  bool is_reconstructed_ = false;
 
  public:
   AbstractGridView();
@@ -131,9 +131,6 @@ class AbstractGridView {
   using ItemIterFn = FunctionRef<void(AbstractGridViewItem &)>;
   void foreach_item(ItemIterFn iter_fn) const;
 
-  /** Listen to a notifier, returning true if a redraw is needed. */
-  virtual bool listen(const wmNotifier &) const;
-
   /**
    * Convenience wrapper constructing the item by forwarding given arguments to the constructor of
    * the type (\a ItemT).
@@ -154,19 +151,8 @@ class AbstractGridView {
  protected:
   virtual void build_items() = 0;
 
-  /**
-   * Check if the view is fully (re-)constructed. That means, both #build_items() and
-   * #update_from_old() have finished.
-   */
-  bool is_reconstructed() const;
-
  private:
-  /**
-   * Match the grid-view against an earlier version of itself (if any) and copy the old UI state
-   * (e.g. active, selected, renaming, etc.) to the new one. See
-   * #AbstractGridViewItem.update_from_old().
-   */
-  void update_from_old(uiBlock &new_block);
+  void update_children_from_old(const AbstractView &old_view) override;
   AbstractGridViewItem *find_matching_item(const AbstractGridViewItem &item_to_match,
                                            const AbstractGridView &view_to_search_in) const;
   /**