UI: Add AbstractViewItem base class

No user visible changes expected.

Similar to rBc355be6faeac, but for view items now instead of the view.
Not much of the item code is ported to use it yet, it's actually a bit
tricky for the most part. But just introducing the base class already
allows me to start unifying the view item buttons (`uiButTreeRow` and
`uiButGridTile`). This would be a nice improvement.

1 files changed, 27 insertions, 0 deletions

diff --git a/source/blender/editors/include/UI_abstract_view.hh b/source/blender/editors/include/UI_abstract_view.hh
index 82f81f1702b..fdb7069e7c4 100644
--- a/source/blender/editors/include/UI_abstract_view.hh
+++ b/source/blender/editors/include/UI_abstract_view.hh
@@ -15,12 +15,17 @@
 #include <array>
 #include <memory>
 
+#include "DNA_defs.h"
+
 #include "BLI_span.hh"
 
 struct wmNotifier;
+struct uiBlock;
 
 namespace blender::ui {
 
+class AbstractViewItem;
+
 class AbstractView {
   bool is_reconstructed_ = false;
   /**
@@ -66,4 +71,26 @@ class AbstractView {
   bool is_reconstructed() const;
 };
 
+class AbstractViewItem {
+ protected:
+  bool is_active_ = false;
+
+ public:
+  virtual ~AbstractViewItem() = default;
+
+ protected:
+  AbstractViewItem() = default;
+
+  /**
+   * Copy persistent state (e.g. active, selection, etc.) from a matching item of
+   * the last redraw to this item. If sub-classes introduce more advanced state they should
+   * override this and make it update their state accordingly.
+   *
+   * \note Always call the base class implementation when overriding this!
+   */
+  virtual void update_from_old(const AbstractViewItem &old);
+
+  void set_view(AbstractView &view);
+};
+
 }  // namespace blender::ui