UI: Support easy dropping into/onto rows in new tree-view API

Adds an easy way to add drop support for tree-view rows.

Most of the work is handled by the tree-view UI code. The tree items can
simply override a few functions (`can_drop()`, `on_drop()`,
`drop_tooltip()`) to implement their custom drop behavior.

While dragging over a tree-view item that can be dropped into/onto, the
item can show a custom and dynamic tooltip explaining what's gonna
happen on drop.

This isn't used yet, but will soon be for asset catalogs.

See documentation here:
https://wiki.blender.org/wiki/Source/Interface/Views#Further_Customizations

1 files changed, 9 insertions, 0 deletions

diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index 106f6166760..f642895f64e 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -2593,6 +2593,7 @@ typedef struct uiDragColorHandle {
 
 void ED_operatortypes_ui(void);
 void ED_keymap_ui(struct wmKeyConfig *keyconf);
+void ED_dropboxes_ui(void);
 void ED_uilisttypes_ui(void);
 
 void UI_drop_color_copy(struct wmDrag *drag, struct wmDropBox *drop);
@@ -2763,6 +2764,14 @@ void UI_interface_tag_script_reload(void);
 
 bool UI_tree_view_item_is_active(const uiTreeViewItemHandle *item);
 bool UI_tree_view_item_matches(const uiTreeViewItemHandle *a, const uiTreeViewItemHandle *b);
+bool UI_tree_view_item_can_drop(const uiTreeViewItemHandle *item_, const struct wmDrag *drag);
+bool UI_tree_view_item_drop_handle(uiTreeViewItemHandle *item_, const struct ListBase *drags);
+char *UI_tree_view_item_drop_tooltip(const uiTreeViewItemHandle *item,
+                                     const struct bContext *C,
+                                     const struct wmDrag *drag,
+                                     const struct wmEvent *event);
+
+uiTreeViewItemHandle *UI_block_tree_view_find_item_at(const struct ARegion *region, int x, int y);
 
 #ifdef __cplusplus
 }