UI: Tree-View API for easy creation of tree UIs

This follows three main targets:

* Make creation of new tree UIs easy.
* Groundwork to generalize tree UIs (so e.g. Outliner, animation
  channels, asset catalogs and spreadsheet data-sets don't have to
  re-implement basic tree UI code) or even other data-view UIs.
* Better separate data and UI state. E.g. with this, tree-item selection
  or the open/collapsed state can be stored on the UI level, rather than
  in data. (Asset Catalogs need this, storing UI state info in them is
  not an option.)

In addition, the design should be well testable and could even be
exposed to Python.

Note that things will likely change in master still. E.g. the actually
resulting UI isn't very nice visually yet.

The design is documented here:
https://wiki.blender.org/wiki/Source/Interface/Views

Differential Revision: https://developer.blender.org/D12573

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 916105b0f8e..f7842270746 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -84,6 +84,10 @@ typedef struct uiBlock uiBlock;
 typedef struct uiBut uiBut;
 typedef struct uiLayout uiLayout;
 typedef struct uiPopupBlockHandle uiPopupBlockHandle;
+/* C handle for C++ #ui::AbstractTreeView type. */
+typedef struct uiTreeViewHandle uiTreeViewHandle;
+/* C handle for C++ #ui::AbstractTreeViewItem type. */
+typedef struct uiTreeViewItemHandle uiTreeViewItemHandle;
 
 /* Defines */
 
@@ -389,6 +393,8 @@ typedef enum {
   UI_BTYPE_GRIP = 57 << 9,
   UI_BTYPE_DECORATOR = 58 << 9,
   UI_BTYPE_DATASETROW = 59 << 9,
+  /* An item in a tree view. Parent items may be collapsible. */
+  UI_BTYPE_TREEROW = 60 << 9,
 } eButType;
 
 #define BUTTYPE (63 << 9)
@@ -1672,6 +1678,7 @@ void UI_but_datasetrow_component_set(uiBut *but, uint8_t geometry_component_type
 void UI_but_datasetrow_domain_set(uiBut *but, uint8_t attribute_domain);
 uint8_t UI_but_datasetrow_component_get(uiBut *but);
 uint8_t UI_but_datasetrow_domain_get(uiBut *but);
+void UI_but_treerow_indentation_set(uiBut *but, int indentation);
 
 void UI_but_node_link_set(uiBut *but, struct bNodeSocket *socket, const float draw_color[4]);
 
@@ -2754,6 +2761,8 @@ void UI_interface_tag_script_reload(void);
 /* Support click-drag motion which presses the button and closes a popover (like a menu). */
 #define USE_UI_POPOVER_ONCE
 
+bool UI_tree_view_item_is_active(uiTreeViewItemHandle *item_);
+
 #ifdef __cplusplus
 }
 #endif