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, 39 insertions, 4 deletions

diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index fd75be5b847..beee622673c 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -856,10 +856,21 @@ static void ui_but_update_old_active_from_new(uiBut *oldbut, uiBut *but)
     oldbut->hardmax = but->hardmax;
   }
 
-  if (oldbut->type == UI_BTYPE_PROGRESS_BAR) {
-    uiButProgressbar *progress_oldbut = (uiButProgressbar *)oldbut;
-    uiButProgressbar *progress_but = (uiButProgressbar *)but;
-    progress_oldbut->progress = progress_but->progress;
+  switch (oldbut->type) {
+    case UI_BTYPE_PROGRESS_BAR: {
+      uiButProgressbar *progress_oldbut = (uiButProgressbar *)oldbut;
+      uiButProgressbar *progress_but = (uiButProgressbar *)but;
+      progress_oldbut->progress = progress_but->progress;
+      break;
+    }
+    case UI_BTYPE_TREEROW: {
+      uiButTreeRow *treerow_oldbut = (uiButTreeRow *)oldbut;
+      uiButTreeRow *treerow_newbut = (uiButTreeRow *)but;
+      SWAP(uiTreeViewItemHandle *, treerow_newbut->tree_item, treerow_oldbut->tree_item);
+      break;
+    }
+    default:
+      break;
   }
 
   /* move/copy string from the new button to the old */
@@ -2203,6 +2214,15 @@ int ui_but_is_pushed_ex(uiBut *but, double *value)
           }
         }
         break;
+      case UI_BTYPE_TREEROW: {
+        uiButTreeRow *tree_row_but = (uiButTreeRow *)but;
+
+        is_push = -1;
+        if (tree_row_but->tree_item) {
+          is_push = UI_tree_view_item_is_active(tree_row_but->tree_item);
+        }
+        break;
+      }
       default:
         is_push = -1;
         break;
@@ -3447,6 +3467,7 @@ void UI_block_free(const bContext *C, uiBlock *block)
   BLI_freelistN(&block->color_pickers.list);
 
   ui_block_free_button_groups(block);
+  ui_block_free_views(block);
 
   MEM_freeN(block);
 }
@@ -3942,6 +3963,10 @@ static void ui_but_alloc_info(const eButType type,
       alloc_size = sizeof(uiButDatasetRow);
       alloc_str = "uiButDatasetRow";
       break;
+    case UI_BTYPE_TREEROW:
+      alloc_size = sizeof(uiButTreeRow);
+      alloc_str = "uiButTreeRow";
+      break;
     default:
       alloc_size = sizeof(uiBut);
       alloc_str = "uiBut";
@@ -4141,6 +4166,7 @@ static uiBut *ui_def_but(uiBlock *block,
                 UI_BTYPE_BUT_MENU,
                 UI_BTYPE_SEARCH_MENU,
                 UI_BTYPE_DATASETROW,
+                UI_BTYPE_TREEROW,
                 UI_BTYPE_POPOVER)) {
     but->drawflag |= (UI_BUT_TEXT_LEFT | UI_BUT_ICON_LEFT);
   }
@@ -6878,6 +6904,15 @@ void UI_but_datasetrow_indentation_set(uiBut *but, int indentation)
   BLI_assert(indentation >= 0);
 }
 
+void UI_but_treerow_indentation_set(uiBut *but, int indentation)
+{
+  uiButTreeRow *but_row = (uiButTreeRow *)but;
+  BLI_assert(but->type == UI_BTYPE_TREEROW);
+
+  but_row->indentation = indentation;
+  BLI_assert(indentation >= 0);
+}
+
 /**
  * Adds a hint to the button which draws right aligned, grayed out and never clipped.
  */