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, 30 insertions, 7 deletions

diff --git a/source/blender/editors/interface/interface_widgets.c b/source/blender/editors/interface/interface_widgets.c
index 0dc7c2d3f9a..375206cab44 100644
--- a/source/blender/editors/interface/interface_widgets.c
+++ b/source/blender/editors/interface/interface_widgets.c
@@ -115,6 +115,7 @@ typedef enum {
   UI_WTYPE_PROGRESSBAR,
   UI_WTYPE_NODESOCKET,
   UI_WTYPE_DATASETROW,
+  UI_WTYPE_TREEROW,
 } uiWidgetTypeEnum;
 
 /* Button state argument shares bits with 'uiBut.flag'.
@@ -3679,10 +3680,9 @@ static void widget_progressbar(
   widgetbase_draw(&wtb_bar, wcol);
 }
 
-static void widget_datasetrow(
-    uiBut *but, uiWidgetColors *wcol, rcti *rect, int state, int UNUSED(roundboxalign))
+static void widget_treerow_exec(
+    uiWidgetColors *wcol, rcti *rect, int state, int UNUSED(roundboxalign), int indentation)
 {
-  uiButDatasetRow *but_componentrow = (uiButDatasetRow *)but;
   uiWidgetBase wtb;
   widget_init(&wtb);
 
@@ -3695,10 +3695,24 @@ static void widget_datasetrow(
     widgetbase_draw(&wtb, wcol);
   }
 
-  BLI_rcti_resize(rect,
-                  BLI_rcti_size_x(rect) - UI_UNIT_X * but_componentrow->indentation,
-                  BLI_rcti_size_y(rect));
-  BLI_rcti_translate(rect, 0.5f * UI_UNIT_X * but_componentrow->indentation, 0);
+  BLI_rcti_resize(rect, BLI_rcti_size_x(rect) - UI_UNIT_X * indentation, BLI_rcti_size_y(rect));
+  BLI_rcti_translate(rect, 0.5f * UI_UNIT_X * indentation, 0);
+}
+
+static void widget_treerow(
+    uiBut *but, uiWidgetColors *wcol, rcti *rect, int state, int roundboxalign)
+{
+  uiButTreeRow *tree_row = (uiButTreeRow *)but;
+  BLI_assert(but->type == UI_BTYPE_TREEROW);
+  widget_treerow_exec(wcol, rect, state, roundboxalign, tree_row->indentation);
+}
+
+static void widget_datasetrow(
+    uiBut *but, uiWidgetColors *wcol, rcti *rect, int state, int roundboxalign)
+{
+  uiButDatasetRow *dataset_row = (uiButDatasetRow *)but;
+  BLI_assert(but->type == UI_BTYPE_DATASETROW);
+  widget_treerow_exec(wcol, rect, state, roundboxalign, dataset_row->indentation);
 }
 
 static void widget_nodesocket(
@@ -4492,6 +4506,10 @@ static uiWidgetType *widget_type(uiWidgetTypeEnum type)
       wt.custom = widget_datasetrow;
       break;
 
+    case UI_WTYPE_TREEROW:
+      wt.custom = widget_treerow;
+      break;
+
     case UI_WTYPE_NODESOCKET:
       wt.custom = widget_nodesocket;
       break;
@@ -4824,6 +4842,11 @@ void ui_draw_but(const bContext *C, struct ARegion *region, uiStyle *style, uiBu
         fstyle = &style->widgetlabel;
         break;
 
+      case UI_BTYPE_TREEROW:
+        wt = widget_type(UI_WTYPE_TREEROW);
+        fstyle = &style->widgetlabel;
+        break;
+
       case UI_BTYPE_SCROLL:
         wt = widget_type(UI_WTYPE_SCROLL);
         break;