UI: Better split layout support for checkboxes

Makes the following layout changes possible:
{F8473498} {F8473499} {F8473502}

The next commit will contain many layout changes to make good use of
these new possibilities. The result should be more consistent, easier to
read and should give a more organized impression. Additionally, it
should be possible to replace many sub-panels with compacter layouts.

Main changes:
* Checkboxes now respect the property split layouts
* Add support for row and column headers (i.e.
  `uiLayout.column(heading="Foo")`, `uiLayout.row(heading="Bar")`). If the
  first property added to this layout doesn't insert anything into the label
  split column, the heading is inserted there. Otherwise, it's inserted as own
  item.
* Add support for manually inserting decorators for an existing item
  (`uiLayout.prop_decorator()`). That way layout creators can manually insert
  this, which was the only way I saw to support property split layouts with a
  checkbox before the actual property. {F8471883}
* Autogenerated layouts for operator properties look bad if there are only
  checkboxes (which only use half the region width). So before creating the
  layout, we iterate over visible properties and disable split layout if all
  are booleans. I think this is fine, if needed we could also add layout hints
  to operators.
* `uiTemplateOperatorPropertyButs()` now handles macros itself, the caller
  used to be responsible for this. Code that didn't handle these so far never
  used macros I think, so this change should be invisible.
* Remove manual property split layout from autogenerated operator properties
  layout.
* Padding of checkboxes is tweaked to make their label visually more connected
  to the checkboxes.
* Support split layout for menus (should work for `uiLayout.menu()`,
  `.operator_menu_enum()`, `.prop_menu_enum()`, maybe more)

Maniphest Task: https://developer.blender.org/T65965

Differential Revision: https://developer.blender.org/D7427

Reviewed by: Brecht Van Lommel, William Reynish, Pablo Vazques

1 files changed, 28 insertions, 2 deletions

diff --git a/source/blender/makesrna/intern/rna_ui_api.c b/source/blender/makesrna/intern/rna_ui_api.c
index deab353841f..2a64ffa73cd 100644
--- a/source/blender/makesrna/intern/rna_ui_api.c
+++ b/source/blender/makesrna/intern/rna_ui_api.c
@@ -693,7 +693,7 @@ void RNA_api_ui_layout(StructRNA *srna)
   static float node_socket_color_default[] = {0.0f, 0.0f, 0.0f, 1.0f};
 
   /* simple layout specifiers */
-  func = RNA_def_function(srna, "row", "uiLayoutRow");
+  func = RNA_def_function(srna, "row", "uiLayoutRowWithHeading");
   parm = RNA_def_pointer(func, "layout", "UILayout", "", "Sub-layout to put items in");
   RNA_def_function_return(func, parm);
   RNA_def_function_ui_description(
@@ -701,8 +701,14 @@ void RNA_api_ui_layout(StructRNA *srna)
       "Sub-layout. Items placed in this sublayout are placed next to each other "
       "in a row");
   RNA_def_boolean(func, "align", false, "", "Align buttons to each other");
+  RNA_def_string(func,
+                 "heading",
+                 NULL,
+                 UI_MAX_NAME_STR,
+                 "Heading",
+                 "Label to insert into the layout for this row");
 
-  func = RNA_def_function(srna, "column", "uiLayoutColumn");
+  func = RNA_def_function(srna, "column", "uiLayoutColumnWithHeading");
   parm = RNA_def_pointer(func, "layout", "UILayout", "", "Sub-layout to put items in");
   RNA_def_function_return(func, parm);
   RNA_def_function_ui_description(
@@ -710,6 +716,12 @@ void RNA_api_ui_layout(StructRNA *srna)
       "Sub-layout. Items placed in this sublayout are placed under each other "
       "in a column");
   RNA_def_boolean(func, "align", false, "", "Align buttons to each other");
+  RNA_def_string(func,
+                 "heading",
+                 NULL,
+                 UI_MAX_NAME_STR,
+                 "Heading",
+                 "Label to insert into the layout for this column");
 
   func = RNA_def_function(srna, "column_flow", "uiLayoutColumnFlow");
   RNA_def_int(func, "columns", 0, 0, INT_MAX, "", "Number of columns, 0 is automatic", 0, INT_MAX);
@@ -887,6 +899,20 @@ void RNA_api_ui_layout(StructRNA *srna)
   RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
   api_ui_item_common(func);
 
+  func = RNA_def_function(srna, "prop_decorator", "uiItemDecoratorR");
+  api_ui_item_rna_common(func);
+  RNA_def_int(func,
+              "index",
+              /* RNA_NO_INDEX == -1 */
+              -1,
+              -2,
+              INT_MAX,
+              "",
+              "The index of this button, when set a single member of an array can be accessed, "
+              "when set to -1 all array members are used",
+              -2,
+              INT_MAX);
+
   for (int is_menu_hold = 0; is_menu_hold < 2; is_menu_hold++) {
     func = (is_menu_hold) ? RNA_def_function(srna, "operator_menu_hold", "rna_uiItemOMenuHold") :
                             RNA_def_function(srna, "operator", "rna_uiItemO");