UI: Redesigned data-block selectors

The previous design is rather old and has a couple of problems:

* Scalability: The current solution of adding little icon buttons next to the
  data-block name field doesn't scale well. It only works if there's a small
  number of operations. We need to be able to place more items there for better
  data-block management. Especially with the introduction of library overrides.
* Discoverability: It's not obvious what some of the icons do. They appear and
  disappear, but it's not obvious why some are available at times and others
  not.
* Unclear Status: Currently their library status (linked, indirectly linked,
  broken link, library override) isn't really clear.
* Unusual behavior: Some of the icon buttons allow Shift or Ctrl clicking to
  invoke alternative behaviors. This is not a usual pattern in Blender.

This patch does the following changes:

* Adds a menu to the right of the name button to access all kinds of operations
  (create, delete, unlink, user management, library overrides, etc).
* Make good use of the "disabled hint" for tooltips, to explain why buttons are
  disabled. The UI team wants to establish this as a good practise.
* Use superimposed icons for duplicate and unlink, rather than extra buttons
  (uses less space, looks less distracting and is a nice + consistent design
  language).
* Remove fake user and user count button, they are available from the menu now.
* Support tooltips for superimposed icons (committed mouse hover feedback to
  master already).
* Slightly increase size of the name button - it was already a bit small
  before, and the move from real buttons to superimposed icons reduces usable
  space for the name itself.
* More clearly differentiate between duplicate and creating a new data-block.
  The latter is only available in the menu.
* Display library status icon on the left (linked, missing library, overridden,
  asset)
* Disables "Make Single User" button - in review we weren't sure if there are
  good use-cases for it, so better to see if we can remove it.

Note that I do expect some aspects of this design to change still. I think some
changes are problematic, but others disagreed. I will open a feedback thread on
devtalk to see what others think.

Differential Revision: https://developer.blender.org/D8554

Reviewed by: Bastien Montagne

Design discussed and agreed on with the UI team, also see T79959.

1 files changed, 7 insertions, 2 deletions

diff --git a/source/blender/makesrna/intern/rna_ui_api.c b/source/blender/makesrna/intern/rna_ui_api.c
index 447f5b4210b..e26cc8d8d41 100644
--- a/source/blender/makesrna/intern/rna_ui_api.c
+++ b/source/blender/makesrna/intern/rna_ui_api.c
@@ -480,6 +480,7 @@ static void rna_uiTemplateID(uiLayout *layout,
                              PointerRNA *ptr,
                              const char *propname,
                              const char *newop,
+                             const char *duplicateop,
                              const char *openop,
                              const char *unlinkop,
                              int filter,
@@ -498,7 +499,8 @@ static void rna_uiTemplateID(uiLayout *layout,
   /* Get translated name (label). */
   name = rna_translate_ui_text(name, text_ctxt, NULL, prop, translate);
 
-  uiTemplateID(layout, C, ptr, propname, newop, openop, unlinkop, filter, live_icon, name);
+  uiTemplateID(
+      layout, C, ptr, propname, newop, duplicateop, openop, unlinkop, filter, live_icon, name);
 }
 
 static void rna_uiTemplateAnyID(uiLayout *layout,
@@ -1156,8 +1158,11 @@ void RNA_api_ui_layout(StructRNA *srna)
   api_ui_item_rna_common(func);
   RNA_def_string(func, "new", NULL, 0, "", "Operator identifier to create a new ID block");
   RNA_def_string(
+      func, "duplicate", NULL, 0, "", "Operator identifier to duplicate the selected ID block");
+  RNA_def_string(
       func, "open", NULL, 0, "", "Operator identifier to open a file for creating a new ID block");
-  RNA_def_string(func, "unlink", NULL, 0, "", "Operator identifier to unlink the ID block");
+  RNA_def_string(
+      func, "unlink", NULL, 0, "", "Operator identifier to unlink the selected ID block");
   RNA_def_enum(func,
                "filter",
                id_template_filter_items,