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.

3 files changed, 156 insertions, 21 deletions

diff --git a/source/blender/editors/util/CMakeLists.txt b/source/blender/editors/util/CMakeLists.txt
index bbaf5d5475a..0aab3810254 100644
--- a/source/blender/editors/util/CMakeLists.txt
+++ b/source/blender/editors/util/CMakeLists.txt
@@ -39,6 +39,7 @@ set(SRC
   ed_transverts.c
   ed_util.c
   ed_util_imbuf.c
+  ed_util_ops.c
   gizmo_utils.c
   numinput.c
   select_utils.c
diff --git a/source/blender/editors/util/ed_util.c b/source/blender/editors/util/ed_util.c
index d78758dcc1c..5d2584c566d 100644
--- a/source/blender/editors/util/ed_util.c
+++ b/source/blender/editors/util/ed_util.c
@@ -485,27 +485,6 @@ void ED_spacedata_id_remap(struct ScrArea *area, struct SpaceLink *sl, ID *old_i
   }
 }
 
-static int ed_flush_edits_exec(bContext *C, wmOperator *UNUSED(op))
-{
-  Main *bmain = CTX_data_main(C);
-  ED_editors_flush_edits(bmain);
-  return OPERATOR_FINISHED;
-}
-
-void ED_OT_flush_edits(wmOperatorType *ot)
-{
-  /* identifiers */
-  ot->name = "Flush Edits";
-  ot->description = "Flush edit data from active editing modes";
-  ot->idname = "ED_OT_flush_edits";
-
-  /* api callbacks */
-  ot->exec = ed_flush_edits_exec;
-
-  /* flags */
-  ot->flag = OPTYPE_INTERNAL;
-}
-
 static bool lib_id_preview_editing_poll(bContext *C)
 {
   const PointerRNA idptr = CTX_data_pointer_get(C, "id");
diff --git a/source/blender/editors/util/ed_util_ops.c b/source/blender/editors/util/ed_util_ops.c
new file mode 100644
index 00000000000..d8d1a64c1ee
--- /dev/null
+++ b/source/blender/editors/util/ed_util_ops.c
@@ -0,0 +1,155 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup edutil
+ *
+ * Utility operators for UI data or for the UI to use.
+ */
+
+#include <string.h>
+
+#include "BLI_utildefines.h"
+
+#include "BKE_context.h"
+#include "BKE_lib_id.h"
+#include "BKE_main.h"
+#include "BKE_report.h"
+
+#include "DNA_windowmanager_types.h"
+
+#include "ED_util.h"
+
+#include "RNA_access.h"
+
+#include "UI_interface.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+static int lib_fake_user_toggle_exec(bContext *C, wmOperator *op)
+{
+  PropertyPointerRNA pprop;
+  PointerRNA idptr = PointerRNA_NULL;
+
+  UI_context_active_but_prop_get_templateID(C, &pprop.ptr, &pprop.prop);
+
+  if (pprop.prop) {
+    idptr = RNA_property_pointer_get(&pprop.ptr, pprop.prop);
+  }
+
+  if ((pprop.prop == NULL) || RNA_pointer_is_null(&idptr) || !RNA_struct_is_ID(idptr.type)) {
+    BKE_report(
+        op->reports, RPT_ERROR, "Incorrect context for running data-block fake user toggling");
+    return OPERATOR_CANCELLED;
+  }
+
+  ID *id = idptr.data;
+
+  if ((id->lib != NULL) || (ELEM(GS(id->name), ID_GR, ID_SCE, ID_SCR, ID_TXT, ID_OB, ID_WS))) {
+    BKE_report(op->reports, RPT_ERROR, "Data-block type does not support fake user");
+    return OPERATOR_CANCELLED;
+  }
+
+  if (ID_FAKE_USERS(id)) {
+    id_fake_user_clear(id);
+  }
+  else {
+    id_fake_user_set(id);
+  }
+
+  return OPERATOR_FINISHED;
+}
+
+static void ED_OT_lib_fake_user_toggle(wmOperatorType *ot)
+{
+  /* identifiers */
+  ot->name = "Toggle Fake User";
+  ot->description = "Save this data-block even if it has no users";
+  ot->idname = "ED_OT_lib_fake_user_toggle";
+
+  /* api callbacks */
+  ot->exec = lib_fake_user_toggle_exec;
+
+  /* flags */
+  ot->flag = OPTYPE_UNDO | OPTYPE_INTERNAL;
+}
+
+static int lib_unlink_exec(bContext *C, wmOperator *op)
+{
+  PropertyPointerRNA pprop;
+  PointerRNA idptr;
+
+  UI_context_active_but_prop_get_templateID(C, &pprop.ptr, &pprop.prop);
+
+  if (pprop.prop) {
+    idptr = RNA_property_pointer_get(&pprop.ptr, pprop.prop);
+  }
+
+  if ((pprop.prop == NULL) || RNA_pointer_is_null(&idptr) || !RNA_struct_is_ID(idptr.type)) {
+    BKE_report(
+        op->reports, RPT_ERROR, "Incorrect context for running data-block fake user toggling");
+    return OPERATOR_CANCELLED;
+  }
+
+  memset(&idptr, 0, sizeof(idptr));
+  RNA_property_pointer_set(&pprop.ptr, pprop.prop, idptr, NULL);
+  RNA_property_update(C, &pprop.ptr, pprop.prop);
+
+  return OPERATOR_FINISHED;
+}
+
+static void ED_OT_lib_unlink(wmOperatorType *ot)
+{
+  /* identifiers */
+  ot->name = "Unlink Data-Block";
+  ot->description = "Remove a usage of a data-block, clearing the assignment";
+  ot->idname = "ED_OT_lib_unlink";
+
+  /* api callbacks */
+  ot->exec = lib_unlink_exec;
+
+  /* flags */
+  ot->flag = OPTYPE_UNDO | OPTYPE_INTERNAL;
+}
+
+static int ed_flush_edits_exec(bContext *C, wmOperator *UNUSED(op))
+{
+  Main *bmain = CTX_data_main(C);
+  ED_editors_flush_edits(bmain);
+  return OPERATOR_FINISHED;
+}
+
+static void ED_OT_flush_edits(wmOperatorType *ot)
+{
+  /* identifiers */
+  ot->name = "Flush Edits";
+  ot->description = "Flush edit data from active editing modes";
+  ot->idname = "ED_OT_flush_edits";
+
+  /* api callbacks */
+  ot->exec = ed_flush_edits_exec;
+
+  /* flags */
+  ot->flag = OPTYPE_INTERNAL;
+}
+
+void ED_operatortypes_edutils(void)
+{
+  WM_operatortype_append(ED_OT_lib_fake_user_toggle);
+  WM_operatortype_append(ED_OT_lib_unlink);
+  WM_operatortype_append(ED_OT_flush_edits);
+}