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, 120 insertions, 61 deletions

diff --git a/source/blender/editors/space_action/action_data.c b/source/blender/editors/space_action/action_data.c
index 3a584a7f0cb..4d5a93f75e0 100644
--- a/source/blender/editors/space_action/action_data.c
+++ b/source/blender/editors/space_action/action_data.c
@@ -158,7 +158,78 @@ static void actedit_change_action(bContext *C, bAction *act)
   RNA_property_update(C, &ptr, prop);
 }
 
-/* ******************** New Action Operator *********************** */
+/* ******************** New Action Operators *********************** */
+
+static void action_creation_assign(bContext *C,
+                                   bAction *action,
+                                   PointerRNA *ptr,
+                                   PropertyRNA *prop)
+{
+  PointerRNA idptr;
+  /* Set the new action.
+   * NOTE: we can't use actedit_change_action, as this function is also called from the NLA. */
+  RNA_id_pointer_create(&action->id, &idptr);
+  RNA_property_pointer_set(ptr, prop, idptr, NULL);
+  RNA_property_update(C, ptr, prop);
+}
+
+/**
+ * Stash the previously active action to prevent it from being lost.
+ * \return The old action if any.
+ */
+static bAction *action_creation_stash_old(bContext *C, PointerRNA *ptr, PropertyRNA *prop)
+{
+  bAction *oldact = NULL;
+  AnimData *adt = NULL;
+
+  if (prop) {
+    /* The operator was called from a button. */
+    PointerRNA oldptr;
+
+    oldptr = RNA_property_pointer_get(ptr, prop);
+    oldact = (bAction *)oldptr.owner_id;
+
+    /* stash the old action to prevent it from being lost */
+    if (ptr->type == &RNA_AnimData) {
+      adt = ptr->data;
+    }
+    else if (ptr->type == &RNA_SpaceDopeSheetEditor) {
+      adt = ED_actedit_animdata_from_context(C);
+    }
+  }
+  else {
+    adt = ED_actedit_animdata_from_context(C);
+    oldact = adt->action;
+  }
+
+  if (!adt || !oldact) {
+    /* Found nothing to stash in current context. */
+    return NULL;
+  }
+
+  /* Perform stashing operation. */
+  if (BKE_nla_action_stash(adt, ID_IS_OVERRIDE_LIBRARY(ptr->owner_id))) {
+    /* The stash operation will remove the user already
+     * (and unlink the action from the AnimData action slot).
+     * Hence, we must unset the ref to the action in the
+     * action editor too (if this is where we're being called from)
+     * first before setting the new action once it is created,
+     * or else the user gets decremented twice!
+     */
+    if (ptr->type == &RNA_SpaceDopeSheetEditor) {
+      SpaceAction *saction = ptr->data;
+      saction->action = NULL;
+    }
+  }
+  else {
+#if 0
+    printf("WARNING: Failed to stash %s. It may already exist in the NLA stack though\n",
+           oldact->id.name);
+#endif
+  }
+
+  return oldact;
+}
 
 /* Criteria:
  *  1) There must be an dopesheet/action editor, and it must be in a mode which uses actions...
@@ -207,71 +278,17 @@ static bool action_new_poll(bContext *C)
 
 static int action_new_exec(bContext *C, wmOperator *UNUSED(op))
 {
-  PointerRNA ptr, idptr;
+  PointerRNA ptr;
   PropertyRNA *prop;
 
-  bAction *oldact = NULL;
-  AnimData *adt = NULL;
   /* hook into UI */
   UI_context_active_but_prop_get_templateID(C, &ptr, &prop);
 
-  if (prop) {
-    /* The operator was called from a button. */
-    PointerRNA oldptr;
-
-    oldptr = RNA_property_pointer_get(&ptr, prop);
-    oldact = (bAction *)oldptr.owner_id;
-
-    /* stash the old action to prevent it from being lost */
-    if (ptr.type == &RNA_AnimData) {
-      adt = ptr.data;
-    }
-    else if (ptr.type == &RNA_SpaceDopeSheetEditor) {
-      adt = ED_actedit_animdata_from_context(C);
-    }
-  }
-  else {
-    adt = ED_actedit_animdata_from_context(C);
-    oldact = adt->action;
-  }
-  {
-    bAction *action = NULL;
-
-    /* Perform stashing operation - But only if there is an action */
-    if (adt && oldact) {
-      /* stash the action */
-      if (BKE_nla_action_stash(adt, ID_IS_OVERRIDE_LIBRARY(ptr.owner_id))) {
-        /* The stash operation will remove the user already
-         * (and unlink the action from the AnimData action slot).
-         * Hence, we must unset the ref to the action in the
-         * action editor too (if this is where we're being called from)
-         * first before setting the new action once it is created,
-         * or else the user gets decremented twice!
-         */
-        if (ptr.type == &RNA_SpaceDopeSheetEditor) {
-          SpaceAction *saction = ptr.data;
-          saction->action = NULL;
-        }
-      }
-      else {
-#if 0
-        printf("WARNING: Failed to stash %s. It may already exist in the NLA stack though\n",
-               oldact->id.name);
-#endif
-      }
-    }
-
-    /* create action */
-    action = action_create_new(C, oldact);
+  action_creation_stash_old(C, &ptr, prop);
 
-    if (prop) {
-      /* set this new action
-       * NOTE: we can't use actedit_change_action, as this function is also called from the NLA
-       */
-      RNA_id_pointer_create(&action->id, &idptr);
-      RNA_property_pointer_set(&ptr, prop, idptr, NULL);
-      RNA_property_update(C, &ptr, prop);
-    }
+  bAction *action = action_create_new(C, NULL);
+  if (prop) {
+    action_creation_assign(C, action, &ptr, prop);
   }
 
   /* set notifier that keyframes have changed */
@@ -285,7 +302,7 @@ void ACTION_OT_new(wmOperatorType *ot)
   /* identifiers */
   ot->name = "New Action";
   ot->idname = "ACTION_OT_new";
-  ot->description = "Create new action";
+  ot->description = "Create a new action";
 
   /* api callbacks */
   ot->exec = action_new_exec;
@@ -295,6 +312,45 @@ void ACTION_OT_new(wmOperatorType *ot)
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+static int action_duplicate_assign_exec(bContext *C, wmOperator *UNUSED(op))
+{
+  PointerRNA ptr;
+  PropertyRNA *prop;
+
+  /* hook into UI */
+  UI_context_active_but_prop_get_templateID(C, &ptr, &prop);
+
+  bAction *old_action = action_creation_stash_old(C, &ptr, prop);
+
+  bAction *new_action = action_create_new(C, old_action);
+  if (prop) {
+    action_creation_assign(C, new_action, &ptr, prop);
+  }
+
+  /* set notifier that keyframes have changed */
+  WM_event_add_notifier(C, NC_ANIMATION | ND_KEYFRAME | NA_ADDED, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+/**
+ * Duplicate an action assigned to a templateID and update it's assignment - based on UI context.
+ */
+void ACTION_OT_duplicate_assign(wmOperatorType *ot)
+{
+  /* identifiers */
+  ot->name = "Duplicate & Assign Action";
+  ot->idname = "ACTION_OT_duplicate_assign";
+  ot->description = "Create a copy of an existing action and assign it";
+
+  /* api callbacks */
+  ot->exec = action_duplicate_assign_exec;
+  ot->poll = action_new_poll;
+
+  /* flags */
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO | OPTYPE_INTERNAL;
+}
+
 /* ******************* Action Push-Down Operator ******************** */
 
 /* Criteria:
diff --git a/source/blender/editors/space_action/action_intern.h b/source/blender/editors/space_action/action_intern.h
index ffe0606c98f..4bce6c62a1a 100644
--- a/source/blender/editors/space_action/action_intern.h
+++ b/source/blender/editors/space_action/action_intern.h
@@ -106,6 +106,7 @@ void ACTION_OT_snap(struct wmOperatorType *ot);
 void ACTION_OT_mirror(struct wmOperatorType *ot);
 
 void ACTION_OT_new(struct wmOperatorType *ot);
+void ACTION_OT_duplicate_assign(struct wmOperatorType *ot);
 void ACTION_OT_unlink(struct wmOperatorType *ot);
 
 void ACTION_OT_push_down(struct wmOperatorType *ot);
diff --git a/source/blender/editors/space_action/action_ops.c b/source/blender/editors/space_action/action_ops.c
index 7422c05511c..329c3a9f6f6 100644
--- a/source/blender/editors/space_action/action_ops.c
+++ b/source/blender/editors/space_action/action_ops.c
@@ -73,7 +73,9 @@ void action_operatortypes(void)
   WM_operatortype_append(ACTION_OT_copy);
   WM_operatortype_append(ACTION_OT_paste);
 
+  /* UI-context based operators. */
   WM_operatortype_append(ACTION_OT_new);
+  WM_operatortype_append(ACTION_OT_duplicate_assign);
   WM_operatortype_append(ACTION_OT_unlink);
 
   WM_operatortype_append(ACTION_OT_push_down);