Outliner: Refactor element warning and mode column querying

Uses a inheritance based approach for querying warning of tree elements
and the mode column support of display modes.

For the warnings, tree elements can override the
`AbstractTreeElement::getWarning()` method and return a warning string.
The UI will draw the warning column with warning icons. This makes the
warning column more generalized and easier to extend to more use-cases.
E.g. library override elements will use this after a followup commit.

To support mode toggles a display mode can now just return true in the
`AbstractTreeDisplay::supportsModeColumn()` method. This makes it
trivial to add mode columns to other display modes, and less error prone
because there's no need to hunt down a bunch of display mode checks in
different places.

15 files changed, 129 insertions, 88 deletions

diff --git a/source/blender/editors/space_outliner/CMakeLists.txt b/source/blender/editors/space_outliner/CMakeLists.txt
index 59f6bd85d59..1c09ad2d98f 100644
--- a/source/blender/editors/space_outliner/CMakeLists.txt
+++ b/source/blender/editors/space_outliner/CMakeLists.txt
@@ -27,6 +27,7 @@ set(SRC
   outliner_draw.cc
   outliner_edit.cc
   outliner_ops.cc
+  outliner_query.cc
   outliner_select.cc
   outliner_sync.cc
   outliner_tools.cc
diff --git a/source/blender/editors/space_outliner/outliner_draw.cc b/source/blender/editors/space_outliner/outliner_draw.cc
index d165e98d7d4..daa1cbdccdb 100644
--- a/source/blender/editors/space_outliner/outliner_draw.cc
+++ b/source/blender/editors/space_outliner/outliner_draw.cc
@@ -72,6 +72,7 @@
 #include "tree/tree_element_overrides.hh"
 #include "tree/tree_element_rna.hh"
 
+using namespace blender;
 using namespace blender::ed::outliner;
 
 /* -------------------------------------------------------------------- */
@@ -2285,19 +2286,19 @@ static void outliner_draw_mode_column(const bContext *C,
 static bool outliner_draw_warning_tree_element(uiBlock *block,
                                                SpaceOutliner *space_outliner,
                                                TreeElement *te,
-                                               TreeStoreElem *tselem,
                                                const bool use_mode_column,
                                                const int te_ys)
 {
-  if ((te->flag & TE_HAS_WARNING) == 0) {
-    /* If given element has no warning, recursively try to display the first sub-elements' warning.
+  const AbstractTreeElement *abstract_te = tree_element_cast<AbstractTreeElement>(te);
+  const StringRefNull warning_msg = abstract_te ? abstract_te->getWarning() : "";
+
+  if (warning_msg.is_empty()) {
+    /* If given element has no warning, recursively try to display the first sub-element's warning.
      */
-    if (!TSELEM_OPEN(tselem, space_outliner)) {
+    if (!TSELEM_OPEN(te->store_elem, space_outliner)) {
       LISTBASE_FOREACH (TreeElement *, sub_te, &te->subtree) {
-        TreeStoreElem *sub_tselem = TREESTORE(sub_te);
-
         if (outliner_draw_warning_tree_element(
-                block, space_outliner, sub_te, sub_tselem, use_mode_column, te_ys)) {
+                block, space_outliner, sub_te, use_mode_column, te_ys)) {
           return true;
         }
       }
@@ -2305,12 +2306,6 @@ static bool outliner_draw_warning_tree_element(uiBlock *block,
     return false;
   }
 
-  int icon = ICON_NONE;
-  const char *tip = "";
-  const bool has_warning = tree_element_warnings_get(te, &icon, &tip);
-  BLI_assert(has_warning);
-  UNUSED_VARS_NDEBUG(has_warning);
-
   /* Move the warnings a unit left in view layer mode. */
   const short mode_column_offset = (use_mode_column && (space_outliner->outlinevis == SO_SCENES)) ?
                                        UI_UNIT_X :
@@ -2320,7 +2315,7 @@ static bool outliner_draw_warning_tree_element(uiBlock *block,
   uiBut *but = uiDefIconBut(block,
                             UI_BTYPE_ICON_TOGGLE,
                             0,
-                            icon,
+                            ICON_ERROR,
                             mode_column_offset,
                             te_ys,
                             UI_UNIT_X,
@@ -2330,7 +2325,7 @@ static bool outliner_draw_warning_tree_element(uiBlock *block,
                             0.0,
                             0.0,
                             0.0,
-                            tip);
+                            warning_msg.c_str());
   /* No need for undo here, this is a pure info widget. */
   UI_but_flag_disable(but, UI_BUT_UNDO);
 
@@ -2344,11 +2339,9 @@ static void outliner_draw_warning_column(const bContext *C,
                                          ListBase *tree)
 {
   LISTBASE_FOREACH (TreeElement *, te, tree) {
-    TreeStoreElem *tselem = TREESTORE(te);
-
-    outliner_draw_warning_tree_element(block, space_outliner, te, tselem, use_mode_column, te->ys);
+    outliner_draw_warning_tree_element(block, space_outliner, te, use_mode_column, te->ys);
 
-    if (TSELEM_OPEN(tselem, space_outliner)) {
+    if (TSELEM_OPEN(te->store_elem, space_outliner)) {
       outliner_draw_warning_column(C, block, space_outliner, use_mode_column, &te->subtree);
     }
   }
@@ -3961,13 +3954,8 @@ void draw_outliner(const bContext *C)
   UI_view2d_view_ortho(v2d);
 
   /* Only show mode column in View Layers and Scenes view. */
-  const bool use_mode_column = (space_outliner->flag & SO_MODE_COLUMN) &&
-                               (ELEM(space_outliner->outlinevis, SO_VIEW_LAYER, SO_SCENES));
-
-  const bool use_warning_column = ELEM(space_outliner->outlinevis,
-                                       SO_LIBRARIES,
-                                       SO_OVERRIDES_LIBRARY) &&
-                                  space_outliner->runtime->tree_display->hasWarnings();
+  const bool use_mode_column = outliner_shows_mode_column(*space_outliner);
+  const bool use_warning_column = outliner_has_element_warnings(*space_outliner);
 
   /* Draw outliner stuff (background, hierarchy lines and names). */
   const float right_column_width = outliner_right_columns_width(space_outliner);
diff --git a/source/blender/editors/space_outliner/outliner_intern.hh b/source/blender/editors/space_outliner/outliner_intern.hh
index f3bcb7b0f1e..190b8f2fe36 100644
--- a/source/blender/editors/space_outliner/outliner_intern.hh
+++ b/source/blender/editors/space_outliner/outliner_intern.hh
@@ -160,8 +160,6 @@ enum {
   /* Child elements of the same type in the icon-row are drawn merged as one icon.
    * This flag is set for an element that is part of these merged child icons. */
   TE_ICONROW_MERGED = (1 << 7),
-  /* This element has some warning to be displayed. */
-  TE_HAS_WARNING = (1 << 8),
 };
 
 /* button events */
@@ -510,6 +508,11 @@ void OUTLINER_OT_drivers_delete_selected(struct wmOperatorType *ot);
 
 void OUTLINER_OT_orphans_purge(struct wmOperatorType *ot);
 
+/* outliner_query.cc ---------------------------------------------- */
+
+bool outliner_shows_mode_column(const SpaceOutliner &space_outliner);
+bool outliner_has_element_warnings(const SpaceOutliner &space_outliner);
+
 /* outliner_tools.c ---------------------------------------------- */
 
 void merged_element_search_menu_invoke(struct bContext *C,
diff --git a/source/blender/editors/space_outliner/outliner_query.cc b/source/blender/editors/space_outliner/outliner_query.cc
new file mode 100644
index 00000000000..d6483c44fce
--- /dev/null
+++ b/source/blender/editors/space_outliner/outliner_query.cc
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup spoutliner
+ */
+
+#include <functional>
+
+#include "BLI_listbase.h"
+
+#include "DNA_space_types.h"
+
+#include "outliner_intern.hh"
+#include "tree/tree_display.hh"
+
+using namespace blender::ed::outliner;
+
+bool outliner_shows_mode_column(const SpaceOutliner &space_outliner)
+{
+  const AbstractTreeDisplay &tree_display = *space_outliner.runtime->tree_display;
+
+  return tree_display.supportsModeColumn() && (space_outliner.flag & SO_MODE_COLUMN);
+}
+
+/**
+ * Iterate over the entire tree (including collapsed sub-elements), probing if any of the elements
+ * has a warning to be displayed.
+ */
+bool outliner_has_element_warnings(const SpaceOutliner &space_outliner)
+{
+  std::function<bool(const ListBase &)> recursive_fn;
+
+  recursive_fn = [&](const ListBase &lb) {
+    LISTBASE_FOREACH (const TreeElement *, te, &lb) {
+      if (te->abstract_element && !te->abstract_element->getWarning().is_empty()) {
+        return true;
+      }
+
+      if (recursive_fn(te->subtree)) {
+        return true;
+      }
+    }
+
+    return false;
+  };
+
+  return recursive_fn(space_outliner.tree);
+}
diff --git a/source/blender/editors/space_outliner/outliner_select.cc b/source/blender/editors/space_outliner/outliner_select.cc
index fd0ee422df0..f7c65bfcff2 100644
--- a/source/blender/editors/space_outliner/outliner_select.cc
+++ b/source/blender/editors/space_outliner/outliner_select.cc
@@ -66,6 +66,7 @@
 #include "RNA_prototypes.h"
 
 #include "outliner_intern.hh"
+#include "tree/tree_display.hh"
 #include "tree/tree_element_seq.hh"
 
 using namespace blender::ed::outliner;
@@ -1557,12 +1558,11 @@ static bool outliner_is_co_within_restrict_columns(const SpaceOutliner *space_ou
 
 bool outliner_is_co_within_mode_column(SpaceOutliner *space_outliner, const float view_mval[2])
 {
-  /* Mode toggles only show in View Layer and Scenes modes. */
-  if (!ELEM(space_outliner->outlinevis, SO_VIEW_LAYER, SO_SCENES)) {
+  if (!outliner_shows_mode_column(*space_outliner)) {
     return false;
   }
 
-  return space_outliner->flag & SO_MODE_COLUMN && view_mval[0] < UI_UNIT_X;
+  return view_mval[0] < UI_UNIT_X;
 }
 
 static bool outliner_is_co_within_active_mode_column(bContext *C,
diff --git a/source/blender/editors/space_outliner/outliner_tree.cc b/source/blender/editors/space_outliner/outliner_tree.cc
index bbd9b48c260..7b3ce499929 100644
--- a/source/blender/editors/space_outliner/outliner_tree.cc
+++ b/source/blender/editors/space_outliner/outliner_tree.cc
@@ -919,10 +919,6 @@ TreeElement *outliner_add_element(SpaceOutliner *space_outliner,
     BLI_assert_msg(false, "Element type should already use new AbstractTreeElement design");
   }
 
-  if (tree_element_warnings_get(te, nullptr, nullptr)) {
-    te->flag |= TE_HAS_WARNING;
-  }
-
   return te;
 }
 
diff --git a/source/blender/editors/space_outliner/tree/tree_display.cc b/source/blender/editors/space_outliner/tree/tree_display.cc
index 141c68594e8..6ab497b3fbb 100644
--- a/source/blender/editors/space_outliner/tree/tree_display.cc
+++ b/source/blender/editors/space_outliner/tree/tree_display.cc
@@ -45,9 +45,9 @@ std::unique_ptr<AbstractTreeDisplay> AbstractTreeDisplay::createFromDisplayMode(
   return nullptr;
 }
 
-bool AbstractTreeDisplay::hasWarnings() const
+bool AbstractTreeDisplay::supportsModeColumn() const
 {
-  return has_warnings;
+  return false;
 }
 
 }  // namespace blender::ed::outliner
diff --git a/source/blender/editors/space_outliner/tree/tree_display.hh b/source/blender/editors/space_outliner/tree/tree_display.hh
index 327f29aa15e..190e35c81d6 100644
--- a/source/blender/editors/space_outliner/tree/tree_display.hh
+++ b/source/blender/editors/space_outliner/tree/tree_display.hh
@@ -75,12 +75,16 @@ class AbstractTreeDisplay {
    */
   virtual ListBase buildTree(const TreeSourceData &source_data) = 0;
 
-  /** Accessor to whether given tree has some warnings to display. */
-  bool hasWarnings() const;
+  /**
+   * Define if the display mode should be allowed to show a mode column on the left. This column
+   * adds an icon to indicate which objects are in the current mode (edit mode, pose mode, etc.)
+   * and allows adding other objects to the mode by clicking the icon.
+   *
+   * Returns false by default.
+   */
+  virtual bool supportsModeColumn() const;
 
  protected:
-  bool has_warnings = false;
-
   /** All derived classes will need a handle to this, so storing it in the base for convenience. */
   SpaceOutliner &space_outliner_;
 };
@@ -100,6 +104,8 @@ class TreeDisplayViewLayer final : public AbstractTreeDisplay {
 
   ListBase buildTree(const TreeSourceData &source_data) override;
 
+  bool supportsModeColumn() const override;
+
  private:
   void add_view_layer(Scene &, ListBase &, TreeElement *);
   void add_layer_collections_recursive(ListBase &, ListBase &, TreeElement &);
@@ -212,6 +218,8 @@ class TreeDisplayScenes final : public AbstractTreeDisplay {
   TreeDisplayScenes(SpaceOutliner &space_outliner);
 
   ListBase buildTree(const TreeSourceData &source_data) override;
+
+  bool supportsModeColumn() const override;
 };
 
 /* -------------------------------------------------------------------- */
diff --git a/source/blender/editors/space_outliner/tree/tree_display_libraries.cc b/source/blender/editors/space_outliner/tree/tree_display_libraries.cc
index 476bbdb63ae..46a89f17687 100644
--- a/source/blender/editors/space_outliner/tree/tree_display_libraries.cc
+++ b/source/blender/editors/space_outliner/tree/tree_display_libraries.cc
@@ -136,9 +136,6 @@ TreeElement *TreeDisplayLibraries::add_library_contents(Main &mainvar, ListBase
           tenlib = outliner_add_element(&space_outliner_, &lb, &mainvar, nullptr, TSE_ID_BASE, 0);
           tenlib->name = IFACE_("Current File");
         }
-        if (tenlib->flag & TE_HAS_WARNING) {
-          has_warnings = true;
-        }
       }
 
       /* Create data-block list parent element on demand. */
diff --git a/source/blender/editors/space_outliner/tree/tree_display_scenes.cc b/source/blender/editors/space_outliner/tree/tree_display_scenes.cc
index 9e00a425a5a..6b1de7f8b95 100644
--- a/source/blender/editors/space_outliner/tree/tree_display_scenes.cc
+++ b/source/blender/editors/space_outliner/tree/tree_display_scenes.cc
@@ -26,6 +26,11 @@ TreeDisplayScenes::TreeDisplayScenes(SpaceOutliner &space_outliner)
 {
 }
 
+bool TreeDisplayScenes::supportsModeColumn() const
+{
+  return true;
+}
+
 ListBase TreeDisplayScenes::buildTree(const TreeSourceData &source_data)
 {
   /* On first view we open scenes. */
diff --git a/source/blender/editors/space_outliner/tree/tree_display_view_layer.cc b/source/blender/editors/space_outliner/tree/tree_display_view_layer.cc
index 19811e45b90..80b3365766a 100644
--- a/source/blender/editors/space_outliner/tree/tree_display_view_layer.cc
+++ b/source/blender/editors/space_outliner/tree/tree_display_view_layer.cc
@@ -55,6 +55,11 @@ TreeDisplayViewLayer::TreeDisplayViewLayer(SpaceOutliner &space_outliner)
 {
 }
 
+bool TreeDisplayViewLayer::supportsModeColumn() const
+{
+  return true;
+}
+
 ListBase TreeDisplayViewLayer::buildTree(const TreeSourceData &source_data)
 {
   ListBase tree = {nullptr};
diff --git a/source/blender/editors/space_outliner/tree/tree_element.cc b/source/blender/editors/space_outliner/tree/tree_element.cc
index 1e3fd2df7c2..94d55b70e3c 100644
--- a/source/blender/editors/space_outliner/tree/tree_element.cc
+++ b/source/blender/editors/space_outliner/tree/tree_element.cc
@@ -100,6 +100,11 @@ std::unique_ptr<AbstractTreeElement> AbstractTreeElement::createFromType(const i
   return nullptr;
 }
 
+StringRefNull AbstractTreeElement::getWarning() const
+{
+  return "";
+}
+
 void AbstractTreeElement::uncollapse_by_default(TreeElement *legacy_te)
 {
   if (!TREESTORE(legacy_te)->used) {
@@ -118,39 +123,4 @@ void tree_element_expand(const AbstractTreeElement &tree_element, SpaceOutliner
   tree_element.expand(space_outliner);
 }
 
-bool tree_element_warnings_get(TreeElement *te, int *r_icon, const char **r_message)
-{
-  TreeStoreElem *tselem = te->store_elem;
-
-  if (tselem->type != TSE_SOME_ID) {
-    return false;
-  }
-  if (te->idcode != ID_LI) {
-    return false;
-  }
-
-  Library *library = (Library *)tselem->id;
-  if (library->tag & LIBRARY_TAG_RESYNC_REQUIRED) {
-    if (r_icon) {
-      *r_icon = ICON_ERROR;
-    }
-    if (r_message) {
-      *r_message = TIP_(
-          "Contains linked library overrides that need to be resynced, updating the library is "
-          "recommended");
-    }
-    return true;
-  }
-  if (library->id.tag & LIB_TAG_MISSING) {
-    if (r_icon) {
-      *r_icon = ICON_ERROR;
-    }
-    if (r_message) {
-      *r_message = TIP_("Missing library");
-    }
-    return true;
-  }
-  return false;
-}
-
 }  // namespace blender::ed::outliner
diff --git a/source/blender/editors/space_outliner/tree/tree_element.hh b/source/blender/editors/space_outliner/tree/tree_element.hh
index c6593a517dd..d665ff49f53 100644
--- a/source/blender/editors/space_outliner/tree/tree_element.hh
+++ b/source/blender/editors/space_outliner/tree/tree_element.hh
@@ -8,6 +8,8 @@
 
 #include <memory>
 
+#include "BLI_string_ref.hh"
+
 struct ListBase;
 struct SpaceOutliner;
 struct TreeElement;
@@ -56,6 +58,12 @@ class AbstractTreeElement {
   }
 
   /**
+   * By letting this return a warning message, the tree element will display a warning icon with
+   * the message in the tooltip.
+   */
+  virtual blender::StringRefNull getWarning() const;
+
+  /**
    * Expand this tree element if it is displayed for the first time (as identified by its
    * tree-store element).
    *
@@ -96,13 +104,4 @@ struct TreeElement *outliner_add_element(SpaceOutliner *space_outliner,
 
 void tree_element_expand(const AbstractTreeElement &tree_element, SpaceOutliner &space_outliner);
 
-/**
- * Get actual warning data of a tree element, if any.
- *
- * \param r_icon: The icon to display as warning.
- * \param r_message: The message to display as warning.
- * \return true if there is a warning, false otherwise.
- */
-bool tree_element_warnings_get(struct TreeElement *te, int *r_icon, const char **r_message);
-
 }  // namespace blender::ed::outliner
diff --git a/source/blender/editors/space_outliner/tree/tree_element_id_library.cc b/source/blender/editors/space_outliner/tree/tree_element_id_library.cc
index 0dcaec0385a..4f1b951ccaf 100644
--- a/source/blender/editors/space_outliner/tree/tree_element_id_library.cc
+++ b/source/blender/editors/space_outliner/tree/tree_element_id_library.cc
@@ -4,6 +4,8 @@
  * \ingroup spoutliner
  */
 
+#include "BLT_translation.h"
+
 #include "DNA_ID.h"
 #include "DNA_listBase.h"
 
@@ -24,4 +26,21 @@ bool TreeElementIDLibrary::isExpandValid() const
   return true;
 }
 
+StringRefNull TreeElementIDLibrary::getWarning() const
+{
+  Library &library = reinterpret_cast<Library &>(id_);
+
+  if (library.tag & LIBRARY_TAG_RESYNC_REQUIRED) {
+    return TIP_(
+        "Contains linked library overrides that need to be resynced, updating the library is "
+        "recommended");
+  }
+
+  if (library.id.tag & LIB_TAG_MISSING) {
+    return TIP_("Missing library");
+  }
+
+  return {};
+}
+
 }  // namespace blender::ed::outliner
diff --git a/source/blender/editors/space_outliner/tree/tree_element_id_library.hh b/source/blender/editors/space_outliner/tree/tree_element_id_library.hh
index ed599cf04da..2d89b55813f 100644
--- a/source/blender/editors/space_outliner/tree/tree_element_id_library.hh
+++ b/source/blender/editors/space_outliner/tree/tree_element_id_library.hh
@@ -17,6 +17,8 @@ class TreeElementIDLibrary final : public TreeElementID {
   TreeElementIDLibrary(TreeElement &legacy_te, Library &library);
 
   bool isExpandValid() const override;
+
+  blender::StringRefNull getWarning() const override;
 };
 
 }  // namespace blender::ed::outliner