Fix: Nodes: memory leak in extra info tooltips

The issue was that the tooltip function arguments were sometimes allocated but
not freed. The solution is to handle the lifetime of the argument better. The
code now makes a copy of the argument when it's passed to a layout function. In
an idea world, one could just use something like `std::function` instead of
manual memory management, but the API does not support it yet.

This was caused by f3a1d8fad5.

Pull Request: https://projects.blender.org/blender/blender/pulls/143043

source/blender/editors/space_node/node_draw.cc

@@ -154,6 +154,18 @@ struct TreeDrawContext {
    * during drawing. The array is indexed by `bNode::index()`.
    */
   Array<Vector<NodeExtraInfoRow>> extra_info_rows_per_node;
+
+  ~TreeDrawContext()
+  {
+    for (MutableSpan<NodeExtraInfoRow> rows : this->extra_info_rows_per_node) {
+      for (NodeExtraInfoRow &row : rows) {
+        if (row.tooltip_fn_free_arg) {
+          BLI_assert(row.tooltip_fn_copy_arg);
+          row.tooltip_fn_free_arg(row.tooltip_fn_arg);
+        }
+      }
+    }
+  }
 };
 
 float grid_size_get()
@@ -2321,6 +2333,9 @@ static NodeExtraInfoRow row_from_used_named_attribute(
   row.tooltip_fn = named_attribute_tooltip;
   row.tooltip_fn_arg = new NamedAttributeTooltipArg{usage_by_attribute_name};
   row.tooltip_fn_free_arg = [](void *arg) { delete static_cast<NamedAttributeTooltipArg *>(arg); };
+  row.tooltip_fn_copy_arg = [](void *arg) -> void * {
+    return new NamedAttributeTooltipArg(*static_cast<NamedAttributeTooltipArg *>(arg));
+  };
   return row;
 }
 
@@ -2469,6 +2484,12 @@ static void node_draw_extra_info_row(const bNode &node,
   const float but_icon_width = NODE_HEADER_ICON_SIZE * 0.8f;
   const float but_icon_right = but_icon_left + but_icon_width;
 
+  void *tooltip_arg = extra_info_row.tooltip_fn_arg;
+  if (tooltip_arg && extra_info_row.tooltip_fn_free_arg) {
+    BLI_assert(extra_info_row.tooltip_fn_copy_arg);
+    tooltip_arg = extra_info_row.tooltip_fn_copy_arg(tooltip_arg);
+  }
+
   UI_block_emboss_set(&block, ui::EmbossType::None);
   uiBut *but_icon = uiDefIconBut(&block,
                                  ButType::But,
@@ -2483,10 +2504,8 @@ static void node_draw_extra_info_row(const bNode &node,
                                  0,
                                  extra_info_row.tooltip);
   if (extra_info_row.tooltip_fn != nullptr) {
-    UI_but_func_tooltip_set(but_icon,
-                            extra_info_row.tooltip_fn,
-                            extra_info_row.tooltip_fn_arg,
-                            extra_info_row.tooltip_fn_free_arg);
+    UI_but_func_tooltip_set(
+        but_icon, extra_info_row.tooltip_fn, tooltip_arg, extra_info_row.tooltip_fn_free_arg);
   }
   UI_block_emboss_set(&block, ui::EmbossType::Emboss);
 
@@ -2509,8 +2528,7 @@ static void node_draw_extra_info_row(const bNode &node,
 
   if (extra_info_row.tooltip_fn != nullptr) {
     /* Don't pass tooltip free function because it's already used on the uiBut above. */
-    UI_but_func_tooltip_set(
-        but_text, extra_info_row.tooltip_fn, extra_info_row.tooltip_fn_arg, nullptr);
+    UI_but_func_tooltip_set(but_text, extra_info_row.tooltip_fn, tooltip_arg, nullptr);
   }
 
   if (node.is_muted()) {

source/blender/nodes/NOD_node_extra_info.hh

@@ -18,6 +18,7 @@ struct NodeExtraInfoRow {
   uiButToolTipFunc tooltip_fn = nullptr;
   void *tooltip_fn_arg = nullptr;
   void (*tooltip_fn_free_arg)(void *) = nullptr;
+  void *(*tooltip_fn_copy_arg)(void *) = nullptr;
 };
 
 struct NodeExtraInfoParams {