Depsgraph: Add utility to stringify recalc flags

Allows to log human-readable list of recalc bits that are set.

The usage is pretty simple:

```
printf("%s: %s %s\n", __func__, id->name, DEG_stringify_recalc_flags(id->recalc).c_str());
```

Pull Request: https://projects.blender.org/blender/blender/pulls/137715

source/blender/depsgraph/DEG_depsgraph_debug.hh

@@ -11,6 +11,7 @@
 #pragma once
 
 #include <cstdio>
+#include <string>
 
 #include "BLI_string_ref.hh"
 
@@ -65,3 +66,13 @@ bool DEG_debug_graph_relations_validate(Depsgraph *graph,
 
 /** Perform consistency check on the graph. */
 bool DEG_debug_consistency_check(Depsgraph *graph);
+
+/** Convert bitflag representation of recalculation flags to string that consists of human-readable
+ * names of recalculation bits that are set in the given mask.
+ *
+ * If flags == 0 the result is "NONE".
+ *
+ * Example:
+ *   DEG_stringify_recalc_flags(ID_RECALC_GEOMETRY | ID_RECALC_SHADING) -> "GEOMETRY, SHADING".
+ */
+std::string DEG_stringify_recalc_flags(unsigned int flags);

source/blender/depsgraph/intern/depsgraph_debug.cc

@@ -24,6 +24,8 @@
 #include "intern/node/deg_node_id.hh"
 #include "intern/node/deg_node_time.hh"
 
+#include "BLI_math_bits.h"
+
 namespace deg = blender::deg;
 
 void DEG_debug_flags_set(Depsgraph *depsgraph, int flags)
@@ -357,3 +359,36 @@ void DEG_debug_print_eval_time(Depsgraph *depsgraph,
           time);
   fflush(stdout);
 }
+
+static std::string stringify_append_bit(const std::string &str, IDRecalcFlag tag)
+{
+  const char *tag_name = DEG_update_tag_as_string(tag);
+  if (tag_name == nullptr) {
+    return str;
+  }
+  std::string result = str;
+  if (!result.empty()) {
+    result += ", ";
+  }
+  result += tag_name;
+  return result;
+}
+
+std::string DEG_stringify_recalc_flags(uint flags)
+{
+  if (flags == 0) {
+    return "NONE";
+  }
+  std::string result;
+  uint current_flag = flags;
+  /* Special cases to avoid ALL flags from being split into individual bits. */
+  if ((current_flag & ID_RECALC_PSYS_ALL) == ID_RECALC_PSYS_ALL) {
+    result = stringify_append_bit(result, ID_RECALC_PSYS_ALL);
+  }
+  /* Handle all the rest of the flags. */
+  while (current_flag != 0) {
+    IDRecalcFlag tag = (IDRecalcFlag)(1 << bitscan_forward_clear_uint(&current_flag));
+    result = stringify_append_bit(result, tag);
+  }
+  return result;
+}

source/blender/depsgraph/intern/depsgraph_tag.cc

@@ -401,38 +401,12 @@ void graph_id_tag_update_single_flag(Main *bmain,
   deg_graph_id_tag_legacy_compat(bmain, graph, id, tag, update_source);
 }
 
-std::string stringify_append_bit(const std::string &str, IDRecalcFlag tag)
-{
-  const char *tag_name = DEG_update_tag_as_string(tag);
-  if (tag_name == nullptr) {
-    return str;
-  }
-  std::string result = str;
-  if (!result.empty()) {
-    result += ", ";
-  }
-  result += tag_name;
-  return result;
-}
-
 std::string stringify_update_bitfield(uint flags)
 {
   if (flags == 0) {
     return "LEGACY_0";
   }
-  std::string result;
-  uint current_flag = flags;
-  /* Special cases to avoid ALL flags form being split into
-   * individual bits. */
-  if ((current_flag & ID_RECALC_PSYS_ALL) == ID_RECALC_PSYS_ALL) {
-    result = stringify_append_bit(result, ID_RECALC_PSYS_ALL);
-  }
-  /* Handle all the rest of the flags. */
-  while (current_flag != 0) {
-    IDRecalcFlag tag = (IDRecalcFlag)(1 << bitscan_forward_clear_uint(&current_flag));
-    result = stringify_append_bit(result, tag);
-  }
-  return result;
+  return DEG_stringify_recalc_flags(flags);
 }
 
 const char *update_source_as_string(eUpdateSource source)