Compositor: Export operation results as debug option

When fixing issues, seeing operation results can be helpful for
detecting which operation went wrong.

This commit adds an option for exporting all operations results to
image files.
Exceptions are:
- Output operations: They are already exported or can be seen in UI.
- Constant operations: There are too many and is rarely useful.

They are exported to "<temp session folder>/COM_operations/"
with filenames "<operation class name>_<operation id>.png".
Only works on full frame execution mode.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D11722

source/blender/compositor/intern/COM_Debug.h

@@ -30,6 +30,9 @@ namespace blender::compositor {
 static constexpr bool COM_EXPORT_GRAPHVIZ = false;
 static constexpr bool COM_GRAPHVIZ_SHOW_NODE_NAME = false;
 
+/* Saves operations results to image files. */
+static constexpr bool COM_EXPORT_OPERATION_BUFFERS = false;
+
 class Node;
 class ExecutionSystem;
 class ExecutionGroup;
@@ -75,6 +78,9 @@ class DebugInfo {
         m_group_states[execution_group] = EG_WAIT;
       }
     }
+    if (COM_EXPORT_OPERATION_BUFFERS) {
+      delete_operation_exports();
+    }
   };
 
   static void node_added(const Node *node)
@@ -118,6 +124,14 @@ class DebugInfo {
     }
   };
 
+  static void operation_rendered(const NodeOperation *op, MemoryBuffer *render)
+  {
+    /* Don't export constant operations as there are too many and it's rarely useful. */
+    if (COM_EXPORT_OPERATION_BUFFERS && render && !render->is_a_single_elem()) {
+      export_operation(op, render);
+    }
+  }
+
   static void graphviz(const ExecutionSystem *system, StringRefNull name = "");
 
  protected:
@@ -133,6 +147,9 @@ class DebugInfo {
       const char *name, const char *color, const char *style, char *str, int maxlen);
   static int graphviz_legend(char *str, int maxlen, bool has_execution_groups);
   static bool graphviz_system(const ExecutionSystem *system, char *str, int maxlen);
+
+  static void export_operation(const NodeOperation *op, MemoryBuffer *render);
+  static void delete_operation_exports();
 };
 
 }  // namespace blender::compositor