Support of composite editors for comboboxes

platform/platform-impl/src/com/intellij/ide/ui/laf/darcula/ui/DarculaComboBoxUI.java

@@ -17,6 +17,7 @@ package com.intellij.ide.ui.laf.darcula.ui;
 
 import com.intellij.ide.ui.laf.darcula.DarculaUIUtil;
 import com.intellij.openapi.ui.GraphicsConfig;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.ui.Gray;
 import com.intellij.ui.JBColor;
 import com.intellij.util.ui.JBInsets;
@@ -419,4 +420,18 @@ public class DarculaComboBoxUI extends BasicComboBoxUI implements Border {
   public boolean isBorderOpaque() {
     return false;
   }
+
+  @Override
+  protected void configureEditor() {
+    super.configureEditor();
+    if (Registry.is("ide.ui.composite.editor.for.combobox")) {
+      // BasicComboboxUI sets focusability depending on the combobox focusability.
+      // JPanel usually is unfocusable and uneditable.
+      // It could be set as an editor when people want to have a composite component as an editor.
+      // In such cases we should restore unfocusable state for panels.
+      if (editor instanceof JPanel) {
+        editor.setFocusable(false);
+      }
+    }
+  }
 }

platform/util/resources/misc/registry.properties

@@ -857,4 +857,5 @@ low.memory.watcher.sync.description=Whether LowMemoryWatcher runnables should be
 typing.freeze.report.dumps=false
 typing.freeze.report.dumps.description=Automatically reports thread dumps to our statistics server
 
-store.basedir.parent.detection=true
+store.basedir.parent.detection=true
+ide.ui.composite.editor.for.combobox=false