2 files changed, 17 insertions, 1 deletions
diff --git a/app/win/window_impl.cc b/app/win/window_impl.cc
index b28eab5..8ddd2bc 100644
--- a/app/win/window_impl.cc
+++ b/app/win/window_impl.cc
@@ -180,7 +180,15 @@ LRESULT CALLBACK WindowImpl::WndProc(HWND hwnd,
   if (!window)
     return 0;
 
-  return window->OnWndProc(message, w_param, l_param);
+  LRESULT return_code = window->OnWndProc(message, w_param, l_param);
+
+  // Clean up state.  Do this after the above call so subclasses still have a
+  // valid hwnd().  Can't wait until WM_NCDESTROY because by then |hwnd| is not
+  // guaranteed to be reported to us.
+  if (message == WM_DESTROY)
+    window->OnDestroy();
+
+  return return_code;
 }
 
 std::wstring WindowImpl::GetWindowClassName() {
@@ -211,4 +219,8 @@ std::wstring WindowImpl::GetWindowClassName() {
   return name;
 }
 
+void WindowImpl::OnDestroy() {
+  hwnd_ = 0;
+}
+
 }  // namespace app
diff --git a/app/win/window_impl.h b/app/win/window_impl.h
index fb5d512..dd7ef5a 100644
--- a/app/win/window_impl.h
+++ b/app/win/window_impl.h
@@ -87,6 +87,10 @@ class WindowImpl : public MessageMapInterface {
   // If necessary, this registers the window class.
   std::wstring GetWindowClassName();
 
+  // Called when the HWND gets a WM_DESTROY message; should cause us to clean
+  // up any state.
+  void OnDestroy();
+
   // All classes registered by WidgetWin start with this name.
   static const wchar_t* const kBaseClassName;