Add wxComboBox::Popup() and Dismiss() to manually show or hide its popup.

Add implementations for wxMSW and wxGTK.

Closes #11506.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63242 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/combobox.cpp

@@ -702,6 +702,22 @@ void wxComboBox::OnUpdateSelectAll(wxUpdateUIEvent& event)
     event.Enable(IsEditable() && !wxTextEntry::IsEmpty());
 }
 
+void wxComboBox::MSWDoPopupOrDismiss(bool show)
+{
+    wxASSERT_MSG( !HasFlag(wxCB_SIMPLE),
+                  wxT("can't popup/dismiss the list for simple combo box") );
+
+    // we *must* set focus to the combobox before showing or hiding the drop
+    // down as without this we get WM_LBUTTONDOWN messages with invalid HWND
+    // when hiding it (whether programmatically or manually) resulting in a
+    // crash when we pass them to IsDialogMessage()
+    //
+    // this can be seen in the combo page of the widgets sample under Windows 7
+    SetFocus();
+
+    ::SendMessage(GetHwnd(), CB_SHOWDROPDOWN, show, 0);
+}
+
 #if wxUSE_TOOLTIPS
 
 void wxComboBox::DoSetToolTip(wxToolTip *tip)