allow using wxBG_STYLE_CUSTOM even with the native controls and use it in wxTreeCtrl (see #9832)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58380 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -734,6 +734,10 @@ bool wxTreeCtrl::Create(wxWindow *parent,
     if ( !MSWCreateControl(WC_TREEVIEW, wstyle, pos, size) )
         return false;
 
+    // this significantly reduces flicker when refreshing the control, for some
+    // reason the native control itself doesn't avoid background repainting
+    SetBackgroundStyle(wxBG_STYLE_CUSTOM);
+
 #if wxUSE_COMCTL32_SAFELY
     wxWindow::SetBackgroundColour(wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW));
     wxWindow::SetForegroundColour(wxWindow::GetParent()->GetForegroundColour());