fix(gui): keyboard shortcuts cleanup after #15706 (#15862)

src/slic3r/GUI/KeyChord.cpp

@@ -182,6 +182,16 @@ bool KeyChord::is_menu_accelerator() const
     return valid() && ((modifiers & (wxMOD_CONTROL | wxMOD_ALT | wxMOD_RAW_CONTROL)) != 0 || (!is_printable(key) && key != WXK_SPACE));
 }
 
+// Only a chord the desktop acts on while still delivering it to the app belongs here.
+bool KeyChord::is_system_shortcut() const
+{
+#ifdef _WIN32
+    return modifiers == wxMOD_ALT && (key == WXK_F4 || key == WXK_SPACE);
+#else
+    return false;
+#endif
+}
+
 std::string KeyChord::to_string() const
 {
     if (!valid())