GetDesktopResolution() during Setup()?

The following doesn’t work because SDL is not initialised yet by this stage.

[code]void InGameEditorApplication::Setup()
{
IntVector2 desktopResolution = GetSubsystem()->GetDesktopResolution();

engineParameters_["WindowWidth"] = desktopResolution.x_;
engineParameters_["WindowHeight"] = desktopResolution.y_;

}[/code]

What other options do I have? How does the editor make the window the correct size for that matter?