public override void OnPreviewGUI(Rect r, GUIStyle background)
{
base.OnPreviewGUI(r, background);
if (ShowIsGenerating(base.target as ProceduralMaterial) && (r.width > 50f))
{
EditorGUI.DropShadowLabel(new Rect(r.x, r.y, r.width, 20f), "Generating...");
}
}