[DllImport("uxtheme.dll", SetLastError = true)]
public static extern HRESULT GetThemeTextExtent(
IntPtr hTheme,
HDC hdc,
int iPartId,
int iStateId,
[MarshalAs(UnmanagedType.LPWStr)] string pszText,
int cchCharCount,
uint dwTextFlags,
ref RECT pBoundingRect,
out RECT pExtentRect
);