/// <summary>
/// Found on Google Groups when searching for "Region.Union" while looking
/// for bugs:
/// ---
/// Hello,
///
/// I did not run your code, but I know Region.Union is flawed in both 1.0 and
/// 1.1, so I assume it is in the gdi+ unmanged code dll. The best workaround,
/// in terms of speed, is to use a PdnGraphicsPath, but it must be a path with
/// FillMode = FillMode.Winding. You add the rectangles to the path, then you do
/// union onto an empty region with the path. The important point is to do only
/// one union call on a given empty region. We created a "super region" object
/// to hide all these bugs and optimize clipping operations. In fact, it is much
/// faster to use the path than to call Region.Union for each rectangle.
///
/// Too bad about Region.Union. A lot of people will hit this bug, as it is
/// essential in high-performance animation.
///
/// Regards,
/// Frank Hileman
/// Prodige Software Corporation
/// ---
/// </summary>
/// <param name="rectsF"></param>
/// <param name="startIndex"></param>
/// <param name="length"></param>
/// <returns></returns>
public static PdnRegion RectanglesToRegion(RectangleF[] rectsF, int startIndex, int length)
{
PdnRegion region;
if (rectsF == null || rectsF.Length == 0 || length == 0)
{
region = PdnRegion.CreateEmpty();
}
else
{
using (PdnGraphicsPath path = new PdnGraphicsPath())
{
path.FillMode = FillMode.Winding;
if (startIndex == 0 && length == rectsF.Length)
{
path.AddRectangles(rectsF);
}
else
{
for (int i = startIndex; i < startIndex + length; ++i)
{
path.AddRectangle(rectsF[i]);
}
}
region = new PdnRegion(path);
}
}
return region;
}