Cancellation option is added to Triangulate, Refine and Smooth methods

[YasarYY]

Triangulation operations are now cancellable. This option comes handy for time-consuming operations. Option added to Triangulate and Refine methods with quality parameter, and to Smooth method.

If no cancellation token is given, which is default, these methods works uncancellable and synchronous.

I didn't implement this functionality to Viewer UI in order not to complicate it. Viewer works the same synchronous way.

A usage example snippet:

// in class:
TriangleNet.Mesh netMesh;
CancellationTokenSource cancellationTokenSource;

// in an async method:
cancellationTokenSource = new CancellationTokenSource();
try
{
	await Task.Run(() => {
		netMesh = (TriangleNet.Mesh)polygon.Triangulate(constraintOptions, qualityOptions, cancellationTokenSource.Token);
		smoother.Smooth(netMesh, 20, 0.01, cancellationTokenSource.Token);
	});
}
catch (OperationCanceledException)
{
	// triangulation is canceled
}
catch (Exception ex)
{
	// some other exception
}

// cancellation method:
public void CancelOperation()
{
	cancellationTokenSource.Cancel();
}

[wo80]

Thanks @YasarYY , cancellation support is a welcome addition!

Please remove the Windows specific projects from the solution file. This should make the tests run successfully.

[wo80]

I didn't implement this functionality to Viewer UI in order not to complicate it.

That's okay. I will look at those projects myself and update the code, if necessary.

[YasarYY]

Hi Christian,
I removed the Windows specific projects from the solution file.

[wo80]

Alright, this looks good.

Do you plan to add cancellation support to the actual triangulation algorithms or is this ready to merge? I wouldn't mind merging the PR the way it is.

[YasarYY]

I don't intend to make any further implementation, unless it is necessary for some reason. Usage of ThrowIfCancellationRequested() at lower levels may degrade performance. I used CPU profiling in an attempt to find optimal places to call ThrowIfCancellationRequested().

With current implementation, ThrowIfCancellationRequested() is called by EnforceQuality() (which is called by Triangulate() and Refine()) and by Smooth(). At my trials, I got cancellation responses below 1 second on a relatively slow machine.

So, in my opinion this is ready to merge. 😌

[wo80]

Thanks again for your contribution!