// perform union on currently selected layer
private void unionButton_Click(object sender, EventArgs e)
{
toolBuilder.addHeader("Union");
// textbox for new layername
TextBox textbox = toolBuilder.addTextboxWithCaption("New layername:");
Label errorLabel = toolBuilder.addErrorLabel();
Button button = toolBuilder.addButton("Union", (Layer l) =>
{
// user has not set new layername
if (textbox.Text.Length == 0)
{
toolBuilder.setError("Provide name");
return;
}
// create temporary layer
Layer copyLayer = new Layer(l.Name);
copyLayer.Boundingbox = new Envelope(l.Boundingbox);
copyLayer.createQuadTree();
// copy all features to temp layer
foreach (Feature f in l.Features.Values)
copyLayer.addFeature(new Feature((IGeometry)f.Geometry.Clone(), f.ID));
// create new layer with same boundingbox
Layer newLayer = new Layer(textbox.Text);
newLayer.Boundingbox = new Envelope(l.Boundingbox);
newLayer.createQuadTree();
// init progress bar
int numFeatures = copyLayer.Features.Values.Count;
progressLabel.Text = "Performing union";
progressBar.Minimum = 0;
progressBar.Maximum = numFeatures;
BackgroundWorker bw = new BackgroundWorker();
bw.WorkerReportsProgress = true;
// perform merge in another thread
bw.DoWork += (object wsender, DoWorkEventArgs we) =>
{
// threadsafe list of merged features
ConcurrentBag<Feature> newFeatures = new ConcurrentBag<Feature>();
var finished = new CountdownEvent(1);
Object _lock = new object();
// create thread function
var merge = new WaitCallback((state) =>
{
Random rnd = new Random();
while (true)
{
Feature f;
lock (_lock)
{
// break if no more features
if (copyLayer.Features.Count == 0)
break;
// get random index
int index = rnd.Next(copyLayer.Features.Count);
// get corresponding random feature
f = copyLayer.Features[copyLayer.Features.Keys.ToList()[index]];
// remove feature from layer
copyLayer.delFeature(f);
}
f.ID = -1;
while (true)
{
List<Feature> intersects;
// aquire lock to avoid race conditions
lock (_lock)
{
// get all features intersecting feature
intersects = copyLayer.getWithin(f.Geometry);
// remove features from layer
foreach (Feature intersect in intersects)
copyLayer.delFeature(intersect);
}
// if no intersects, no merging is necessary
if (intersects.Count == 0)
break;
// merge all features
foreach (Feature intersect in intersects)
{
f = new Feature(f.Geometry.Union(intersect.Geometry));
bw.ReportProgress(1);
}
}
// add feature to list of new features
newFeatures.Add(f);
}
finished.Signal();
});
// spawn eight threads, this is not always optimal but a good approximation
for (int i = 0; i < 8; i++)
{
finished.AddCount();
ThreadPool.QueueUserWorkItem(merge);
}
finished.Signal();
finished.Wait();
bw.ReportProgress(-newFeatures.Count);
// add all merged features back to temp layer
foreach (Feature f in newFeatures)
copyLayer.addFeature(f);
newFeatures = new ConcurrentBag<Feature>();
finished = new CountdownEvent(1);
// perform a final single threaded merge
merge(false);
// add all final merged features to new layer
foreach (Feature f in newFeatures)
newLayer.addFeature(f);
};
bw.RunWorkerCompleted += (object wsender, RunWorkerCompletedEventArgs we) =>
{
// reset progress bar
progressBar.Value = 0;
progressLabel.Text = "";
// insert new layer and redraw map
Layers.Insert(0, newLayer);
redraw();
};
bw.ProgressChanged += (object wsender, ProgressChangedEventArgs we) =>
{
// update progress bar
if (we.ProgressPercentage < 0)
{
progressBar.Value = 0;
progressBar.Maximum = -we.ProgressPercentage;
progressLabel.Text = "Union - Second pass";
}
else
progressBar.Value += we.ProgressPercentage;
};
bw.RunWorkerAsync();
});
// reset default new layer name when selected layer is changed
toolBuilder.resetAction = (Layer l) => {
textbox.Text = (l == null) ? "" : l.Name + "_union";
};
toolBuilder.reset();
}
