protected override Task HandleMouseDownAsync(MapViewMouseButtonEventArgs e)
{
//Select a line feature and place the initial graphic. Clear out any
//previously placed graphic
return(QueuedTask.Run(() => {
var mapPoint = this.ActiveMapView.ClientToMap(e.ClientPoint);
var lineFeature = Module1.SelectLineFeature(mapPoint);
if (lineFeature != null)
{
var nearest = GeometryEngine.NearestPoint(lineFeature, mapPoint);
lock (_lock) {
_workingLocation = null;
_lineFeature = lineFeature;
if (_graphic != null)
{
_graphic.Dispose();
}
_graphic = this.AddOverlay(nearest.Point, _pointSymbol.MakeSymbolReference());
_trackingMouseMove = TrackingState.CanTrack;
}
}
else
{
lock (_lock) {
_workingLocation = null;
_lineFeature = null;
if (_graphic != null)
{
_graphic.Dispose();
}
_graphic = null;
_trackingMouseMove = TrackingState.NotTracking;
}
}
}));
}
protected override async void OnToolMouseMove(MapViewMouseEventArgs e)
{
//All of this logic is to avoid unnecessarily updating the graphic position
//for ~every~ mouse move. We skip any "intermediate" points in-between rapid
//mouse moves.
lock (_lock) {
if (_trackingMouseMove == TrackingState.NotTracking)
{
return;
}
else
{
if (_workingLocation.HasValue)
{
_lastLocation = e.ClientPoint;
return;
}
else
{
_lastLocation = e.ClientPoint;
_workingLocation = e.ClientPoint;
}
}
_trackingMouseMove = TrackingState.Tracking;
}
//The code "inside" the QTR will execute for all points that
//get "buffered" or "queued". This avoids having to spin up a QTR
//for ~every~ point of ~every mouse move.
await QueuedTask.Run(() => {
var symReference = _pointSymbol.MakeSymbolReference();
while (true)
{
System.Windows.Point?point;
Polyline lineFeature = null;
IDisposable graphic = null;
lock (_lock) {
point = _lastLocation;
_lastLocation = null;
_workingLocation = point;
if (point == null || !point.HasValue) //No new points came in while we updated the overlay
{
_workingLocation = null;
break;
}
else if (_lineFeature == null || _graphic == null) //conflict with the mouse down,
//If this happens then we are done. A new line and point will be
//forthcoming from the SketchCompleted callback
{
_trackingMouseMove = TrackingState.NotTracking;
break;
}
lineFeature = _lineFeature;
graphic = _graphic;
}
//update the graphic overlay
var nearest = GeometryEngine.NearestPoint(lineFeature, MapView.Active.ClientToMap(point.Value));
this.UpdateOverlay(graphic, nearest.Point, symReference);
}
});
}