AstarPath.cs ScanLoop

//public void ScanLoop (OnScanStatus statusCallback) {
    public IEnumerable<Progress> ScanLoop() {
        if (graphs == null) {
            yield break;
        }

        isScanning = true;
        euclideanEmbedding.dirty = false;

        VerifyIntegrity ();

        BlockUntilPathQueueBlocked ();

        if (!Application.isPlaying) {
            GraphModifier.FindAllModifiers ();
            RelevantGraphSurface.FindAllGraphSurfaces ();
        }

        RelevantGraphSurface.UpdateAllPositions ();

        astarData.UpdateShortcuts ();

        //if (statusCallback != null) statusCallback (new Progress (0.05F,"Pre processing graphs"));
        yield return new Progress(0.05F, "Pre processing graphs");

        if (OnPreScan != null) {
            OnPreScan (this);
        }

        GraphModifier.TriggerEvent (GraphModifier.EventType.PreScan);

        System.DateTime startTime = System.DateTime.UtcNow;

        // Destroy previous nodes
        for (int i=0;i<graphs.Length;i++) {
            if (graphs[i] != null) {
                graphs[i].GetNodes (delegate (GraphNode node) {
                    node.Destroy ();
                    return true;
                });
            }
        }

        for (int i=0;i<graphs.Length;i++) {

            NavGraph graph = graphs[i];

            if (graph == null) {
                //if (statusCallback != null) statusCallback (new Progress (AstarMath.MapTo (0.05F,0.7F,(float)(i+0.5F)/(graphs.Length+1)),"Skipping graph "+(i+1)+" of "+graphs.Length+" because it is null"));
                yield return new Progress(AstarMath.MapTo(0.05F, 0.7F, (float)(i + 0.5F) / (graphs.Length + 1)), "Skipping graph " + (i + 1) + " of " + graphs.Length + " because it is null");
                continue;
            }

            if (OnGraphPreScan != null) {
                //if (statusCallback != null) statusCallback (new Progress (AstarMath.MapToRange (0.1F,0.7F,(float)(i)/(graphs.Length)),"Scanning graph "+(i+1)+" of "+graphs.Length+" - Pre processing"));
                yield return new Progress(Mathf.Lerp(0.1F, 0.7F, (float)(i) / (graphs.Length)), "Scanning graph " + (i + 1) + " of " + graphs.Length + " - Pre processing");
                OnGraphPreScan (graph);
            }

            //float minp = AstarMath.MapToRange (0.1F,0.7F,(float)(i)/(graphs.Length));
            //float maxp = AstarMath.MapToRange (0.1F,0.7F,(float)(i+0.95F)/(graphs.Length));

            //if (statusCallback != null) statusCallback (new Progress (minp,"Scanning graph "+(i+1)+" of "+graphs.Length));

            // Just used for progress information
            // This graph will advance the progress bar from minp to maxp
            float minp = Mathf.Lerp(0.1F, 0.7F, (float)(i) / (graphs.Length));
            float maxp = Mathf.Lerp(0.1F, 0.7F, (float)(i + 0.95F) / (graphs.Length));

            var progressDescriptionPrefix = "Scanning graph " + (i + 1) + " of " + graphs.Length;

            yield return new Progress(minp, progressDescriptionPrefix);


            //OnScanStatus info = null;
            //if (statusCallback != null) {
            //  info = delegate (Progress p) {
            //      p.progress = AstarMath.MapToRange (minp, maxp, p.progress);
            //      statusCallback (p);
            //  };
            //}
            foreach (var p in graph.ScanInternal())
            {
                yield return new Progress(AstarMath.MapToRange(minp, maxp, p.progress), progressDescriptionPrefix + " - " + p.description);
            }

            //graph.ScanInternal (info);

            // Assign the graph index to every node in the graph
            graph.GetNodes (delegate (GraphNode node) {
                node.GraphIndex = (uint)i;
                return true;
            });

            if (OnGraphPostScan != null) {
                //if (statusCallback != null) statusCallback (new Progress (AstarMath.MapToRange (0.1F,0.7F,(float)(i+0.95F)/(graphs.Length)),"Scanning graph "+(i+1)+" of "+graphs.Length+" - Post processing"));
                yield return new Progress(AstarMath.MapToRange(0.1F, 0.7F, (float)(i + 0.95F) / (graphs.Length)), progressDescriptionPrefix + " - Post processing");
                OnGraphPostScan (graph);
            }
        }

        //if (statusCallback != null) statusCallback (new Progress (0.8F,"Post processing graphs"));
        yield return new Progress(0.8F, "Post processing graphs");

        if (OnPostScan != null) {
            OnPostScan (this);
        }
        GraphModifier.TriggerEvent (GraphModifier.EventType.PostScan);

        try {
            FlushWorkItems(false, true);
        } catch (System.Exception e) {
            Debug.LogException (e);
        }

        isScanning = false;

        //if (statusCallback != null) statusCallback (new Progress (0.90F,"Computing areas"));
        yield return new Progress(0.90F, "Computing areas");

        FloodFill ();

        VerifyIntegrity ();

        //if (statusCallback != null) statusCallback (new Progress (0.95F,"Late post processing"));
        yield return new Progress(0.95F, "Late post processing");

        // Signal that we have stopped scanning here
        // Note that no yields can happen after this point
        // since then other parts of the system can start to interfere
        isScanning = false;

        if (OnLatePostScan != null) {
            OnLatePostScan (this);
        }
        GraphModifier.TriggerEvent (GraphModifier.EventType.LatePostScan);

        euclideanEmbedding.dirty = true;
        euclideanEmbedding.RecalculatePivots ();

        //Perform any blocking actions and unblock (probably, some tasks might take a few frames)
        PerformBlockingActions(true);

        lastScanTime = (float)(System.DateTime.UtcNow-startTime).TotalSeconds;

        System.GC.Collect ();

        AstarLog ("Scanning - Process took "+(lastScanTime*1000).ToString ("0")+" ms to complete");
    }