// Dequeue the next file, load it as a BitmapImage, and return it. If there is no file, store the callback and dispatcher, to be called when the next file is enqueued.
// If a file is under review, it will NOT be passed to the next module; it will silently exit the workflow.
public ImageSource NextImage(NextImageCallback callback, System.Windows.Threading.Dispatcher dispatcher)
{
// TODO Consider reusing the dispatcher from BasicModule, which was added as part of logging.
ImageSource returnValue = null;
bool gotLock = false;
while (!gotLock)
{
fileLock.Enter(ref gotLock);
}
// We have the lock.
// Clear any saved callbacks; this request overrides them.
nextImageCallback = null;
nextImageCallbackDispatcher = null;
if (files.Count > 0)
{
// Great! We can dequeue.
FileInfo file;
// Get the next file to process.
file = files.Dequeue();
log($"ImageReviewer.NextImage: Dequeued file: {file.FullName}");
// Save the file so we have it when the decision to accept/reject comes back.
fileUnderReview = file;
fileLock.Exit();
// Load the image, AFTER exiting.
try
{
returnValue = makeImage(file);
}
catch (Exception e)
{
log($"ImageReviewer.NextImage: makeImage threw exception: {e.Message}");
log("ImageReviewer.NextImage: Ignoring this image and recursing.");
returnValue = NextImage(callback, dispatcher);
}
}
else
{
// Nothing to dequeue. Save a callback.
nextImageCallback = callback;
nextImageCallbackDispatcher = dispatcher;
fileLock.Exit();
// And clear the current saved file.
fileUnderReview = null;
log($"ImageReviewer.NextImage: Nothing to dequeue. Saved callback.");
}
return(returnValue);
}
private void enqueue(FileInfo file)
{
bool gotLock = false;
while (!gotLock)
{
fileLock.Enter(ref gotLock);
}
// We have the lock.
files.Enqueue(file);
if (nextImageCallback != null)
{
// Someone's waiting. Hand the image straight to them.
// First, let's take care of the work that must be locked.
// We'll save a copy of the callback and clear the shared memory.
NextImageCallback callback = nextImageCallback;
Dispatcher dispatcher = nextImageCallbackDispatcher;
nextImageCallback = null;
nextImageCallbackDispatcher = null;
// Save the file since it's being reviewed.
fileUnderReview = file;
fileLock.Exit();
log($"ImageReviewer.enqueue: Enqueued and invoking callback for: {file.FullName}");
// Now we do the real work: make a new BitmapImage and pass it on.
dispatcher.Invoke(() => callback());
}
else
{
// We're just enqueueing in the background. Nothing more to do.
fileLock.Exit();
log($"ImageReviewer.enqueue: Enqueued: {file.FullName}");
}
}
