controller | Complete , fast and testable actions for Rack and Hanami | Model View Controller library

The long execution time comes from the fact that each child of a Parent registers a listener with the disabled and treeVisible properties of that Parent. The way JavaFX is currently implemented, these listeners are stored in an array (i.e. a list structure). Adding the listeners is relatively low cost because the new listener is simply inserted at the end of the array, with an occasional resize of the array. However, when you remove a child from its Parent and the listeners are removed, the array needs to be linearly searched so that the correct listener is found and removed. This happens for each removed child individually.

So, when you clear the children list of the Group you are triggering 1,000,000 linear searches for both properties, resulting in a total of 2,000,000 linear searches. And to make things worse, the listener to be removed is either--depending on the order the children are removed--always at the end of the array, in which case there's 2,000,000 worst case linear searches, or always at the start of the array, in which case there's 2,000,000 best case linear searches, but where each individual removal results in all remaining elements having to be shifted over by one.

There are at least two solutions/workarounds:

1. Don't display 1,000,000 nodes. If you can, try to only display nodes for the data that can actually be seen by the user. For example, the virtualized controls such as ListView and TableView only display about 1-20 cells at any given time.

2. Don't clear the children of the Group. Instead, just replace the old Group with a new Group. If needed, you can prepare the new Group in a background thread.

   Doing it that way, it took 3.5 seconds on my computer to create another Group with 1,000,000 children and then replace the old Group with the new Group. However, there was still a bit of a lag spike due to all the new nodes that needed to be rendered at once.

   If you don't need to populate the new Group then you don't even need a thread. In that case, the swap took about 0.27 seconds on my computer.

As suggested here, the following will suffice:

With comment @derpirscher, I change my reader function with this code :

Try this please

It appears that you are using text fields so it hides data or sometimes it may overflow borders by black and yellow stripes

better to use SingleChildScrollView and for scrolling direction use scrollDirection with parameters Axis.vertical or Axis.horizontal

A deployment is a higher abstraction that manages one or more replicasets to provide controlled rollout of a new version.

As long as you don't have a rollout in progress a deployment will result in a single replicaset with the replication factor managed by the deployment.

Your setuptools version is likely to be yanked:

https://pypi.org/project/setuptools/60.3.0/

Not sure how to fix that without a working pip though.

Here is a possible solution.

To use a master password, you can use the loginUsingId function

Search the user by username, then check if the password matches the master password, and if so, log in with the user ID that it found

You have stumbled into a feature/bug in DispatchSemaphore. If you look at the stack trace and jump to the top of the stack, you'll see assembly with a message:

BUG IN CLIENT OF LIBDISPATCH: Semaphore object deallocated while in use

E.g.,

This is because DispatchSemaphore checks to see whether the semaphore’s associated value is less at deinit than at init, and if so, it fails. In short, if the value is less, libDispatch concludes that the semaphore is still being used.

This may appear to be overly conservative, as this generally happens if the client was sloppy, not because there is necessarily some serious problem. And it would be nice if it issued a meaningful exception message rather forcing us to dig through stack traces. But that is how libDispatch works, and we have to live with it.

All of that having been said, there are three possible solutions:

1. You obviously have a path of execution where you are waiting and not reaching the signal before the object is being deallocated. Change the code so that this cannot happen and your problem goes away.

2. While you should just make sure that wait and signal calls are balanced (fixing the source of the problem), you can use the approach in your question (to address the symptoms of the problem). But that deinit approach solves the problem through the use of non-local reasoning. If you change the initialization, so the value is, for example, five, you or some future programmer have to remember to also go to deinit and insert four more signal calls.

   The other approach is to instantiate the semaphore with a value of zero and then, during initialization, just signal enough times to get the value up to where you want it. Then you won’t have this problem. This keeps the resolution of the problem localized in initialization rather than trying to have to remember to adjust deinit every time you change the non-zero value during initialization.

   See https://lists.apple.com/archives/cocoa-dev/2014/Apr/msg00483.html.

3. Itai enumerated a number of reasons that one should not use semaphores at all. There are lots of other reasons, too:

   • Semaphores are incompatible with new Swift concurrency system (see Swift concurrency: Behind the scenes);
   • Semaphores can also easily introduce deadlocks if not precise in one’s code;
   • Semaphores are generally antithetical to cancellable asynchronous routines; etc.

   Nowadays, semaphores are almost always the wrong solution. If you tell us what problem you are trying to solve with the semaphore, we might be able to recommend other, better, solutions.

You said:

However, if the async function returns before deinit is called and the view controller is deinitialized, then signal() is called twice, which doesn't seem problematic. But is it safe and/or wise to do this?

Technically speaking, over-signaling does not introduce new problems, so you don't really have to worry about that. But this “just in case” over-signaling does have a hint of code smell about it. It tells you that you have cases where you are waiting but never reaching signaling, which suggests a logic error (see point 1 above).