ThreadedProgressDialog

[fire]

Godot version:
master

Issue description:

Create a threaded progress dialog with 2 modes / 4 combinations.

1. Blocking or not blocking. Prevents the editor from being used but doesn't stop ui.
2. Background or foreground. Display in the middle of the screen or as a progress bar on the top right corner.

@neikeq Design review?

<neikeq> yes, i want it to block in this case

<neikeq> reduz: what's the use of BackgroundProgress if it does not block? how is it displayed in the UI?

<reduz> i think on the top right region a small progress is displayed

<reduz> its for background processes, Filesystem Scan uses it

<reduz> not very useful in general, though

<reduz> i guess what you want is a ProgressDialog that does not block and can be used from a thread

<reduz> maybe ThreadedProgressDialog

[neikeq]

2. Background or foreground. Display in the middle of the screen or as a progress bar on the top right corner.

We already have BackgroundProgress for a background progress dialog that doesn't block the main thread. What's the point of one that blocks the main thread?

[fire]

Example case: converting a scene to one mesh instance.

1. Not be able to modify the scene
2. Not block the main thread
3. Make it background so that the developer can see the editor 3d window but not actually edit
4. Make it background and allow the developer to edit the scene and when the system is done replace the scene. (I have an implementation of this), but it modifies a label to display progress rather than a dialog.

[fire]

I don't see a BackgroundProgress in the latest docs on https://godot.readthedocs.io/en/latest/index.html

[neikeq]

I'll use the term exclusive dialog to describe a dialog that captures all input, hence it "prevents the editor from being used".

What we have right now:

• ProgressDialog. The way it's designed is for tasks that block the main thread. It's an exclusive dialog. It will rely on a call to Main::iteration() when progressing for redrawing the ui. This is quite an ugly hack and it can cause serious trouble (like infinite recursion) when using MessageQueue/call_deferred. It also cannot be used from a function that would execute on every iteration (like _process and _fixed_process) unless you have some recursion guard (example).

• BackgroundProgress. It's being used by the FS scan thread. I don't know what it looks like. @reduz says it's a small progress dialog in a corner. It's not an exclusive dialog.

What we need: An equivalent of ProgressDialog that doesn't block the main thread but still acts like an exclusive dialog.

[fire]

Design 2

An exclusive dialog ("prevents the editor from being used"):

• do not block the main thread
• blocks user input
• Show ui in the middle of the screen.

A non-exclusive dialog ("does not prevent the editor from being used"):

• do not block the main thread
• does not block user input
• Show the same ui as BackgroundProgress as a small progress dialog in a corner

The desired implementation will take the non-exclusive dialog and make it exclusive.

[fire]

To allow threaded asset import, every instance of ProgressDialog should be replaced by the exclusive progress dialog that doesn't block the main thread.

Edit: Another part is to solve the dependencies of assets, but that's a different issue.

[Calinou]

What's the status on this now that #36640 was merged?

[fire]

I have not looked into this. Feel free to take this task.

[fire]

I have forgotten about issue. I think a new issue should be opening in the proposals for it.

[akien-mga]

I think this can be considered implemented by #36640.

[neikeq]

@akien-mga This is about the progress dialog, not resource loading. I don't see the relation between with that PR, unless I'm missing something.

[akien-mga]

Then this should be moved to a proposal on https://github.com/godotengine/godot-proposals, which can now use the threaded resource loader for a proposed implementation.