Dealing with async and things that should only run once

[RubberDuckShobe]

Hello, I am trying to make a simple updater for another app using egui with eframe, but I have absolutely no clue how to approach this.
It'll automatically do an update step-by-step (while showing the user what step it's at with a progress bar), so for example, it would do something like:

1. download the new version
2. extract the files
3. delete old files
4. copy new files

The thing I am confused about the most is how to deal with things that should only run once, like a function to download the latest version of the app I want to update. If I were to call that in the same place where the UI gets drawn, it would be called every single frame, which is definitely not good!
Another issue is that I'll also have to use async functions and I don't know how to make these work with the eframe/egui app, which doesn't use async.

How could I go about doing this?

[YgorSouza]

Usually you would model this like a state machine. You have to add fields to your app's struct that keep track of the current state, and then draw the UI accordingly. For example, this button from the demo app disables the UI for 2 seconds and then enables it again, by setting a field to the time at which the button was clicked, and then disabling the UI if it has been less than 2 seconds since that time.

egui/crates/egui_demo_lib/src/demo/window_options.rs

Lines 146 to 148 in 0bc59f5

	if ui.button("Disable for 2 seconds").clicked() {
	self.disabled_time = ui.input(|i| i.time);
	}

egui/crates/egui_demo_lib/src/demo/window_options.rs

Lines 58 to 61 in 0bc59f5

	let enabled = ctx.input(|i| i.time) - disabled_time > 2.0;
	if !enabled {
	ctx.request_repaint();
	}

In your case, you would either spawn a thread or something like a tokio task to do the operation in the background without blocking the UI, and give it some way to communicate progress information and results back to the main thread (like a mutex or an mpsc channel), then store the handle in a field of your struct so you know something is in progress while you're drawing the UI. I have this app that downloads images asynchronously, if you want to take a look: https://gitlab.com/ygor.souza/xkcd-viewer. The image part is a bit outdated since it targets an old version of egui, but the basic state management logic is mostly independent of egui. This is one way to do it, but there are others. You may also want to take a look at the http example from the demo app: https://www.egui.rs/#Http.

[RubberDuckShobe]

This is great, thank you!

…

On Sat, Apr 27, 2024, 22:13 YgorSouza ***@***.***> wrote: Usually you would model this like a state machine. You have to add fields to your app's struct that keep track of the current state, and then draw the UI accordingly. For example, this button from the demo app disables the UI for 2 seconds and then enables it again, by setting a field to the time at which the button was clicked, and then disabling the UI if it has been less than 2 seconds since that time. https://github.com/emilk/egui/blob/0bc59f578b907e357f118dba362d89d5e36f4c31/crates/egui_demo_lib/src/demo/window_options.rs#L146-L148 https://github.com/emilk/egui/blob/0bc59f578b907e357f118dba362d89d5e36f4c31/crates/egui_demo_lib/src/demo/window_options.rs#L58-L61 In your case, you would either spawn a thread or something like a tokio task to do the operation in the background without blocking the UI, and give it some way to communicate progress information and results back to the main thread (like a mutex or an mpsc channel), then store the handle in a field of your struct so you know something is in progress while you're drawing the UI. I have this app that downloads images asynchronously, if you want to take a look: https://gitlab.com/ygor.souza/xkcd-viewer. The image part is a bit outdated since it targets an old version of egui, but the basic state management logic is mostly independent of egui. This is one way to do it, but there are others. You may also want to take a look at the http example from the demo app: https://www.egui.rs/#Http. — Reply to this email directly, view it on GitHub <#4415 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKHUEXW64CKVZI66G3PRBVLY7QBIBAVCNFSM6AAAAABGZWNXNWVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TENBXG44TG> . You are receiving this because you authored the thread.Message ID: ***@***.***>