27.1 "GUI" library

[njr0]

It took me a little while to understand what we were supposed to do in this exercise. I think a couple of things confused me:

1. The button had a callback, which made me think we were actually going to implement something you could click and which would use the closure to print "You clicked the button!" But (unless I still haven't understood), there's none of that: it presumably just takes a callback because a real GUI would. But it threw me off.

2. It wasn't really clear to me at first what I could do with buffer because it wasn't quite similar enough to your example. In the end, I tried write_all on it which didn't work, and the compiler suggested write_fmt, from std::format, so I looked up the documentation for that and figured out that I could use write! (which I actually did) or writeln!, which seem to be what you want.

Maybe this is all good because not understanding and looking things up is all part of development anyway. And I did get there. But I feel like I got quite lucky by trying write_all (and write, in fact), and if I hadn't done that, I don't think I'd have known what to do.

[djmitche]

I agree regarding the callback. It'd be great to find a way to use Box<dyn FnMut()> in the example, but this isn't it. Making the example more complex to allow clicking on the button would add a lot of complexity and not work in the playground. So, we should probably remove that.

Perhaps the second point could be solved with a hint in a comment?

// HINT: use `write!(buffer, "a fmt string")` to write into a buffer.

[njr0]

Yes, I either remove the callback or put a comment right by it (probably in both places) pointing out that it's unused in this code.

Unless figuring out how to use buffer is a key part of the exercise (which it seems to me, it probably isn't) I think a hint like that would be helpful, yes.

[mgeisler]

Hey Nick! Yeah, I wish I had found a nice way to integrate a click on the button... but doesn't seem feasible so I agree we should remove it. Could you send a PR to clean it up?

[njr0]

Happy to take a crack at it, yes, but probably not today.

[mgeisler]

No rush! 🙂 Thanks for all the feedback! It is super valuable because you see the material through fresh eyes and you can thus point out many things I have not seen.

[njr0]

Likewise, thanks for the course. It's excellent (and I hope you realise the feedback is because I like it and want to improve it).

[mgeisler]

I'm very grateful for the feedback! Writing up detailed feedback takes more time than people think, so thank you for this!

The Rust community has been amazing in helping us improve the course! This is one of the things I tried to highlight in the recent blog post about the course.

[njr0]

So I was just looking at this and wondering what the best way to fix it is.

Presumably the callback isn't really right anyway: it's just using println!, but I'm guessing you'd really want to write that into the GUI/TUIsomewhere rather than printing it to the terminal or wherever.

So I think I'd be tempted to remove the callback completely and just add a note in the text that here we're only "drawing" a (textual) GUI and that in reality you'd pass a callback to the button. And I'm guessing that callback would actually need to be called with some kind of reference to the window or a widget it was going to write into and cause a refresh?

I'll do something brutal and you can see what you think.

[mgeisler]

Thanks for #1293, it looks good!

[njr0]

Done. See what you think.