Hello guys and gals, I’ve just merged a new Window...

# compose-desktop

[Alexander Maryanovsky]

Hello guys and gals,
I’ve just merged a new Window/Dialog API with some improvements. It’s available in CMP 1.12.0-alpha01+dev4104
Here’s a short guide I wrote.
Feedback is welcome.

[Didier Villevalois]

Looked quickly at the API. Being able to auto-size a window is great! Thanks.

Do you think this will also fix https://youtrack.jetbrains.com/issue/CMP-8821 ?

[Alexander Maryanovsky]

Unfortunately no. I’d even say the new API makes this problem even harder to solve.
The problem there is that the first composition happens before the window has been given a size. In the new API you can size the window according to the content, so the content has to be composed, measured and laid out before the window can be given a size.

[Alexander Maryanovsky]

It’s just a problem that wasn’t considered when the LocalWindowInfo API was written, because it was written for Android, where the window size is typically fixed.

[Didier Villevalois]

It affects adaptive layouts, as currentAdaptiveWindowSizeClass() is based on LocalWindowInfo on desktop....

[Didier Villevalois]

What advice would you give me to workaround this? Currently my workaround if is not pretty...

[Alexander Maryanovsky]

I understand.
It’s fairly easy to check for zero size and handle this case differently, though.
There really is no way to know the size of the window when the first composition happens though, so it’s an actual case that needs to be handled, not a bug.

[Didier Villevalois]

So, the if I use to not do the first composition is the right way?

[Alexander Maryanovsky]

I don’t know what you do in that if.
What I think you should be doing is using a “default” or “preferred” window size in the first composition. This will allow sizing the window to the content.

[Alexander Maryanovsky]

To clarify, it’s a chicken and egg problem.
Adaptive layouts want the content to adapt to the size of the window.
The window, initially, wants to set its size to the preferred size of the content.

[Alexander Maryanovsky]

So someone has to be “first”

[Didier Villevalois]

In essence, I do if (LocalWindowSize != 0,0) { App() }

[Didier Villevalois]

Otherwise, there is an animation happening when the window appears.

[Alexander Maryanovsky]

In essence, I do if (LocalWindowSize != 0,0) { App() }

That will make it impossible to size the window to the preferred content size.

[Didier Villevalois]

Otherwise, there is an animation happening when the window appears. Because at first composition, we are COMPACT (because LocalWindowSize is 0,0) and at the second composition we are EXPANDED (for instance).

[Alexander Maryanovsky]

So don’t use COMPACT, use the window class you want to be at

[Alexander Maryanovsky]

and use the new Window sizing API to make that happen

[Didier Villevalois]

I don't know the window size class I need inside the composable tree. That's what currentAdaptiveWindowInfo is supposed to do. Are you saying I should completely bypass compose-adaptive on desktop?

[Alexander Maryanovsky]

I don’t know the window size class I need inside the composable tree.

Someone should specify that.

[Alexander Maryanovsky]

Again, it’s a chicken and egg problem.
Content: Hey, what’s the size class here?
Window: What size do you want to be? I’ll size myself to that.
Content: I don’t know yet, let me know the size class.
Window: I can’t let you know until you tell me your preferred size.
….

[Didier Villevalois]

I don't mind specifying a default size (say 800,600) and on later application start restore the last saved size. But then LocalWindowSize is always initialized to 0,0 at first composition anyway.