App resizing and external fullscreen

[klasma]

Up to iPadOS 15, apps had to explicitly support being fullscreen without black bars on an external display. The implication is that the OS couldn’t just change the aspect ratio of any arbitrary app without cooperation from the app. With Stage Manager, this somehow seems to have changed? How does this actually work, i.e. how does an app experience the resizing under Stage Manager, and why does such resizing work now while it previously didn’t?

What I’m interested in is to understand whether there are technical reasons iPadOS 16 on non-M1 iPads couldn’t use whatever logic it now uses for Stage Manager windows to change the aspect ratio of apps to the external display resolution (removing the black bars), outside of Stage Manager. That is, I can understand why the increased RAM and storage bandwidth of the M1 models may be necessary for multitasking under Stage Manager, but I don’t understand why resizing apps to external fullscreen (i.e. single-task) wouldn’t be possible on non-M1 if indeed such change of aspect ratio doesn’t require explicit app support anymore.

 

[symphony]

I think the feature for developers was called auto layout, which was introduced to iPad for a long time now. When they announced ARM for Mac at WWDC, they showed how the Documents 5 app allowed to freely change window size without developer doing the work on macOS. I think they said this was active preview with live adjustments, whereas iPad had a blur to hide the transition of changing window size.

Due to that, Apple was able to have resizing windows. Because essentially, all full screen apps is just one big window that fills the iPad display. iPad apps back then had to accommodate for different screen sizes and multitasking tiles.

They probably just want a consistent experience with Stage Manager.

 

[klasma]

I think the feature for developers was called auto layout

I’m aware of Auto Layout, but apps aren’t required to use it, and as you say it has already existed for a long time, so it doesn’t really clarify anything about what I’m asking. I’m also pretty sure that for an app to be displayed without black bars on an external monitor on iPadOS <= 15, just using Auto Layout is not sufficient (and maybe also not necessary).

 

[symphony]

I’m aware of Auto Layout, but apps aren’t required to use it, and as you say it has already existed for a long time, so it doesn’t really clarify anything about what I’m asking. I’m also pretty sure that for an app to be displayed without black bars on an external monitor on iPadOS <= 15, just using Auto Layout is not sufficient (and maybe also not necessary).

Not all apps have adjustable windows in iPadOS, just like macOS

 

[klasma]

Not all apps have adjustable windows in iPadOS, just like macOS

But I assume that more apps have resizable windows under Stage Manager than those apps that have no black bars on an external display under iPadOS 15 (because that’s only very few). For those resizable apps, it seems they could in principle be displayed without black bars on an external monitor, but aren’t (outside of Stage Manager). I’d like to understand whether that’s just an arbitrary limitation, or whether there is actually some good technical reason for that.

 

[symphony]

But I assume that more apps have resizable windows under Stage Manager than those apps that have no black bars on an external display under iPadOS 15 (because that’s only very few). For those resizable apps, it seems they could in principle be displayed without black bars on an external monitor, but aren’t (outside of Stage Manager). I’d like to understand whether that’s just an arbitrary limitation, or whether there is actually some good technical reason for that.

In my opinion, it is arbitrary. M1 iPads can switch to full screen mode for apps in Stage Manager with an external display. And the Mac mini with A12Z clearly has the capability to run multiple resizable windows and full screen windows. So older iPads should’ve been okay with what you suggested.

An M1 iPad is capable of running 8 apps simultaneously with an external display, but is limited to four with just iPad. We know an M1 can run more than those apps too. So I think it’s just Apple setting unfair limitations.