When you have an iPad sitting next to a Mac, if you push your cursor with the trackpad on the edge, it can move to the iPad.

The question is: what sorcery is MacOS using to figure out in which side the iPad is sitting? I did not tell MacOS this at all, and it just figured it out.

@Migueldeicaza I believe it’s using the UWB (U1) locator to determine approximately which edges they have in common.

@Migueldeicaza They silently rolled out Ultra Wide Band Location Services in Macs and other devices for a while now. See https://9to5mac.com/2022/01/28/macos-12-3-hints-at-ultra-wideband-technology-coming-to-macs/

@Migueldeicaza It’s not. Try to push it to the opposite side instead (you may have to sleep are re-wake the iPad to reset the service). 😁 Smart and sneaky!

@Migueldeicaza I read somewhere that it’s just guessing. If it is not connected, if you push the left edge, it assumes the iPad is on the left.

@Migueldeicaza i think it’s bluetooth rss.

@arroz @Migueldeicaza Just tested this and I can indeed push through the left AND the right edge of my Mac screen.

@xot @arroz @Migueldeicaza … I did not think that this worked because the iPad is usually *below* my main screen. Diabolical.

@Migueldeicaza
It probably checks your mouse movements. If you react to the border or keep going. It can learn a lot in the few milliseconds before your brain adjusts your movements. Slick though if it's doing it without you noticing. If our brain implies it's hardware and it isn't, that's really nifty.
Don't have a mac or ipad, but it made me think about the problem.

@glyph @xot @arroz @Migueldeicaza this is a beautiful example of Apple getting the intersection right.

We assume it’s magic. But it’s not. It’s accounting for our little money brain being easily tricked.

@Migueldeicaza @Sempf It doesn’t figure it out. It literally guesses that’s the direction because it’s the direction you’re “pushing” the mouse onto the iPad. You could theoretically “push” to the left (iPad on the right) and it’ll work. But our instinct to move the mouse the correct direction lets macOS infer where the iPad is. IMO it’s a pretty clever trick requiring zero logic to be added to the feature.

@Migueldeicaza Reset everything and then try pushing against the other edge instead.

@grork @glyph @xot @Migueldeicaza Yep. It’s fascinating how the force required to break though the barrier between devices is high enough to make you not go over the wrong side unless explicitly testing if it works (that’s how I found out about it), but low enough to seem natural if you’re pushing it through the correct side.

@siracusa @Migueldeicaza It’s so obvious but so clever. Classic Mac ingenuity.

@Migueldeicaza I've actually lost my cursor when it did this without me wanting it to. Then I've remembered to look at my iPad

@Migueldeicaza it works if you push your cursor through the other edge as well. It’s depending on you to pick the proper edge and going from there. 🙃

@Migueldeicaza You could check your display configuration to see if it was coincidental: https://cdsassets.apple.com/live/7WUAS350/images/macos/ventura/macos-ventura-system-settings-displays-arrange-displays.png

Image source: https://support.apple.com/en-us/102459

Maybe experiment with physically placing the iPad behind / in front of / left of / right of the Mac. If it magically adapts, well: since the hardware support goes all the way back to Intel 2016 Macbooks, it’s probably some older kind of Bluetooth communication and sensor readings going on.

@danielpunkass @siracusa @Migueldeicaza I love that tech people (including myself) immediately assume that it’s doing some advanced complicated smart thing, when it’s really just using really good heuristics and UX.

We could all learn a lot from this one feature.

@Aaron @Migueldeicaza @Sempf This is what actual design is.

@Migueldeicaza it gets even wilder with multiple iPads and it figuring that out too!

@Migueldeicaza –

(Or did you?) 👀

@Migueldeicaza it just assumes you’re pushing to the right edge.

@Migueldeicaza it goes by the folkiest time you push off the edge of the screen. Is a psych trick as most people move towards the iPad. You can make it work in reverse if you try.

@Migueldeicaza (right as in “proper" not opposite of left)

@Migueldeicaza It's actually... guessing - OS assumes that if you stubbornly push cursor to some specific side of the screen AND you have iPad awake somewhere in your network - then it's 95% chance you want to move the cursor 🤓

Sometimes the simplest solution just works 🤷‍♂️

(I think that how it worked initially, maybe indeed they're also added UWP into the equation)