yeah, I’ve had this, an it’s in part because of the windows system in mac os.
when you alt tab, you move between the “main” windows of opened apps, and if you have apps with several windows, it’ll open the top one, top one being most of the time the last focused or last opened.
so say, you have 2 safari windows opened, you alt tab to safari, you’ll get the top one / last used in focus.
in SU on mac, most toolbars and side panels are technically independant windows too. close the drawing space, they’ll stay.
in the PC interface, toolbars and panels are sub-windows. they aren’t independent, you can’t close the drawing space and keep the toolbars, it’s all or nothing
what seems to happen is that at times, when coming back to SU, the window that get focused is not the main drawing one. While SOME toolbars and panels dont allow you to ficus them (click on any side panel and it’ll focus the drawing space), SOME like th extended toolbar can be focused.
why the bug then ?
shortcuts only work if the main drawing window is selected. select another one, like the extended toolbar, and you’ll see, no shortcuts.
shortcuts (I press space or C and get a tool)
no shortcuts. I get the error sound.
I get this situation sometime at start too. if I launch SU and while it’s launching, I check something else, when I go back to SU by clicking the dock icon, the drawing window is not focused. My guess is, it’s the first one to open, and mac os will give me focus on the most recent one, often the extended toolbar.
I usually click at random in the drawing space then, it’s a reflex at this point. Again, it doesn’t happen all the time, I’ve noticed it’s more often if I’m on both screens, but not consistently. I guess some windows have this “focus stealing” behaviour, not all.
I wonder if there is a way to force the drawing window to always be focused (to be considered as “main” one) instead of the top / most recent / last focused one. I’d say probably, since the side panels already work that way, any idea @colin ? (some summer homework for the devs 
)