unjokingly I think the fact that we removed grayed out buttons for "the button just doesn't appear" is one of the more confusing UI trends of our day and the sight of a grayed out button warms my heart
> Reconsider disabled controls. Disabled controls can be hard to use because users literally have to deduce why they are disabled. Disable a control when users expect it to apply and they can easily deduce why the control is disabled. Remove the control when there is no way for users to enable it or they don't expect it to apply, or leave it enabled, but provide an error message when it is used incorrectly.
> Tip: If you aren't sure whether you should disable a control or provide an error message, start by composing the error message that you might provide. If the error message contains helpful information that target users aren't likely to quickly deduce, leave the control enabled and provide the error. Otherwise, disable the control.
Unfortunately, that nuance has been lost in the modern version of the guidelines with no mention of disabled buttons at all [2]
Microsoft had some excellent guidance[1] on this:
> Reconsider disabled controls. Disabled controls can be hard to use because users literally have to deduce why they are disabled. Disable a control when users expect it to apply and they can easily deduce why the control is disabled. Remove the control when there is no way for users to enable it or they don't expect it to apply, or leave it enabled, but provide an error message when it is used incorrectly.
> Tip: If you aren't sure whether you should disable a control or provide an error message, start by composing the error message that you might provide. If the error message contains helpful information that target users aren't likely to quickly deduce, leave the control enabled and provide the error. Otherwise, disable the control.
Unfortunately, that nuance has been lost in the modern version of the guidelines with no mention of disabled buttons at all [2]
[1]: https://learn.microsoft.com/en-us/windows/win32/uxguide/top-...
[2]: https://learn.microsoft.com/en-us/windows/apps/develop/ui/co...