I've just come up against a "Setup Alert" while running setup-x86.exe
version 2.831. This dialog box seems to offer no way to go back and
address the cause of the alert; "OK" continues with the installation,
while "Cancel" ends the entire installation process immediately.

I think either the "Cancel" button should cancel the dialog and take
the user back to the previous screen (whence they can click "Cancel"
again if they wish to abort the entire installation), or there should
be an additional "Back" button that does so without breaking out of
the installation entirely.

More detail on what I did: I ran setup-x86.exe, and the "Resolving
Dependencies" step included installing libusb0 (apparently required by
libusb-win32, which I seem to already have installed). Clicking "Next"
on the Resolving Dependencies page produced the following alert box:

"In order to use libusb0, you must download and run the LibUSB-Win32
driver installer from:
https://sourceforge.net/projects/libusb-win32/files/libusb-win2-releases/1.2.6.0/libusb-win32-devel-filter-1.2.6.0.exe"

Not, as far as I know, needing any particular USB support in Cygwin, I
was planning on stepping back and removing the dependencies, so
clicked "Cancel". I expected this to dismiss the dialog box without
continuing the installation process.

I've attached a slightly redacted cygcheck.out; I don't think it's
relevant but I'm including it just in case.  This was produced after
letting the installation proceed, sadly. I've previously installed
some packages from Cygwin Ports, as well as faffing around by hand
with some other packages (git* and bash-completion), but I don't think
any of that should make a difference to setup-x86.exe's behaviour.

To be explicit, my issue is entirely with the dialog behaviour, not
with the the requirements of libusb0 and friends.

Adam