Forum: Ruby Canvas-like GUI in Rhodes?

I am a complete newbie to Ruby and Rhodes.  It seemed like Rhodes was
going to be a good tool for developing my application, but I am
concerned by the brevity of the list of widgets shown on the Rhodes
website, such as http://docs.rhomobile.com/rhoelements/addressbar .

They show 24 widgets, from AddressBar to WebView.  I don't see what I'm
seeking, which is the ability to draw a polygon that has a callback
associated with it.  I am more familiar with Perl programming, and a
good example of what I'm seeking is
http://search.cpan.org/~srezic/Tk-804.030/pod/Canvas.pod .

Are these widgets described on the Rhodes website all that's available?
Can gems such as Gosu and Rubygames be used with Rhodes?  I'm unsure
whether either of these has the Canvas-like functionality that I'm
seeking, but I'd first like to find out if they're even options on
Rhodes.

Thanks,
John