[Usability] Clickable area masks on icons with transparency?

[Steven Garrity <steven silverorange com>]

I’m certain this issue must have been discussed before, but I’ve been 
unable to find such a discussion. If this is the case, I apologize and 
would appreciate a pointer to any resources or archived discussion on 
the topic.

I’m a new linux user who has started with RedHat 9 coming from a 
primarily Windows (3.1 through XP) background. I also have some Mac 
(Classic and OS X) experience.

One of the first things I noticed about the GUI (after being pleasantly 
surprised by the overall refinement) was the clickable “holes” in icons.

It seems that the visual transparency of icons also serves as tactile 
transparency. You can only click on non-transparent portions of the 
icon. In theory, this sound ok. If you click on a folder, it is 
selected, but if you miss the edge of the folder, it is not selected. In 
practice, this turns out to be confusing and annoying.

Many icons had large transparent areas with complex shapes, often 
reaching right through or near the core of the opaque areas of the icon. 
See this diagram of the CD icon as an example: 
http://actsofvolition.com/images/gnome_icons.png

There are two separate, but related issues here. I brought this same 
issue up recently regarding Mac OS X. It was pointed out to me that it 
was the fault of the individual icon designer. As it turns out, the OS X 
icon format separates visual transparency from the clickable area – so 
an icon with lots of visual transparency can still employ the full 
square shape as clickable.

Mac OS X seems to have remedied this issue in the next update (10.3) of 
OS X. They now draw a selection box around the entire icon area, rather 
than just the icon itself. I assume this corresponds with a completely 
clickable icon are (http://macnet2.com/panther/pictures/choosingdoc.html).

So, there is the architecture of the icon format – is there separate 
functionality for clickable-transparency independent from visual 
transparency?

If so, I have two questions; Should this be the case? In what situation 
would you want clickable area to vary from visual transparency (I can 
think of some examples, but I’ll leave that aside for now). How should 
individual icon designers handle this power? Should they match clickable 
area to visual transparency, or should they maximize (use the full 
square area) the clickable area?

If this functionality does not exist, the question remains, should 
clickable area be maximized to the full area of the icon size (the full 
square), or should it match the shape of the icon object?

Any pointers to research, prior art, previous discussions, or rationale 
for the current implementation on this topic would be appreciated.

Thank you,
Steven Garrity
steven actsofvolition com