From: Ryan Leavengood <leavengood@...>
Date: 2006-05-18T01:29:06+09:00
Subject: Re: Need help designing UI

Over the years I'm sure there has been invented countless ways of
doing what you are asking, but I am personally most experienced with
the GUI system on BeOS, which I think is a very nice design.

Essentially all communication between various parts of the system
(from the OS to applications and back, from applications to their
windows and back, from windows to the GUI components and back) is done
via messages. A looper class is used to loop over messages coming in
and then the handling of these messages are delegated to a handler
class. On BeOS frequently the looper and handler are the same class.

Messages are handled first by their direct recipient (for example a
mouse down would be handled first by the component being clicked on.)
If the message cannot be handled by that recipient, it is passed up
the inheritance hierarchy until it is handled. Usually messages that
are used within an application itself are targeted directly to the
window, and then the window can delegate to the appropriate component.

So for you example, the "Close Window" toolbar button would have a
message with an associated CLOSE command constant, with the target of
the message being the window. When the button is clicked, the CLOSE
message will be sent to the window and the handling of that message
will close the window (of course.) The nice thing about this is that
the CLOSE message could be used from other places without having to
change how it is handled within the window.

Ryan

On 5/17/06, Scott L Holmes <scottlholmes@gmail.com> wrote:
> Hi,
>
> I'm working on a user interface and I'm hoping I can get some
> feedback/advice. I have 3 main classes: Viewer, Toolbar and
> ToolbarButton. Given that an instance of Viewer has an instance of
> Toolbar and that Toolbar has a collection of ToolbarButtons, I'm trying
> to decide how I want to implement the workflow for the "Close" process.
> The creation of all these instances is all rather "pretty" at the moment
> but no instances really "knows" or cares about the other. (parts is
> parts!)
>
> So, consider when the user clicks a "close window" ToolbarButton.
> Somehow the Viewer must be informed that its time to close the window.
>
> For some reason, I'm trying to avoid keeping a reference to the Viewer
> in the button (like with a call back). I'm hoping for a somewhat more
> interesting design. I've tried a variety of things over the years but
> I'm curious what others have tried, got working and generally like.
>
> Any comments would be greatly appreciated.
>
> Scott