[plt-scheme] extending gui.ss

The gui.ss teachpack is by far the worst software I ever designed and 
released. Mea culpa. It'll go away. -- Matthias


On Dec 30, 2005, at 7:48 PM, Prabhakar Ragde wrote:

> I recently had a question from a teacher in Germany about my 
> extensions to the gui.ss teachpack, which made me realize that I don't 
> understand gui.ss as well as I should.
>
> Callbacks associated with MrEd objects are provided with the object 
> and the event which triggered the callback; gui.ss provides just the 
> event to the user-supplied callback function. HtDP readers don't know 
> what to do with this and have to ignore it. I thought it might make 
> sense, for a button, to provide the button to the user-supplied 
> callback function. Then one function could handle multiple buttons.
>
> But a user-defined button, as far as users of gui.ss are concerned, is 
> not a button% object, but a gui-item structure. So I need some way, in 
> the rewritten version of gui.ss, to take a button% (provided by MrEd 
> when the button is clicked) and find the corresponding gui-item so 
> that I can provide it to the user-supplied callback function. I don't 
> quite see how to do this. Can someone help? Many thanks. --PR
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