[R-gui] general design questions

[Antje]

Hi Michael,

thanks a lot for your answer.


> On Mon, Aug 18, 2008 at 6:56 AM, Antje <niederlein-rstat at yahoo.de 
> <mailto:niederlein-rstat at yahoo.de>> wrote:
> 
>     Hello,
> 
>     I try to develop a GUI with gWidgets (TclTk) but I guess my little
>     application already starts to be messy...
> 
>     First question: How shall I handle updates of widgets triggered by
>     event handling? So far, I simply took the widget-object I want to
>     update as a global variable but that's not a good style. Any
>     suggestions how to handle this?
> 
> 
> It's possible to specify a "user" object when registering the callbacks, 
> I think. The "user data" is then passed as the last parameter to the 
> handler. Another good way to control the scoping is nesting environments 
> (e.g. through closures). That is, your object does not need to be global 
> (in the workspace) but it can be in a parent environment. In fact, 
> global variables won't even work when you put your code into a 
> namespaced pacakge, because the namespace will be locked.
> 

Can you give me a simple example, please? I'm not sure if I understand 
correctly how this can work. (Or maybe there is already some kind of 
documentation I can check for these possibilities...)

> 
>     Second question: What are my possibilities to stay flexible? For
>     example: I though it makes sense to use a gpanedgroup for a
>     checkboxgroup with variable number of items (to make it scrollable
>     if it's getting too large). But this does not work like I thought
>     and the items simply disappear at the end of the panel.
> 
> 
> I don't think the paned group is what you want here. Split paned widgets 
> are to allow the user to control the allocation of space in a GUI, 
> usually in either the horizontal or vertical directions. If you're GUI 
> is growing too large, you'll need to make it so that only a portion of 
> the GUI is visible at once. One way to do that is with scrolled windows. 
> See the use.scrollwindow parameter for ggroup().

Oh, thanks a lot. I was not aware of the scrolling opportunity if the ggroup.

>  
> 
> 
>     Third question: How to structure the GUI? Builing, Sizing, Arraging,
>     filling with content (not every object has some initial content).
>     For example, I realized that I have to set the svalue for the
>     gpanedgroup after adding the objects.
> 
> 
> Well this is an art and depends on your GUI. Split panes are difficult 
> in that they require one to specify a numeric value for the split 
> position. This is a similar problem to specifying the initial size of a 
> window. 

Is there anything I can do beside, setting a fixed size with pixel values?
For example if I'd like to initially maximze the window... (I know that it's 
possible with TclTk).

> The simplest way is just to guess a good initial position. This 
> is usually not too bad. Adjusting the split automatically might not be a 
> good idea, since it should be under the control of the user.

Of course, I just set it initially.

Ciao,
Antje


>  
> 
> 
>     I don't know, but I have the impression to create my GUI quite
>     unstructured and I'm afraid to loose overview soon...
> 
>     The small examples for the usage of different components are very
>     useful but I'm looking for some hints on how to create a more
>     complex application (what to do when and how).
> 
>     Thanks a lot for every tip!
> 
>     Antje
> 
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