[Developers] plugins with no data produced

[Bert Bril]

Hi Fidel,

> I just have programmed a plugin with a fixed parameter and worked.
> But when in the plugin of user interface i add a list for choosing
> a value of that parameter, the plugin does not calculate anything and
> displays anything.

 From this description - being somewhat short - I understand that you 
tried to just add a UI class in the Init function of the plugin. That 
won't work.

The OpendTect user interface, like almost all modern user interfaces, is 
event driven. Roughly, this means that you describe:

1) What should be on the screen
2) What should happen on certain events

The program itself starts an endless loop, reacting on input from the user.

Probably one of the simplest examples of a UI in OpendTect is the 
uiHello plugin. More useful is the plugin you get when using:

% make PLAN_B=yes

So, if you look into plugins/uiHello/uihellopi.cc you will probably find 
the example you need to get started. Although it is possible to omit 
workign with the menu, sooner or later you'll want to add menu items, 
tool buttons, or tree items. I think the example also shows how easy it 
is to do that.


> What reasons could be if the message "no data produced" is displayed?
> The exact message is "no output data created"

Oh! Apparently, you are using the attribute engine because you're 
getting an error message that is produced by a part of the attribute 
engine (src/AttribEng/attribcubeexec.cc line 88). This message means 
that although the input parameters etc. for the AttribEngMan object were 
OK, when it actually executed there simply was no output. That can be 
due to lack of input data. I'd need to see more to say more. But my 
guess is, that if you get your user interface things right, like in the 
uiHello example, this will turn right too.


Bert