Re: multithreading with gtkada

[evangeli <evangeli@cnam.fr>]

thanks for your response
i used protected type to prevent two tasks from making gtk calls at the 
same time but that doesn't seem to work

any idea?


Warren W. Gay VE3WWG wrote:

> evangeli wrote:
> 
>> hi all
>>
>> it seems that gtk doesnt support multi-threading (see 
>> http://www.faqs.org/faqs/x-faq/part7/section-15.html).
> 
> 
> I believe that Gtk does support tasks, but on UNIX platforms,
> Gtk will make use of the Xlib (as the ref above shows). This
> library I believe is now thread safe on _some_ platforms,
> but most certainly NOT on all of them.  I would certainly
> not depend upon it for portable code.
> 
>> My problem is the following :
>> my app opens a windows, which on the show event launch a task wich 
>> makes a long computation. The window also contains a cancel button 
>> which can be pressed to abort this task.The problem is that i would 
>> like this task to make X-Call, and that is apparently not possible and 
>> give me unavoidably the following error message:
>> ----------------------------------------------
>> Xlib: unexpected async reply (sequence 0x9fe)!
>> ----------------------------------------------
>> i havent found any solution which doesn't use several tasks.
>>
>> 1) Am i clear?
>> 2) Do u have any idea of a different way to do that?
>> 3) why this cruel destiny?
>>
>> thanks for any response
> 
> 
> Your problem requires some careful Ada programming. You will need
> to segment your application so that one or the following
> approaches are used:
> 
>  - Only one task does Gtk (GUI) operations
> 
> or
> 
>  - You use an Ada technique to make certain that only one Ada task
>    is doing a Gtk operation at any given instance (protected objects
>    perhaps).
> 
> Sounds like you need the second approach. You can run into the same
> situations when trying to use curses (text mode screens).
>