Re: Need info about Ada tasks

[Fionn Mac Cumhaill <invisible@hiding.from.spam>]

On Fri, 26 Sep 2008 06:21:54 -0400, Stephen Leake
<stephen_leake@stephe-leake.org> wrote:

>Fionn Mac Cumhaill <invisible@hiding.from.spam> writes:
>
>> I am using the MingW Ada compiler and the GWindows packages on Windows
>> XP.
>>
>> I am writing a simple program which observes a table in SQL Server
>> 2000 and lists its rows to a visible screen display. I need a simple
>> task structure that can update the display periodically, with a
>> specified wait time between updates. I need to be able to abort the
>> display task at any time when the display is not being updated.
>
>Mixing tasking and GUI events can be problematic; only one thread
>can call GUI functions.
>
>The canonical solution to your problem is to use a Win32 timer, and
>update the display in the timer event handler function. 
>
>Then "abort the display task" becomes "disable the timer".
>
>Although Dmitry solved your immediate problem, it might be better to
>use a different example problem to study tasking.

Mixing tasking and GUI events does indeed cause problems. The very
first subroutine call in the task object which can cause a Gui event
does not return when called.