Re: Properties

[Maciej Sobczak <see.my.homepage@gmail.com>]

On Dec 2, 11:26 am, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:

> > Why do you expect to get better guarantees from GUI than from stdout?
>
> Because in all Ada compilers I used so far this was safe.

Safe? What is the benefit of safe if at the same time it's pointless?

Put ("My ");
Put ("name ");
Put ("is ");
Put_Line ("Maciej");

I have multiple tasks doing it. What is safe for you? For me "safe"
means "not corrupting the information" and the above sequence produces
a single piece of information.

There is no point in Text_IO to be internally synchronized, because
the granularity of synchronization can be defined only at the
application level. And once this is done, it is also sufficient and
then any internal synchronization is a waste.

Similar reasoning applies to GUIs. Imagine a graphical display of
multi-line log messages. There is no point for such GUI to be task
safe, because GUI has no understanding of the logical granularity of
what is being displayed.

> A "reasonable" implementation of Text_IO queues I/O requests to some
> internal or external task/driver. I want same sort of design for graphical
> requests.

Not necessarily. And there are lots of data structures that have to be
acted upon until you come close to the driver. These data structures
are vulnerable to corruption.

> GUI is natively multitasking:
>
> 1. actions invoked by its controls are not instant: progress bar
> 2. some controls are active objects: animation widgets, visual effects,
> tooltips, hovering etc
> 3. indication of asynchronous events and data: oscilloscope

How is that any different from standard output?
How is your oscilloscope any different from the "top" utility that
displays the state of many processes on the text terminal? It is not
different and therefore does not need any additional guarantees.

--
Maciej Sobczak * http://www.inspirel.com