Re: [Plplot-devel] Qt5 support, strange driver output

[Alan W. I. <Ala...@gm...>]

On 2018-12-20 13:21-0800 Alan W. Irwin wrote:

> On 2018-12-20 18:56-0000 António Rodrigues Tomé wrote:
>
>> Hi Alan
>> I do not completely understand the need of using a mutex in the qt driver
>> however
>> without any change in the actual driver approach it is easy to allow the
>> driver to work well within a qt app and also in any other c or c++ program
>> if in the file qt.cpp function  bool initQtApp( bool isGUI )
>> we add after the ++appCounter; line (line 90)
>> the instruction
>>    if(appCounter == 1 && qApp != NULL) ++appCounter;
>> this will prevent the call
>> delete qApp;
>> when one closes the driver within a qt application, that would crash teh
>> application,  and it does  not conflict with the actual behavior of the qt
>> driver it onnly takes account for the fact that there is a qApp that was
>> not started by the driver.
>
> Hi António:
[...]
> So from the point of view of a non-expert for this code, I would
> suggest if you think the mutex is no longer needed because of your
> change, then go ahead an remove it to see whether that combined change
> passes all tests you care to make including ideally running the
> comprehensive test script as documented in
> doc/wiki_source/Testing_PLplot.

With regard to the mutex, I have included what Alban initially said about
it way back when.

>From his comment my guess is the mutex is a necessity to keep the Qt
components of PLplot thread-safe because the PLplot core is not thread
safe (although fixing that bad state of affairs is on our long-term agenda).
And subsequently there was a whole lot of plplot-devel traffic about
properly setting up that mutex with no question from anyone about its
necessity.

Anyhow, forget my naive idea above that you might want to drop the mutex.

Alan

---------- Forwarded message ----------
Date: Fri, 20 Mar 2009 17:00:49 +0000
From: Alban Rochel <a.r...@im...>
To: Alan W. Irwin <ir...@be...>
Subject: Qt driver update

Alan,

I've made a break from QSAS for an hour and I've made a couple of improvements 
to the Qt driver.

- I've introduced a mutex to make some parts thread-safe (I haven't checked if 
all the driver was).
- Someone noticed that when 2 qtwidgets were running on 2 streams, closing them 
didn't close the driver properly. This should be fixed by now. When qApp is 
run, all the qtwidgets created before are tagged as being run, and so the 
driver shouldn't try to run one qApp per widget.

Cheers,

Alban

__________________________
Alan W. Irwin

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
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