[Jprogramming] gl paint handler and errors

[Henry Rich]

For isidraw controls, events continue during suspension.  I don't 
remember about isigraph for sure.  My recollection is that events 
continue for isigraph too, and that what is special about isigraph paint 
controls is that they are given priority, going ahead of any other 
pending events, so that the graphics can be drawn while the jqt is still 
in its analog of the paint-handler.

Henry Rich

On 5/19/2016 7:27 AM, bill lam wrote:
> c++ jqt side did not know what had happened on the j engine so it will keep
> on calling J on paint.  You need to make j paint verb a no-op after the
> first popup.
>
> For debug suspension, you may want try catchd instead of catch. suspension
> in the presence of events is rather troublesome. IIRC all events except
> paint are discarded during suspension, so that you may still get infinite
> in suspension.
>
> what I used to do is set
> wdinfo_z_=: smoutput_z_
> in order to debug gl paint error.
> On May 19, 2016 5:28 PM, "Raul Miller" <rauldmiller at gmail.com> wrote:
>
>> So... maybe it would make sense to replace
>>
>>        wdinfo 'wdhandler';'error in: ',wd_fn,wd_err
>>
>> in wdhandler with something like
>>
>>        if. -.wdquery 'wdhandler';'error in:
>> ',wd_fn,wd_err,LF,'continue?' do.throw.end.
>>
>> ?
>>
>> Except... I tried that, and throw. was not sufficient to stop the
>> infinite condition with debugging disabled, and that line of code
>> never runs with debugging enabled. So there is something else going
>> on, also...
>>
>> Perhaps the best compromise for development purposes would be to
>> disable the offending handler (erase the name) if the user elects
>> cancelling out of it?
>>
>> Thanks,
>>
>> --
>> Raul
>>
>>
>> On Wed, May 18, 2016 at 6:36 PM, bill lam <bbill.lam at gmail.com> wrote:
>>> the popup dialog box is raised by a try catch block in the verb
>> wdhandler,
>>> since it does not throw an error after the popup, there is no suspension.
>>> the gl area partially hidden by the popup box is repainted and since the
>> gl
>>> paint or any other jqt events has no knowledge that there has been an
>> error
>>> in j wdhander being caught so there is an infinite loop.  You may add
>> some
>>> codes in the j paint verb to detect that error condition.
>>>
>>> this had been reported but fixing it is a low priority.
>>> On May 19, 2016 5:09 AM, "Raul Miller" <rauldmiller at gmail.com> wrote:
>>>
>>>> Currently, if I am using the gl commands for an isigraph control, and
>>>> there's an error, I get behavior which I do not understand.
>>>>
>>>> (1) I get a popup telling me that there was an error (and giving me
>>>> the details of the error.
>>>>
>>>> (2) I only have an "OK" option on that popup.
>>>>
>>>> (3) When I click "OK", execution resumes as if there were no error
>>>> (presumably on the line following the line with the error.
>>>>
>>>> This quickly leads to an infinite loop condition where my only option
>>>> is to shut down J.
>>>>
>>>> At the very least, I think I should get an option to have the error
>>>> stop execution somehow.
>>>>
>>>> (13!:0]1 avoids this problem, but why was it a good idea to make me
>>>> lose control of the J session in the first place?)
>>>>
>>>> (I'm not sure if this goes in jsource, since I think this is a jqt
>>>> issue, not a j engine issue. Please let me know, though, if there's a
>>>> better forum for this topic.)
>>>>
>>>> Thanks,
>>>>
>>>> --
>>>> Raul
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