[QGIS-Developer] Popup window within Processing crashes QGIS

[C Hamilton]

Nyall,

I have been working on an alternative KML/KMZ importing tool and a tool to
expand HTML tables within the description field containing tag/value
elements into fields in the table.  The reason for another importer is that
the GDAL implementation is in some sense too smart. The situation is that
if there are many folders in a KML, QGIS imports each as a layer and is
very slow at importing or crashes during the import if there happens to be
hundreds of layers. This also happens using ArcGIS. I am assuming that both
use GDAL and in some respects GDAL tries to do too much. Consequently, I
wrote this KML plugin to import KML/KMZ files in the way we wanted them.
The following is the capability prior to processing.

https://github.com/NationalSecurityAgency/qgis-kmltools-plugin

The biggest difference between the native import and this one is that
rather than create multiple layers for each folder of KMLs, I create one
point layer, one line layer and one polygon layer if required. I add an
additional field that contains the folder structure for each feature.This
makes the import very quick.

I have already converted this importer to processing. The second function
that expands HTML tables in the description field does a first pass to see
if there are any tables and makes note of the tags/fields to be created. It
then pops up a dialog box to allow the user to select what fields they want
expanded. They only way you could do this in processing, since I can't pop
up a selection box, is to expand all potential tags/fields, but the users
don't want to do this. They want to select which fields they want added and
they may not know which tags they want until they look at the list. This is
why I wont be able to do it in processing.

I have debated whether I should make this a separate plugin in or add the
functionality to Lat Lon Tools. I already have conversion routines such as
MGRS conversion and "Plus Codes" in Lat Lon Tools. What are your thoughts?
Should this be added to Lat Lon Tools or a separate plugin?

Calvin


On Fri, Aug 31, 2018 at 5:06 PM, Nyall Dawson <nyall.dawson at gmail.com>
wrote:

> On Fri, 31 Aug 2018 at 22:24, C Hamilton <adenaculture at gmail.com> wrote:
> >
> > Thanks Nyall!!! Unfortunately I was trying to make this a processing
> routine when I shouldn't have. It is good to know the boundaries. This
> function really requires user interactivity.
>
> Mind sharing the general function of the plugin? There may still be a
> way to make this work within Processing.
>
> Regards,
> Nyall
>
> >
> > Calvin
> >
> > On Thu, Aug 30, 2018 at 9:27 PM, Nyall Dawson <nyall.dawson at gmail.com>
> wrote:
> >>
> >> On Thu, 30 Aug 2018 at 23:38, C Hamilton <adenaculture at gmail.com>
> wrote:
> >> >
> >> > I have an algorithm that during execution gathers information from
> the data and then pops up a window for the user to select what the user
> would like to do.
> >> >
> >> > Is this possible in the Processing framework? I have tried doing this
> in processAlgorithm and it crashes QGIS. Here is how I call the popup
> window.
> >>
> >> No - this is not supported and goes against the very fundamental
> >> design of Processing. Argggh! ;)
> >>
> >> But seriously, Processing was designed with the intention that all
> >> user choices are made up-front. This allows algorithms to be nicely
> >> executed inside of models, without the model halting mid-way waiting
> >> for user input. It also allows algorithms, scripts, models, etc to be
> >> run from headless environments such as console scripts.
> >>
> >> In this case, you're getting a crash because you're trying to create
> >> GUI components from your algorithm which is being executed in a
> >> background thread. This is a big no-no in Qt land, and usually results
> >> in a crash.
> >>
> >> Nyall
> >>
> >>
> >> >         fieldsDialog = SelectionDialog(self.tableFeatures)
> >> >         fieldsDialog.exec_()
> >> >         items = fieldsDialog.selected
> >> >
> >> > Here is the beginning of the SelectionDialong class.
> >> >
> >> > class SelectionDialog(QDialog, FIELDS_CLASS):
> >> >     def __init__(self, feat, parent=None):
> >> >         super(SelectionDialog, self).__init__(parent)
> >> >         self.setupUi(self)
> >> >
> >> > Prior to Processing I passed in iface.mainWindow() as the parent. Is
> there a proper parent in Processing to pass? Perhaps this is the reason it
> is crashing.
> >> >
> >> > class SelectionDialog(QDialog, FIELDS_CLASS):
> >> >     def __init__(self, iface, feat):
> >> >         super(SelectionDialog, self).__init__(iface.mainWindow())
> >> >         self.setupUi(self)
> >> >
> >> > Thanks,
> >> >
> >> > Calvin
> >
> >
>
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