Hi Lars -
I hazard a guess, that you want to execute some action after a /project/
has finished loading.
You might have a look on how to execute macro's after open, save or
close events for the project:
In the project properties, you can enable macro's and write some python
code that will be stored in the project:
Example: (Open an attribute window with data from layer 'kommune" after
the project has finished loading)
|#--- macro start --- from qgis.core import QgsProject from qgis.utils
import iface def openProject(): layers =
QgsProject.instance().mapLayersByName('kommune') layer = layers[0]
iface.showAttributeTable(layer) def saveProject(): pass def
closeProject(): pass||#--- macro end ---|
Den 21-08-2019 kl. 14:15 skrev Lars I. Nielsen, LIFA A/S:
Hi bold developers of QGIS.
I’ve recently begun digging into utilizing the event (signal) model of
QGIS (3.4).
And I’ve encountered a number of frustrations, as the events don’t
work the way they’re supposed to, at least according to the available
documentation (https://qgis.org/pyqgis/master/core/index.html).
E.g., the event “layerLoaded” on the project instance with the
description “/Emitted when a layer from a projects (sic) was read/”,
which to me indicates, that the loading is done (due to the use of
“loaded” and “was”).
But the event is emitted before the loading of the layer is done, and
you are therefore unable to find the layer it concerns.
Another example is the event “metadataChanged” on a loaded layer,
which again to me indicates a past/done action (due to the use of
“changed”). But again, it’s emitted before the change actually takes
place, and the changed metadata isn’t available.
If the two events are indeed preload events, their names should
instead be something like “layerLoading” and “metadataChanging”, or
even “layerPreLoad” and “metadataPreChange”.
Is there a guide somewhere to tell how the event system is envisioned,
and which events are emitted pre-action and which are emitted
post-action ?
Or must I (hopefully not) take a deep look into the QGIS source code
itself for this kind of information ?
In general, pre-action events are of limited use, except when it comes
to deletions and destructions. For loading and changing stuff,
post-action events are almost always what you need.
Med venlig hilsen
Lars I. Nielsen, LIFA A/S
GIS-konsulent, FME Certified Professional
Geoinformatik
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