[Python] Labelling for linestring are rendered after

[lbartoletti]

Describe the bug

We use a python script to add labels and it works for all geometries except linestring where labels are not displayed until we modify the labeling properties.

How to Reproduce

1. Add a line
2. Execute this python script:

pal_layer = QgsPalLayerSettings()
pal_layer.fieldName = iface.activeLayer().fields()[0].name()
pal_layer.enabled = True

labeler = QgsVectorLayerSimpleLabeling(pal_layer)

iface.activeLayer().setLabeling(labeler)
iface.activeLayer().setLabelsEnabled(True)
print(iface.activeLayer().labelsEnabled())
# not necessary
iface.activeLayer().triggerRepaint()

QGIS and OS versions

All 3.X versions and OS

Additional context

Initial problem reported from Oslandia/labelconnector#13

[nyalldawson]

Check the label placement option -- the default is not applicable/usable for line layers.

e.g.

pal_layer.placement = QgsPalLayerSettings.Curved

[lbartoletti]

@nyalldawson Thank you. You're right, the default is not applicable for line layers. Shouldn't we propose a(n alternate) default for linestring too?

[nyalldawson]

@lbartoletti can you elaborate?

[lbartoletti]

@nyalldawson
You said the default is not applicable/usable for line layers (is the default is QgsPalLayerSettings::AroundPoint?)

So, if it's possible - I don't know this part of QGIS code - add a conditional default something like :
mDefaultPlacementMember ( layer->.geometryType() == QgsWkbTypes::LineGeometry ? QgsPalLayerSettings.Curved : QgsPalLayerSettings::AroundPoint )

But really don't know if this will change something for the python api.

Well, for my part, I consider that the problem is solved because it is a problem of using the python api.