wxGUI/lmgr: fix saving web service layer as raster map

[tmszi]

Describe the bug
Saving web service layer as raster map fail.

To Reproduce
Steps to reproduce the behavior:

1. From the GUI Layers pane toolbar launch Add web service map dialog
2. Hit Add default button
3. Choose OSM-WMS item from the load profiles ComboBox widget
4. Hit Connect button
5. From the tree list of layers choose some layer e.g. OpenStreetMap WMS - by terrestris
6. Hit Add layer button
7. From the Layers pane choose added web service layer OpenStreetMap WMS - by terrestris and by right mouse click invoke layer menu and choose Save web service layer menu item
8. See error

Traceback (most recent call last):
  File "/usr/lib64/grass84/gui/wxpython/lmgr/layertree.py",
line 862, in OnSaveWs

parent=self, layer=mapLayer, giface=self._gifaceForDisplay
AttributeError
:
'LayerTree' object has no attribute '_gifaceForDisplay'

Expected behavior
Saving web service layer as raster map should work.

System description (please complete the following information):

• Operating System: all
• GRASS GIS version: 8.4.0dev, 8.3, 8.2

[wenzeslaus]

This looks wrong. It is accessing a private attribute of self.mapdisplay. The "GRASS interface" references are meant to be shared to objects you create when appropriate, but not the other way around. self._giface like on line 871 would be how the code usually looks like.

[tmszi]

This looks wrong. It is accessing a private attribute of self.mapdisplay. The "GRASS interface" references are meant to be shared to objects you create when appropriate, but not the other way around. self._giface like on line 871 would be how the code usually looks like.

Yes I know about it. Original arg self._gifaceForDisplay point to LayerManagerGrassInterfaceForMapDisplay class instance which is not avilable as private atribute for LayerTree class instance. self._giface atribute point to LayerManagerGrassInterface class instance.

Should I initialize a new LayerManagerGrassInterfaceForMapDisplay class instance or use existed self._giface atrib as save web service layer class giface param arg?

[petrasovaa]

This is probably a more correct solution, but I did just brief testing.

[wenzeslaus]

The callback is actually a factory method so in a sense it is similar to constructor. In the context of giface concept, constructors should generally get the right giface rather than try to create it themselves. This moves creation of giface out of the callback and adds giface as its parameter, so it looks like the right solution. It also removes the duplicate code between the two callbacks which is nice and usually a good sign.