release 3.2: Qt6/QGIS 4 support and bug fixes

[fgianoli]

release 3.2: Qt6/QGIS 4 support, native setDataSource, SQL view & provider fixes

• Dual Qt5/Qt6 compatibility via qgis.PyQt + qualified enums (qgisMinimumVersion=3.20)
• Replace XML-based datasource patching with native QgsMapLayer.setDataSource():
  preserves auxiliary storage (manual label positions, data-defined overrides)
  and clears layer tree warning/memory indicators after reload
• Fix StopIteration on long PostGIS SQL views (WITH/window functions):
  memory layer fields now string(0) unlimited instead of string(250)
• Add missing providers: mssql, hana, db2, wfs, arcgisfeatureserver (vector);
  wcs, arcgismapserver, xyz (raster)
• Qt6 API fixes: fontMetrics().horizontalAdvance(), exec(), int coords in move()
• Replace deprecated QgsMessageBar.CRITICAL with Qgis.MessageLevel.Critical
• Use QgsWkbTypes.geometryDisplayString() for safer geometry type resolution
• Null/None guards on locale, mapLayer lookups, expression results
• Drop dead code (QgsMapLayerRegistry, qgisVersionOk), debug prints,
  Python 2 / PyQt4 shims, unused resources_rc import

[falkmielke]

The changeDataSource plugin is enormously useful for my work, and I much appreciate the update on this!

I could get the code of this PR to run on my machine; however, there was an issue with fontMetrics which I solved locally:

# (line 26)
from qgis.PyQt.QtGui import QIcon, QFontMetrics

# (line 309)
        idealWidth = QFontMetrics(QApplication.instance().font()).horizontalAdvance(txt) 

Here is the traceback:

AttributeError: 'QApplication' object has no attribute 'fontMetrics'
Traceback (most recent call last):
File "/QGIS/QGIS4/profiles/default/python/plugins/changeDataSource/changeDataSource.py", line 421, in run
self.populateLayerTable()
~~~~~~~~~~~~~~~~~~~~~~~^^
File "/QGIS/QGIS4/profiles/default/python/plugins/changeDataSource/changeDataSource.py", line 244, in populateLayerTable
self.dlg.layerTable.setCellWidget(lastRow, 0, self.getLabelWidget(layer.id(), 0, style=cellStyle))
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/QGIS/QGIS4/profiles/default/python/plugins/changeDataSource/changeDataSource.py", line 309, in getLabelWidget
idealWidth = QApplication.instance().fontMetrics().horizontalAdvance(txt)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'QApplication' object has no attribute 'fontMetrics'


Python version: 3.14.5 (main, May 10 2026, 18:26:20) [GCC 16.1.1 20260430]
QGIS version: 4.0.2-Norrköping Norrköping, exported

Apart from this small change, the PR worked with the versions indicated above. 🥳

[falkmielke]

(see comment on #25 ; these suggestions are the adjustments which worked for me to get the plugin running)

[falkmielke]

for fontMetrics to be used (below), I would suggest to add QFontMetrics:

from qgis.PyQt.QtGui import QIcon, QFontMetrics

[falkmielke]

This gives an error on the (almost) latest versions of QGIS and Python: fontMetrics have to be turned into an object QFontMetrics. The following worked for me:

        idealWidth = QFontMetrics(QApplication.instance().font()).horizontalAdvance(txt)

[falkmielke]

Suggested change

	idealWidth = QApplication.instance().fontMetrics().horizontalAdvance(txt)
	idealWidth = QFontMetrics(QApplication.instance().font()).horizontalAdvance(txt)

[falkmielke]

Suggested change

	from qgis.PyQt.QtGui import QIcon
	from qgis.PyQt.QtGui import QIcon, QFontMetrics

[fgianoli]

Thanks @falkmielke! Applied your QFontMetrics fix and bumped to 3.2.1 (commit a9dac49).