Hi all,
My name is Yoshimi, a company employee based in Nagoya, Japan. I'm not a core
GIS developer, but I've run into an issue during a project and would appreciate
any pointers from this community.
I'm running into an issue where simple callout labels on LineString features
fail to render at all when generated via a headless QGIS batch process (PyQGIS,
Linux container), while the exact same .qml style and the exact same data
render the callouts correctly when loaded manually in QGIS Desktop.
Environment:
* QGIS Desktop version (works correctly): 3.28.0, Windows
* QGIS server/headless version (fails): 3.22 (Ubuntu 22.04 apt package,
qgis + python3-qgis), running in a Docker container, driven via PyQGIS
(QgsApplication headless, no GUI event loop)
* Data source: PostGIS, LineString geometry, EPSG:6677
* Output: PDF via QgsLayoutExporter (print layout export)
Label/callout configuration (rule-based labeling):
<placement priority="5" placementFlags="10" placement="6" dist="30"
overlapHandling="AllowOverlapIfRequired" .../>
<rendering unplacedVisibility="1" obstacle="0" .../>
<callout type="simple">
... anchorPoint="point_on_exterior" labelAnchorPoint="point_on_exterior"
minLength="0" offsetFromAnchor="0" offsetFromLabel="0" ...
</callout>
Symptom:
* The line geometry itself renders correctly in the output PDF.
* The callout (leader line + label box) is completely absent in the
batch/server output — not partially clipped, not overlapping with anything,
just not drawn at all.
* No errors or warnings appear in the QGIS process log during style loading
(layer.loadNamedStyle() returns success) or during layout export.
* Forcing unplacedVisibility="1" (always show, even if placement fails)
made no difference.
* Changing anchorPoint from pole_of_inaccessibility to point_on_exterior
made no difference.
* Ruled out: NULL/empty label field values (confirmed via logs), layer
density/overlap competition (confirmed via an isolated manual test loading only
the affected features), clipping at the map item's boundary edge.
* The same .qml, loaded onto the same features in QGIS Desktop 3.28.0,
renders the callouts perfectly.
Question: Is there a known behavioral difference between QGIS 3.22 and 3.28 (or
between interactive Desktop rendering and headless/server rendering via
QgsLayoutExporter) regarding callout placement for line geometries? Or any
known issue/limitation with calloutType="simple" specifically in
non-interactive/headless rendering contexts?
Any pointers on where to look (label engine internals, GEOS version dependency,
changelog entries between 3.22 and 3.28 related to labeling/callouts, missing
processEvents() calls, etc.) would be greatly appreciated.
Thanks, Yoshimi
_______________________________________________
QGIS-Developer mailing list
[email protected]
List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
