QGIS 4 is around the corner, and it brings a big change for plugin developers: the move from Qt5 to Qt6. To get ahead of it, I spent some time making sure two of my plugins keep working on the new version. I’m happy to share that both QGIS Hub Plugin 0.6.0 and Encoded Polyline 1.0.0 are now out, and both run on QGIS 3 / Qt5 and QGIS 4 / Qt6.
QGIS Hub Plugin 0.6.0
The QGIS Hub Plugin lets you browse and fetch resources from the QGIS Hub — styles, processing models, processing scripts, 3D models, layer definitions, maps, and more — directly from inside QGIS, without hunting through a website and downloading files manually.
The QGIS Hub Plugin resource browser
The headline of this release is QGIS 4 / Qt6 support, but a number of smaller improvements landed too. Here are the highlights:
QGIS 4 / Qt6 support
- The plugin now declares
supportsQt6=Trueand works on both QGIS 3 (Qt5) and QGIS 4 (Qt6). - All Qt enum usage was migrated to the fully-scoped form (
Qt.ItemDataRole.UserRole,QSizePolicy.Policy.Minimum,QNetworkReply.NetworkError.NoError, and so on) so the same code runs on both PyQt5 and PyQt6. QRegExpwas replaced withQRegularExpression, since Qt6 dropped the former.- A Qt6 / QGIS 4 integration test job (
qgis/qgis:4.0) was added to CI, running alongside the existing Qt5 LTR job, so we catch regressions on both targets.
One quirk worth mentioning: Qt6 in QGIS 4 doesn’t ship the webp image-format plugin, so webp thumbnails wouldn’t render. To work around it, the plugin now has a Pillow-based webp thumbnail fallback (Pillow is an optional dependency).
Quality-of-life improvements
- A “Clear cache” button in the settings to wipe the cached resource list and downloaded thumbnails.
- A thumbnail download progress bar in the QGIS message bar while the resource browser is being populated for the first time.
- Uniform square-canvas icons, so list-view cells are the same size regardless of the thumbnail’s aspect ratio.
- A clearer error message when you try to add a PyQt5-only processing script on Qt6, instead of an opaque traceback.
There were also a handful of fixes — translation extraction for the new error branches, recursive file counting in the cache cleaner, and a couple of Qt6-specific UI glitches. You can read the full list in the changelog.
Encoded Polyline 1.0.0
The Encoded Polyline plugin decodes and visualizes an encoded polyline and loads it into QGIS as a memory layer. Polyline encoding is a lossy compression algorithm that stores a series of coordinates as a single string — it’s what routing services like Google Maps and Valhalla return.
The Encoded Polyline dialog
I originally built it to debug Valhalla’s routing output, because the online tools I found were limited — they couldn’t compare two polylines, hung on long lines, or couldn’t save the result. The plugin supports a custom layer name, custom precision (Google uses 5, OpenStreetMap uses 6), and ships with a few samples to play with.
Sample output: the Yogyakarta Ring Road, decoded from an encoded polyline
This 1.0.0 release marks its first stable, non-experimental version. The changes:
- QGIS 4 / Qt6 support (
qgisMaximumVersion=4.99). - Dropped the vendored
sixdependency — no longer needed now that Python 2 is long gone. - Added a GitHub Actions CI with lint, syntax check, and polyline tests.
- The packaging now bundles only the files actually needed for the plugin upload.
Why bother with QGIS 4 now?
The Qt5 → Qt6 migration is the kind of work that’s easy to put off until it breaks. But doing it early has a nice payoff: the same codebase keeps working on the current QGIS 3 LTR while being ready for QGIS 4 the day it lands. Setting up a CI matrix that tests both Qt5 and Qt6 means I get a heads-up the moment something diverges, instead of finding out from a bug report after release.
If you use either plugin, please update and let me know if anything breaks on QGIS 4. Issues and PRs are very welcome:
- QGIS Hub Plugin: https://github.com/qgis/QGIS-Hub-Plugin
- Encoded Polyline: https://github.com/ismailsunni/qgis-encoded-polyline
Fin.