Add QGIS 4.x (Qt6) support while keeping QGIS 3.22+ compatibility

[samhashemi]

Manual testing plan — ✅ complete on both QGIS 3.x and QGIS 4

Verified on a QGIS 3.4x install (Qt5) and a QGIS 4.0+ install (Qt6), with the f62f2c1 build:

• QGIS 3.x — all steps verified by @makella (results)
• QGIS 4.0+ — all steps verified by @makella (results): install, menu/toolbar, sign-in, map creation with categorized/graduated/heatmap vector layers + raster, upload + Open Map, styling fidelity on the Felt side, recent maps, workspaces, log out/re-login, clean Python console.
• Raster color-ramp question from part 1 confirmed not a regression — main and this branch produce byte-identical raster FSL for all supported renderer types (details). Pre-existing behavior, to be filed as a separate issue.

Earlier manual testing on QGIS 4 caught two Qt6-only bugs the unit suite can't reach — an endless repaint loop when opening the dialog (Qt.transparent, fixed in 84fea26) and every upload failing (QByteArray.append(str), fixed in f62f2c1). A follow-up audit (static sweep for all known PyQt6 behavior changes + scripted render/click probes of every GUI component inside a QGIS 4.0.3 container) found no further issues, and a regression test now covers the upload request builder.

Original step-by-step test plan (for future releases)

1. Install: install the built zip via Plugins → Manage and Install Plugins → Install from ZIP. Loads with no Python errors, not flagged incompatible.
2. Menu/toolbar: Web → Add to Felt menu and the Share Map to Felt toolbar button appear.
3. Sign in: authorize dialog renders, browser OAuth completes, dialog reflects the signed-in account.
4. Create a map: from a project with a few vector layers (include categorized, graduated and heatmap styling) plus a raster layer, run Add to Felt. Progress bar advances, upload completes, Open Map opens the map in the browser.
5. Styling fidelity: on the resulting Felt map, the heatmap gradient and vector colors/line styles match QGIS.
6. Recent maps: the dialog's recent maps list shows thumbnails, hover/selection works, picking an existing map works.
7. Workspaces: the workspace dropdown populates and switching updates the recent maps list.
8. Log out / re-login: Log Out from the settings menu works; signing back in works.
9. No new warnings/exceptions in the QGIS Python console / message log throughout.

Summary

QGIS 4.0 is Qt6/PyQt6-based and breaks plugins that use unscoped Qt enums or removed Qt5 APIs. This PR updates the plugin so a single codebase runs on everything from QGIS 3.22 through QGIS 4.x, and marks it "QGIS 4 ready" in the plugin repository.

Code changes

• Fully scoped Qt enums (~190 call sites): Qt.UserRole → Qt.ItemDataRole.UserRole, Qt.NoPen → Qt.PenStyle.NoPen, QDialogButtonBox.Ok → QDialogButtonBox.StandardButton.Ok, etc. — including the lowercase Qt.GlobalColor members (Qt.transparent → Qt.GlobalColor.transparent) used in paint paths. The scoped forms work identically on PyQt5 and PyQt6. QGIS API enums (QgsUnitTypes.RenderPoints, QgsWkbTypes.Point, …) are unchanged — verified by introspection in a QGIS 4.0.3 container that the QGIS 4 bindings still support unscoped access for those.
• Removed Qt5 APIs / behaviors: QFontMetrics.width() → horizontalAdvance(), dialog exec_() → exec(), QSvgWidget imported from QtSvgWidgets on Qt6 builds (with a fallback for QGIS 4.0.x, which doesn't wrap that module in qgis.PyQt yet), the one direct PyQt5 import now goes through qgis.PyQt, and the multipart upload body is built as bytes instead of QByteArray.append(str), which PyQt6 rejects.
• metadata.txt: added qgisMaximumVersion=4.99 (what lists the plugin as QGIS 4 compatible — the old supportsQt6 flag is deprecated) and bumped the version to 1.1.0.

Test/CI changes

• New unit test for create_upload_file_request (the multipart upload body builder) — previously only covered behind a live auth token, which is how the Qt6 upload bug slipped past CI.
• The heatmap FSL conversion test now has Qt-version-aware expected colors: Qt6 rounds gradient interpolation slightly differently (e.g. #c3c3c3 vs #c4c4c4), and the converter output is correct on both.
• test_suite.py now creates the QgsApplication before test discovery (on Qt6, widgets created at module import crash without an application instance), passes an explicit top_level_dir (required on newer Python for the test modules' relative imports), and adds a run_tests_and_exit() entry point that reports failures via exit code without running interpreter teardown (exiting a headless QgsApplication can segfault on Qt6, which would mask the result).
• The test workflow matrix is now QGIS 3.22, 3.34, 3.40 LTR, 3.44 LTR and 4.0. Tests run headless via QT_QPA_PLATFORM=offscreen because the newer official Docker images never execute qgis --code scripts non-interactively (the old qgis_testrunner.sh flow hangs on them).

Verification

Full suite (69 tests) passes with the exact CI command in qgis/qgis:release-3_22 (Qt5), ltr/3.44 (Qt5) and 4.0/4.0.3 (Qt6) Docker images; flake8, pycodestyle and pylint clean/at baseline. CI is green across the whole matrix.

Note: this overlaps with the update-for-qgis4 branch from March — this PR additionally keeps QGIS 3.22 compatibility, so users on older QGIS continue to get updates.

https://claude.ai/code/session_01LCTq6nNRJEWyBGQ1sjipHw

---

Generated by Claude Code

[github-actions]

Plugin ready!

A test version of this PR is available for testing here.

(Built from commit f62f2c1)

[makella]

Test plan part 1: 3.22+ compatibility

@samhashemi went through the first part since i had 3.4... installed already. to finish this test i need to try the raster styling step again with the last released plugin to make sure that it isn't a regression - see step 5 below.

then i'll do part 2 with the newer version of QGIS!

Testing with commit f62f2c1 zip download as the latest.

On QGIS 3.x

• 1. Install: install the built zip via Plugins → Manage and Install Plugins → Install from ZIP. Loads with no Python errors, not flagged incompatible.

• 2. Menu/toolbar: Web → Add to Felt menu and the Share Map to Felt toolbar button appear.

• 3. Sign in: authorize dialog renders, browser OAuth completes, dialog reflects the signed-in account.

• 4. Create a map rom a project with a few vector layers (include categorized, graduated and heatmap styling) plus a raster layer,

• run Add to Felt. Progress bar advances, upload completes, Open Map opens the map in the browser.

• 5. Styling fidelity: on the resulting Felt map, the heatmap gradient and vector colors/line styles match QGIS (exercises the FSL conversion paths touched here).

  • resulting map - @samhashemi here i need to check why the raster styling didn't carry through... i will try the previous plugin to see if it does before determining if this is a regression. it is coming in as an image instead of color range. all other styles ARE preserved.

• 6. Recent maps: the dialog's recent maps list shows thumbnails, hover/selection works, picking an existing map works.

• 7. Workspaces: the workspace dropdown populates and switching updates the recent maps list.

• 8. Log out / re-login: Log Out from the settings menu works; signing back in works.
• 9. No new warnings/exceptions in the QGIS Python console / message log throughout.

[samhashemi]

@makella thanks for the thorough run-through! On the step 5 raster question — it's not a regression from this PR, so no need to re-test with the previous plugin release unless you want to confirm independently.

To verify, I ran an A/B comparison inside a QGIS 3.44 container: the same DEM raster styled with each supported renderer (singleband pseudocolor interpolated/discrete/exact, singleband gray, paletted), converted to FSL by this branch and by main. The output is byte-for-byte identical, and all five renderer types produce proper FSL color ramps on both versions. This PR's changes to the raster path are pure enum-scoping with no logic change.

What likely happened instead: the plugin only converts single-band renderers to Felt color-ramp styling. If a raster uses anything else (multiband RGB, hillshade, contrast-enhancement-only defaults, etc.), raster_renderer_to_fsl returns nothing and the plugin intentionally falls back to uploading a styled image — behavior that's the same on main. Worth checking which renderer the layer panel shows for that raster (Symbology → Render type); if it's "Singleband pseudocolor" and it still came through as an image, that would be a pre-existing bug worth its own issue rather than part of this PR.

https://claude.ai/code/session_01LCTq6nNRJEWyBGQ1sjipHw

---

Generated by Claude Code

[makella]

Test plan part 2: QGIS 4.0+

• 1. Install: install the built zip via Plugins → Manage and Install Plugins → Install from ZIP. Loads with no Python errors, not flagged incompatible.

• 2. Menu/toolbar: Web → Add to Felt menu and the Share Map to Felt toolbar button appear.

• 3. Sign in: authorize dialog renders, browser OAuth completes, dialog reflects the signed-in account.

• 5. Create a map from a project with a few vector layers (include categorized, graduated and heatmap styling) plus a raster layer

• run Add to Felt. Progress bar advances,

• upload completes, Open Map opens the map in the browser.

• 6. Styling fidelity: on the resulting Felt map, the heatmap gradient and vector colors/line styles match QGIS (exercises the FSL conversion paths touched here).

  • map link
  • @samhashemi yes seems to be that the raster is a different issue that we can file separately

• 7. Recent maps: the dialog's recent maps list shows thumbnails, hover/selection works, picking an existing map works.

• 8. Workspaces: the workspace dropdown populates and switching updates the recent maps list.

• 9. Log out / re-login: Log Out from the settings menu works; signing back in works.
• 10. No new warnings/exceptions in the QGIS Python console / message log throughout.

[makella]

ran through test plan on qgis 3.42.1 and 4.0.3 both check out and pass. as noted in the comments, there may be a raster rendering fix and/or bug if symbolized with singleband pseudocolor but that is outside the scope of this PR.