[geometry snapper] Fix wrong point-to-segment distance within maths

[nirvn]

Description

This PR fixes a pretty serious issue with our QgsGeometrySnapper class whereas snapping of point geometry to line segments would often fail due to a bogus distance to line calculation.

We were checking whether a given tolerance/distance was within a squared distance value, leading to failures 😱

Fixes #56424 , #50121 , and likely other issues. A test has been added.

[github-actions]

🪟 Windows builds ready!

Windows builds of this PR are available for testing here. Debug symbols for this build are available here.

(Built from commit bc957d6)

[nirvn]

@nyalldawson , addressed.

[github-actions]

Tests failed for Qt 6

One or more tests failed using the build from commit bc957d6

composermap_render (render)

composermap_render

Test failed at render at tests/src/core/testqgslayoutmap.cpp:185

Rendered image did not match tests/testdata/control_images/composer_map/expected_composermap_render/expected_composermap_render.png (found 13824 pixels different)

composermap_overview_center (overviewMapCenter)

composermap_overview_center

Test failed at overviewMapCenter at tests/src/core/testqgslayoutmapoverview.cpp:224

Rendered image did not match tests/testdata/control_images/composer_mapoverview/expected_composermap_overview_center/expected_composermap_overview_center.png (found 116 pixels different)

flat_terrain_2 (testFlatTerrain)

flat_terrain_2

Test failed at testFlatTerrain at tests/src/3d/testqgs3drendering.cpp:316

Rendered image did not match tests/testdata/control_images/3d/expected_flat_terrain_2/expected_flat_terrain_2.png (found 2725 pixels different)

dem_terrain_1 (testDemTerrain)

dem_terrain_1

Test failed at testDemTerrain at tests/src/3d/testqgs3drendering.cpp:363

Rendered image did not match tests/testdata/control_images/3d/expected_dem_terrain_1/expected_dem_terrain_1.png (found 1603 pixels different)

4978_line_rendering_2 (testEpsg4978LineRendering)

4978_line_rendering_2

Test failed at testEpsg4978LineRendering at tests/src/3d/testqgs3drendering.cpp:1293

Rendered image did not match tests/testdata/control_images/3d/expected_4978_line_rendering_2/expected_4978_line_rendering_2.png (found 128045 pixels different)

phong_shading (testPhongShading)

phong_shading

Test failed at testPhongShading at tests/src/3d/testqgs3drendering.cpp:503

Rendered image did not match tests/testdata/control_images/3d/expected_phong_shading/expected_phong_shading.png (found 55 pixels different)

metal_rough (testExtrudedPolygonsMetalRoughShading)

metal_rough

Test failed at testExtrudedPolygonsMetalRoughShading at tests/src/3d/testqgs3drendering.cpp:649

Rendered image did not match tests/testdata/control_images/3d/expected_metal_rough/expected_metal_rough.png (found 54 pixels different)

line_rendering_2 (testLineRendering)

line_rendering_2

Test failed at testLineRendering at tests/src/3d/testqgs3drendering.cpp:761

• Rendered image did not match tests/testdata/control_images/3d/expected_line_rendering_2/default/expected_line_rendering_2.png (found 5180 pixels different)
• Rendered image did not match tests/testdata/control_images/3d/expected_line_rendering_2/travis/expected_line_rendering_2.png (found 43 pixels different)

dem_terrain_filtered_1 (testFilteredDemTerrain)

dem_terrain_filtered_1

Test failed at testFilteredDemTerrain at tests/src/3d/testqgs3drendering.cpp:1370

Rendered image did not match tests/testdata/control_images/3d/expected_dem_terrain_filtered_1/expected_dem_terrain_filtered_1.png (found 3886 pixels different)

composermap_overview_center

composermap_overview_center

Test failed at testOverviewMapCenter at tests/src/python/test_qgslayoutmapoverview.py:161

Rendered image did not match tests/testdata/control_images/composer_mapoverview/expected_composermap_overview_center/expected_composermap_overview_center.png (found 116 pixels different)

composermap_overview_belowmap

composermap_overview_belowmap

Test failed at testOverviewStacking at tests/src/python/test_qgslayoutmapoverview.py:333

Rendered image did not match tests/testdata/control_images/composer_mapoverview/expected_composermap_overview_belowmap/expected_composermap_overview_belowmap.png (found 580 pixels different)

The full test report (included comparison of rendered vs expected images) can be found here.

Further documentation on the QGIS test infrastructure can be found in the Developer's Guide.

[nyalldawson]

Unrelated test failures

[qgis-bot]

The backport to release-3_34 failed:

The process '/usr/bin/git' failed with exit code 1

stderr

error: could not apply bc957d68b00... Address review
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".

stdout

Auto-merging src/analysis/vector/qgsgeometrysnapper.cpp
Auto-merging src/analysis/vector/qgsgeometrysnapper.h
[backport-56426-to-release-3_34 f60f3103028] [geometry snapper] Fix wrong point-to-segment distance within maths
 Author: Mathieu Pellerin <nirvn.asia@gmail.com>
 Date: Tue Feb 20 20:27:45 2024 +0700
 3 files changed, 10 insertions(+), 5 deletions(-)
Auto-merging src/analysis/vector/qgsgeometrysnapper.cpp
CONFLICT (content): Merge conflict in src/analysis/vector/qgsgeometrysnapper.cpp
Auto-merging src/analysis/vector/qgsgeometrysnapper.h

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-release-3_34 release-3_34
# Navigate to the new working tree
cd .worktrees/backport-release-3_34
# Create a new branch
git switch --create backport-56426-to-release-3_34
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick b1d22b9e0a6e8a2fe6c393817fb1319de44d9a21,bc957d68b004c078a163e315d292fdc548edccdd
# Push it to GitHub
git push --set-upstream origin backport-56426-to-release-3_34
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-3_34

Then, create a pull request where the base branch is release-3_34 and the compare/head branch is backport-56426-to-release-3_34.