fix refinement crash when face has more than 4 vertices

[vcloarec]

fix #50541
The issue comes from that refinement of faces with vertices count greater than 4 is not allowed.

Also change the UI to not purpose to refine face if its vertices count is greater than 4.

Thanks @uclaros for your tries and to have report it!

[uclaros]

Wouldn't it be useful if refinement would still work on more than four vertices faces but with a different logic?
Once you delete a few edges and end up with a face with more than 4 vertices it is not very easy to re-create triangles: You need to completely remove the face, then select the vertices that surround the hole and do right-click -> Delaunay Triangulation

This could be handled in one step by refine face, when there are more than 4 vertices.

[vcloarec]

good point @uclaros, again !
I understand the difficulties but with the logic of this refinement, it could quite complex to handle faces with more than 4 vertices.
What needed here could be to purpose another command to triangulate faces with more than 3 vertices, this will be a new feature.

[uclaros]

What needed here could be to purpose another command to triangulate faces with more than 3 vertices, this will be a new feature.

This is what I meant, this new command could still be triggered by the same Refine Face action. If there are less than 4 vertices, use the old refinement logic. If there are more than 4, use the new triangulate logic.

[vcloarec]

this new command could still be triggered by the same Refine Face action

not sure, it will not exactly a refinement but a triangulation, not exactly the same. This refinement consists of adding new vertices in middle of edges. Triangulation, there i no more vertices, only a triangulation of a polygon. This is not exactly the same operation.

[uclaros]

OK, still the two actions could occupy the same position in the context menu and only one of them visible at a time, depending on number of vertices.

[vcloarec]

Yes, when this new action will be implemented, this action will replace the refinement action if the current face has more than 4 vertices.
If there are more than one faces selected, that will depends on the vertices count of each faces:

• If no faces with more than 4 vertices: only refinement,
• If no face with less than 5 vertices: only triangulation,
• if both:refinement and triangulation.

But it is another story, and I think it could a be a new feature PR in the future.

[uclaros]

Lgtm

[qgis-bot]

The backport to release-3_22 failed:

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

stderr

error: could not apply f982262b83... fix refinment crash when face has more than 4 vertices
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/app/mesh/qgsmaptooleditmeshframe.cpp
CONFLICT (content): Merge conflict in src/app/mesh/qgsmaptooleditmeshframe.cpp
Auto-merging src/app/mesh/qgsmaptooleditmeshframe.h
Auto-merging src/core/mesh/qgsmeshadvancedediting.cpp
Auto-merging tests/src/core/testqgsmesheditor.cpp

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_22 release-3_22
# Navigate to the new working tree
cd .worktrees/backport-release-3_22
# Create a new branch
git switch --create backport-50556-to-release-3_22
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick f982262b8373bd71c061b044cff1ea49258a3bf5,67a365be13fd39cc21450117eb0799658034d754
# Push it to GitHub
git push --set-upstream origin backport-50556-to-release-3_22
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-3_22

Then, create a pull request where the base branch is release-3_22 and the compare/head branch is backport-50556-to-release-3_22.