Fixing tiles resolutions

[rldhont]

fixes #4332

Currently, if the map allows you to go beyond the min/zoom resolution of a WMTS or XYZ source, Lizmap won't display anything beyond this min/zoom resolution.

OpenLayers is able to do resampling. This can be seen when you zoom in progressively. OpenLayers must be forced to use the max zoom of the grid even when the user goes beyond it.

The solution is described on stackoverflow https://stackoverflow.com/questions/43538345/how-to-force-load-tiles-for-lower-resolution and is based on TileGrid's getZForResolution method https://github.com/openlayers/openlayers/blob/main/src/ol/tilegrid/TileGrid.js#L634

  getZForResolution(resolution, opt_direction) {
    const z = linearFindNearest(
      this.resolutions_,
      resolution,
      opt_direction || 0,
    );
    return clamp(z, this.minZoom, this.maxZoom);
  }

This method is based on the this.resolutions_ list of grid resolutions. The index of the resolution closest to that in parameter is then set to the min or max zoom value.

So if this.resolutions_ contains 24 values but maxZoom is 19, then when the map is at levels 20, 21, 22, 23 and 24, the grid will limit queries to zoom 19.

Funded by FM Projet

[3liz-bot]

The backport to release_3_7 failed:

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

stderr

error: could not apply db21ff0da... Fixing tiles resolutions
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".
hint: Disable this message with "git config advice.mergeConflict false"

stdout

Auto-merging assets/src/modules/config/BaseLayer.js
CONFLICT (modify/delete): assets/src/modules/map.js deleted in HEAD and modified in db21ff0da (Fixing tiles resolutions).  Version db21ff0da (Fixing tiles resolutions) of assets/src/modules/map.js left in tree.

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_7 release_3_7
# Navigate to the new working tree
cd .worktrees/backport-release_3_7
# Create a new branch
git switch --create backport-4627-to-release_3_7
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick db21ff0da4b461a77d48f6a34961fc8c5976dedc,f2b6acb07a94a325785f02d150d4e429786d1064,9c0fa34da4589f744a87f7c09947c22bba7ffd69,0a7cd196f9276036d30f6681e8fd570c6de6e38d,30e65c63713b8cc4dfa9c3db47736eaa36943c38
# Push it to GitHub
git push --set-upstream origin backport-4627-to-release_3_7
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release_3_7

Then, create a pull request where the base branch is release_3_7 and the compare/head branch is backport-4627-to-release_3_7.