Fix camera jumps with terrain and transformCameraUpdate.

[chrneumann]

Fixes camera jumps at end of movement when terrain and transformCameraUpdate is enabled (fixes #4233).

Had to enable WebGL for headless Chrome, as I could not reproduce the bug without it in headless mode.
The problem was caused by directly accessing the map's transform, instead of using _getTransformForUpdate and _applyUpdatedTransform.

Launch Checklist

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
• Include before/after visuals or gifs if this PR includes visual changes.
• Write tests for all new functionality.
• Document any changes to public APIs.
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• Add an entry to CHANGELOG.md under the ## main section.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 88.12%. Comparing base (b5a3159) to head (9a7eb89).
Report is 5 commits behind head on main.

Files	Patch %	Lines
src/ui/handler_manager.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4299      +/-   ##
==========================================
+ Coverage   87.87%   88.12%   +0.25%     
==========================================
  Files         246      246              
  Lines       33372    33375       +3     
  Branches     2194     2189       -5     
==========================================
+ Hits        29325    29413      +88     
+ Misses       3050     2969      -81     
+ Partials      997      993       -4     

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[chrneumann]

The last commit should fix it. Thanks to @UberMouse for the hint at #4377 (comment)

[HarelM]

Thanks for taking the time to fix this issue!
This looks like the right solution to the problem.
See my small comments above.

[HarelM]

I think the following unit test can reproduce this issue to some extent - as the recalculate zoom will be done on the original transform and won't take the zoom changes that are done as part of the transfrom camera update:

    test('recalculate zoom is done on the camera update transform', () => {
        const map = createMap({
            interactive: true, 
            clickTolerance: 4,
            transformCameraUpdate: ({zoom}) => ({ zoom: zoom + 0.1})
        });
        map.terrain = {
            pointCoordinate: () => null,
            getElevationForLngLatZoom: () => 1000
        } as any;
        const canvas = map.getCanvas();
        simulate.dragWithMove(canvas, {x: 100, y: 100}, {x: 100, y: 150});
        map._renderTaskQueue.run();

        expect(map.getZoom()).toBe(0.20008255564976615);
    });

What do you think?

[chrneumann]

Seems fine, still I think an integration test that involves transformCameraUpdate wouldn't be bad. But fine for me :)

[HarelM]

I'm good with both tests, just please simplify the style in the integration test...

[chrneumann]

I'm good with both tests, just please simplify the style in the integration test...

Ah, I did that on purpose. Thought about simplifying it, which would be fine for the automatic testing, but if you want to observe the bug, the more complete style is really helpful. But yeah, I can simplify it if you don't think thats important.

[HarelM]

Yeah, the test should be as simple as possible, for debugging you can change the examples in order to reproduce an issue.
Please add the test I sent and simplify the integration test and I'll merge this PR.
Thanks!!

[chrneumann]

I think the following unit test can reproduce this issue to some extent - as the recalculate zoom will be done on the original transform and won't take the zoom changes that are done as part of the transfrom camera update:
What do you think?

Ah, you did not actually test it? At least, it never fails for me.

[HarelM]

I've test it with and without the fix and it gave different results.

[chrneumann]

Maybe I'm missing something. I pushed your unit test, you can check it with the commit "04278f129 | Fix terrain jumps with transformCameraUpdate (#4233)" reversed, which lets the integration test fail for me but not the unit test.

[chrneumann]

Ah, it fails when the fix is applied? Did you calculate the zoom by hand? Or is it fine to just fix the expected zoom value with the fix applied?

[HarelM]

Must have written the test when I removed the fix, sorry...