Enable webgl1 fallback

[birkskyum]

This is a fix to the regression caused by the complete sunset of webgl1. Closes #2653 , Closes #2644

This reverts shaders to GL ES 1.0, and adds conditional logic and union typings to allow webgl1 as a fallback while keeping the majority of users on webgl2.

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 78.43137% with 11 lines in your changes missing coverage. Please review.

Project coverage is 73.77%. Comparing base (3ab0fcd) to head (dda0428).
Report is 1694 commits behind head on main.

Files with missing lines	Patch %	Lines
src/gl/context.ts	65.38%	9 Missing ⚠️
src/gl/value.ts	80.00%	1 Missing ⚠️
src/util/webp_supported.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2656      +/-   ##
==========================================
- Coverage   73.83%   73.77%   -0.07%     
==========================================
  Files         237      238       +1     
  Lines       18893    18925      +32     
  Branches     4223     4244      +21     
==========================================
+ Hits        13949    13961      +12     
- Misses       4944     4964      +20     

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[HarelM]

Is there a way to keep the new shaders code and use the rollup to translate it to "old" code?
So that if and when we move to the new shaders we would only need to remove this part?
This is a rough thought, I don't know how possible it is.

[birkskyum]

Is there a way to keep the new shaders code and use the rollup to translate it to "old" code? So that if and when we move to the new shaders we would only need to remove this part? This is a rough thought, I don't know how possible it is.

I've made a webgl1 compatibility solution to the generate-shaders that downgrades the shaders. More advanced features of webgl2, and refactor of associated logic, won't be possible to approach with this webgl1 limitation in place, but at least the changes we have done already can be kept.

[HarelM]

LGTM! Thanks! Yea, this is what I meant.

[handymenny]

the downgrade is done at build time, right? what about downgrading at runtime? Indeed that would be a (small?) penality for webgl1 users, but it clearly states that webgl2 is the path that maplibre is optimizing for.

[birkskyum]

@handymenny , yes, this is done a build time. It's an interesting idea to consider runtime transpiring - i'll bring that suggestion to the tsc meeting discussion as well.