Optionally exclude CJK glyphs from offline downloads

[ChrisLoer]

This is a proof-of-concept for a fix to issue #11561 -- for small offline packs, the size of the pack is dominated by the space taken up by CJK glyphs, even though many or most people won't use them:

• For maps intended for CJK audiences, we typically recommend using local CJK glyph generation, so it's not necessary to cache the glyphs in an offline pack.
• For offline maps intended for non-CJK audiences, it is likely that the offline region covers an area in which there are no or very few CJK glyphs, so there's a good chance it's OK to exclude them.

For a z1/z2 offline region of Satellite Streets, it looks like excluding CJK glyphs brings the bundle size down from ~90MB to ~12MB.

Currently the code defaults to the existing behavior of including the glyphs. We should consider defaulting to excluding the glyphs.

TODO:

• Android implementation
• Automated tests
• Documentation

cc @1ec5 @lloydsheng @kkaefer

[ChrisLoer]

@LukasPaczos For the Android implementation I didn't see any automated tests (outside of the core tests), but I just manually tested changing the value in OfflineActivity.

[ChrisLoer]

@LukasPaczos My initial Android implementation has the same issue @1ec5 noted in the iOS implementation: the addition of an extra parameter to the OfflineTilePyramidRegionDefinition and the OfflineGeometryRegionDefinition constructors isn't backwards compatible, and I don't think Java supports default argument values.

What do you think is the idiomatic way to handle this? Create a second constructor that takes the extra argument?

[1ec5]

Looks good on the iOS/macOS front. Suggested iOS/macOS changelog blurb:

Added the MGLOfflineRegion.includesIdeographicGlyphs property, which you can set to NO to exclude CJK glyphs and save space. (#13607)

[1ec5]

eb46bd8c7f6b982d308d47dd2e76be15b65816d7 fixes some Auto Layout misplaced view warnings by adding constraints to the checkbox and updating the buttons’ constraints.

[LukasPaczos]

What do you think is the idiomatic way to handle this? Create a second constructor that takes the extra argument?

Yes, the best way would be to create a second constructor with the extra argument which is called by the original constructor with the default value as the extra argument.

[ChrisLoer]

OK, I think we're good to go, thanks for the help, everybody!

~450 lines touched to add a boolean flag. 😬