Add support for letter spacing of text

[nvkelso]

This issue is a followup to tangrams/refill-style#69.

Refill and other Mapzen basemap styles use a poor man's approach (name.split('').join(' ');) to letter-spacing aka tracking for labels of continent, ocean, and sea that fails with complex non-Latin scripts. Rather than the existing hackery, we'd like to support letter-spacing as a top-level text feature and suspect Tangram JS can leverage the existing CSS letter-spacing feature for parity.

NOTE: kerning is a related concept but refers more to the space between specific combinations of characters.

Screenshots from @tallytalwar's original issue:

[bcamper]

I don't believe that canvas text supports the letter spacing concept (it is a separate text rendering implementation than CSS unfortunately), which makes this more difficult. Let me do some research on this and possible alternatives.

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On Tue, Sep 12, 2017 at 4:52 AM Nathaniel V. KELSO ***@***.***> wrote: This issue is a followup to tangrams/refill-style#69 <tangrams/refill-style#69>. Refill and other Mapzen basemap styles use a poor man's approach (name.split('').join(' ');) to letter-spacing aka tracking <https://en.wikipedia.org/wiki/Letter-spacing> for labels of continent, ocean, and sea that fails with complex non-Latin scripts. Rather than the existing hackery, we'd like to support letter-spacing as a top-level text feature and suspect Tangram JS can leverage the existing CSS letter-spacing feature for parity. *NOTE: kerning <https://en.wikipedia.org/wiki/Kerning> is a related concept but refers more to the space between specific combinations of characters.* Screenshots from @tallytalwar <https://github.com/tallytalwar>'s original issue: [image: screen shot 2017-08-30 at 4 36 21 pm] <https://user-images.githubusercontent.com/360641/29900806-dc15806e-8da8-11e7-9a00-604b4f69ca31.png> [image: screen shot 2017-08-30 at 4 36 01 pm] <https://user-images.githubusercontent.com/360641/29900805-dc152772-8da8-11e7-8e0c-9d59404cc23a.png> [image: screen shot 2017-08-30 at 12 57 56 pm] <https://user-images.githubusercontent.com/360641/29900807-dc1c8a9e-8da8-11e7-8003-1d3285b2f2bf.png> [image: screen shot 2017-08-30 at 12 57 24 pm] <https://user-images.githubusercontent.com/360641/29900809-dc34eaee-8da8-11e7-825e-c9cbb1c14e0a.png> [image: screen shot 2017-08-30 at 12 55 02 pm] <https://user-images.githubusercontent.com/360641/29900808-dc1cc716-8da8-11e7-8584-85572c5467a3.png> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1646>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABBXbP_oIzohkhm5vZ_qNgEzDOm51bpks5shY92gaJpZM4PTrt7> .

[tallytalwar]

Some probably discussions on letter-spacing which we might be helpful here to come to a consensus on the implementation of this feature :

harfbuzz/harfbuzz#64
http://typedrawers.com/discussion/1816/cursive-attachment-for-latin
harfbuzz/harfbuzz#358
harfbuzz/harfbuzz#224