Proposed improvement: text metrics interface

[KaliedaRik]

Issue:
SC's current Phrase entity text handling is fairly rudimentary. While words and glyphs can be styled individually, and SC does what it can to support multiline Phrases, glyph positioning deliberately ignores textBaseline considerations and forces the baseline to the top. This is good when we are treating the Phrase's text content as a single graphic, but limits the mixing of different fonts and font sizing within a single Phrase.

Investigation:
The Canvas API's TextMetrics interface has improved over the years and some of its key metrics (around actualBoundingBox) are widely supported. However:

• fontBoundingBox attributes are not supported in Firefox
• baseline and other metrics are only supported in Safari

While improved baseline support is probably out of scope for SC at this time, there may be an opportunity for better, more accurate line height support which can be introduced sooner rather than later

Risks:
Text and font support in the canvas remain a nightmare. Direct interactive canvas text will never be in-scope for SC, which must never become a replacement for existing DOM/CSS text layout/interaction functionality.

[KaliedaRik]

Currently in development for the new Label and EnhancedLabel entitys, which will replace Phrase entitys in v8.13.0

[KaliedaRik]

This work has been completed in PR #75 and merged into v8-dev

[KaliedaRik]

Released as part of v8.13.0. Marking discussion as completed.