Add Horizontal Element Alignment [XELA] axis

[simoncozens]

Requirements

• [x] I have inspected the current Axis Registry and there is not a registered custom axis that could be used for the variation purpose on the upcoming font project.
• [x] The metadata fields of the proposed axis meet the Axis Requirements as specified in the Protocol (linked above).

Font project(s) using the axis

SixtyFour Color (to be renamed) at https://github.com/jenskutilek/homecomputer-fonts

Short description of what the axis does

As a parallel to Vertical Element Alignment [YELA], this controls the position of horizontal elements.

Image

Why is the axis needed

As the counterpart to YELA.

Axis metadata fields

(Remove this line and fill out the mock of the data structure of the axis)

#YELA based on [Wavefont](https://github.com/dy/wavefont)
tag: "XELA"
display_name: "Horizontal Element Alignment"
min_value: -100
default_value: 0
max_value: 100
precision: 0
fallback {
  name: "Default"
  value: 0
}
fallback_only: false
description:
  "Align glyphs from their default position (0%),"
  " usually the baseline, to a rightmost (100%)"
  " or leftmost (-100%) position."

[vv-monsalve]

Could this be the same XALN #126?

[simoncozens]

I don't think so. XALN aligns the entire glyph, YELA (and proposed XELA) aligns an element of the glyph.

[vv-monsalve]

Revised description would be

description:
  "Align glyph elements from their default position (0%),"
  " usually the baseline, to a rightmost (100%)"
  " or leftmost (-100%) position."

[vv-monsalve]

Revised definitions on January 26:

Precision value could be -1 to allow the fine control and 1000 positions

#XELA based on [Sixtyfour Convergence](https://github.com/jenskutilek/homecomputer-fonts/tree/master/Sixtyfour)
tag: "XELA"
display_name: "Horizontal Element Alignment"
min_value: -100.0
default_value: 0
max_value: 100.0
precision: -1
fallback {
  name: "Default"
  value: 0
}
fallback_only: false
description:
  "Align glyph elements from their default position (0%),"
  " usually the baseline, to a rightmost (100%)"
  " or leftmost (-100%) position."