Project: Document supported missing CSS properties

[estelle]

Problem statement

Some CSS properties are supported by one or more browsers, but are neither documented on MDN nor are they in the webdocs backlog.

Proposed solutions

1. Add these properties to BCD so they appear in https://openwebdocs.github.io/web-docs-backlog/
2. Document these missing properties if appropriate

(There are additional properties supported by browsers NOT in the backlog. This project does not address those).

Task list

• buffered-rendering ({svg.global_attributes,css.properties}.{buffered-rendering,color-rendering} - missing mdn/browser-compat-data#24053)
• color-rendering ({svg.global_attributes,css.properties}.{buffered-rendering,color-rendering} - missing mdn/browser-compat-data#24053)
• glyph-orientation-horizontal (css.properties.glyph-orientation-horizontal - missing mdn/browser-compat-data#24052)
• mask-position-x (-webkit-mask-position-x documented, but un-prefixed version exists in Safari TP)
• mask-position-y (-webkit-mask-position-y documented, but un-prefixed version exists in Safari TP)
• text-box-edge (https://caniuse.com/?search=text-box-edge, exists in Safari TP)
• text-box-trim (https://caniuse.com/?search=text-box-trim, exists in Safari TP)

Possibly:

• moz-window-dragging

More information

See mdn/content#35108. That PR is closed as it is not intended to be merged. It contains a list of all the longhand CSS properties supported in FF, Chrome, Edge, and Safari at the time of the PR's writing.

[estelle]

From the issues brought up in the CSS longhand properties PR, this issue addresses the following properties:

• buffered-rendering
• color-rendering
• glyph-orientation-horizontal
• mask-position-x
• mask-position-y
• text-box-edge
• text-box-trim

Approx. 30 properties are addressed by CSS missing baseline properties project

At least ten additional properties are supported by at least one browser but are missing documentation, including the following. These ARE in the backlog of missing properties so aren't tracked by this issue:

• alignment-baseline
• alt
• app-region
• baseline-shift
• baseline-source
• glyph-orientation-vertical
• ime-mode
• object-view-box
• speak
• view-transition-class