Bug#25525
* lisp/textmodes/css-mode.el (css--color-map): New constant.
(css-value-class-alist): Use css--color-map.
(css--number-regexp, css--percent-regexp)
(css--number-or-percent-regexp, css--angle-regexp): New constants.
(css--color-skip-blanks, css--rgb-color, css--hsl-color): New
functions.
(css--colors-regexp): New constant.
(css--hex-color, css--named-color, css--compute-color)
(css--contrasty-color, css--fontify-colors)
(css--fontify-region): New functions.
(css-mode): Set font-lock-fontify-region-function.
(css-mode-syntax-table): Set syntax on more characters.
(css-fontify-colors): New defcustom.
(scss-mode-syntax-table): Define syntax for ?$ and ?%.
* test/lisp/textmodes/css-mode-tests.el (css-test-property-values):
Update.
(css-test-rgb-parser, css-test-hsl-parser)
(css-test-named-color): New tests.
* etc/NEWS: Add entry.
* etc/NEWS: Mention new feature.
* lisp/textmodes/css-mode.el (css-mode-map): New defvar.
(css--mdn-lookup-history): New defvar.
(css-lookup-url-format): New defcustom.
(css--mdn-property-regexp, css--mdn-completion-list): New defconsts.
(css--mdn-after-render, css--mdn-find-symbol, css-lookup-symbol): New
defuns.
* test/lisp/textmodes/css-mode-tests.el (css-mdn-symbol-guessing): New
test.
* test/lisp/textmodes/css-mode-tests.el
(css-test-foreign-completions): New test for
`css--foreign-completions'.
(css-test-complete-selector-tag): Rename test.
(css-test-complete-selector-class): New test testing completion of
class names in selectors.
(css-test-complete-selector-id): New test testing completion of IDs in
selectors.
* lisp/textmodes/css-mode.el (css--complete-property-value): Make
"initial" and "unset" completion candidates for all CSS properties,
just like "inherit".
* test/lisp/textmodes/css-mode-tests.el
(css-test-complete-property-value): Update test to reflect the above
change.
* lisp/textmodes/css-mode.el (css-value-class-alist): Add `calc()' as
a completion candidate for several value classes.
(css--value-class-lookup): Return only unique results.
* test/lisp/textmodes/css-mode-tests.el
(css-test-property-values-no-duplicates)
(css-test-value-class-lookup): Update to reflect the above changes.
* lisp/textmodes/css-mode.el (css--property-values): Don't return
duplicate values.
* test/lisp/textmodes/css-mode-tests.el (css-test-property-values):
Take the above into account.
(css-test-property-values-no-duplicates): Test that duplicates aren't
returned by `css--property-values'.
* lisp/textmodes/css-mode.el (css--property-values): Cache computed
values.
* test/lisp/textmodes/css-mode-tests.el (css-test-property-value-cache):
New regression test for the above.
* lisp/textmodes/css-mode.el (css-property-alist): New defconst
holding CSS identifiers and the values they can have.
(css-property-ids): Compute dynamically from `css-property-alist'.
(css-value-class-alist): New defconst holding property value classes
and their values.
(css--property-value-cache): New variable providing a cache for
`css--property-values'.
(css--value-class-lookup): New function for computing a list of values
in a value class.
(css--property-values): New function for computing a list of possible
values for a CSS property.
(css--complete-property-value): New function for completing a property
value.
(css-completion-at-point): Add support for completing property values.
* test/lisp/textmodes/css-mode-tests.el: New file.
