Add command for cycling between CSS color formats

* lisp/textmodes/css-mode.el (css-mode-map): Add keybinding for
'css-cycle-color-format'.
(css--rgb-color): Add support for extracting alpha component.
(css--hex-alpha, css--color-to-4-dpc, css--named-color-to-hex)
(css--format-rgba-alpha, css--hex-to-rgb)
(css--rgb-to-named-color-or-hex): New functions.
(css-cycle-color-format): New command for cycling between color
formats.

* test/lisp/textmodes/css-mode-tests.el (css-test-color-to-4-dpc):
(css-test-named-color-to-hex, css-test-format-rgba-alpha)
(css-test-hex-to-rgb, css-test-rgb-to-named-color-or-hex)
(css-test-cycle-color-format, css-test-hex-alpha): New tests for the
changes mentioned above.

* etc/NEWS: Mention the new command.

1 files changed, 73 insertions, 0 deletions

diff --git a/test/lisp/textmodes/css-mode-tests.el b/test/lisp/textmodes/css-mode-tests.el
index 1e58751f140..2be57726256 100644
--- a/test/lisp/textmodes/css-mode-tests.el
+++ b/test/lisp/textmodes/css-mode-tests.el
@@ -244,6 +244,73 @@
       (should (member "body" completions))
       (should-not (member "article" completions)))))
 
+(ert-deftest css-test-color-to-4-dpc ()
+  (should (equal (css--color-to-4-dpc "#ffffff")
+                 (css--color-to-4-dpc "#fff")))
+  (should (equal (css--color-to-4-dpc "#aabbcc")
+                 (css--color-to-4-dpc "#abc")))
+  (should (equal (css--color-to-4-dpc "#fab")
+                 "#ffffaaaabbbb"))
+  (should (equal (css--color-to-4-dpc "#fafbfc")
+                 "#fafafbfbfcfc")))
+
+(ert-deftest css-test-named-color-to-hex ()
+  (dolist (item '(("black" "#000000")
+                  ("white" "#ffffff")
+                  ("salmon" "#fa8072")))
+    (with-temp-buffer
+      (css-mode)
+      (insert (nth 0 item))
+      (css--named-color-to-hex)
+      (should (equal (buffer-string) (nth 1 item))))))
+
+(ert-deftest css-test-format-rgba-alpha ()
+  (should (equal (css--format-rgba-alpha 0) "0"))
+  (should (equal (css--format-rgba-alpha 0.0) "0"))
+  (should (equal (css--format-rgba-alpha 0.00001) "0"))
+  (should (equal (css--format-rgba-alpha 1) "1"))
+  (should (equal (css--format-rgba-alpha 1.0) "1"))
+  (should (equal (css--format-rgba-alpha 1.00001) "1"))
+  (should (equal (css--format-rgba-alpha 0.10000) "0.1"))
+  (should (equal (css--format-rgba-alpha 0.100001) "0.1"))
+  (should (equal (css--format-rgba-alpha 0.2524334) "0.25")))
+
+(ert-deftest css-test-hex-to-rgb ()
+  (dolist (item '(("#000" "rgb(0, 0, 0)")
+                  ("#000000" "rgb(0, 0, 0)")
+                  ("#fff" "rgb(255, 255, 255)")
+                  ("#ffffff" "rgb(255, 255, 255)")
+                  ("#ffffff80" "rgba(255, 255, 255, 0.5)")
+                  ("#fff8" "rgba(255, 255, 255, 0.5)")))
+    (with-temp-buffer
+      (css-mode)
+      (insert (nth 0 item))
+      (css--hex-to-rgb)
+      (should (equal (buffer-string) (nth 1 item))))))
+
+(ert-deftest css-test-rgb-to-named-color-or-hex ()
+  (dolist (item '(("rgb(0, 0, 0)" "black")
+                  ("rgb(255, 255, 255)" "white")
+                  ("rgb(255, 255, 240)" "ivory")
+                  ("rgb(18, 52, 86)" "#123456")
+                  ("rgba(18, 52, 86, 0.5)" "#12345680")))
+    (with-temp-buffer
+      (css-mode)
+      (insert (nth 0 item))
+      (css--rgb-to-named-color-or-hex)
+      (should (equal (buffer-string) (nth 1 item))))))
+
+(ert-deftest css-test-cycle-color-format ()
+  (with-temp-buffer
+    (css-mode)
+    (insert "black")
+    (css-cycle-color-format)
+    (should (equal (buffer-string) "#000000"))
+    (css-cycle-color-format)
+    (should (equal (buffer-string) "rgb(0, 0, 0)"))
+    (css-cycle-color-format)
+    (should (equal (buffer-string) "black"))))
+
 (ert-deftest css-mdn-symbol-guessing ()
   (dolist (item '(("@med" "ia" "@media")
                   ("@keyframes " "{" "@keyframes")
@@ -301,6 +368,12 @@
   (should (equal (css--hex-color "#aabbcc") "#aabbcc"))
   (should (equal (css--hex-color "#aabbccdd") "#aabbcc")))
 
+(ert-deftest css-test-hex-alpha ()
+  (should (equal (css--hex-alpha "#abcd") "d"))
+  (should-not (css--hex-alpha "#abc"))
+  (should (equal (css--hex-alpha "#aabbccdd") "dd"))
+  (should-not (css--hex-alpha "#aabbcc")))
+
 (ert-deftest css-test-named-color ()
   (dolist (text '("@mixin black" "@include black"))
     (with-temp-buffer