CSS: Justify use of rtrim on CSS property values

CSS does not acknowledge carriage return or form feed characters
as whitespace but it does replace them with whitespace, making it
acceptable to use `rtrim`.

Closes gh-4956

diff --git a/src/css/curCSS.js b/src/css/curCSS.js
index 6d8b6a2d3bd25e8dde11a41c40ffbe3a69ea7d9d..15d624bbb98cfc506a57da5c4db0b8cf17841cbc 100644 (file)
--- a/src/css/curCSS.js
+++ b/src/css/curCSS.js
@@ -16,6 +16,12 @@ function curCSS( elem, name, computed ) {
 
                // trim whitespace for custom property (issue gh-4926)
                if ( isCustomProp ) {
+
+                       // rtrim treats U+000D CARRIAGE RETURN and U+000C FORM FEED
+                       // as whitespace while CSS does not, but this is not a problem
+                       // because CSS preprocessing replaces them with U+000A LINE FEED
+                       // (which *is* CSS whitespace)
+                       // https://www.w3.org/TR/css-syntax-3/#input-preprocessing
                        ret = ret.replace( rtrim, "$1" );
                }