Put stripes() definition behind a <1d-image> type to make it easily extensible

Author: SebastianZ

css-backgrounds-4/Overview.bs

@@ -185,24 +185,24 @@ Painting Area: the 'background-clip' property</h3>
 
 	<pre class=propdef>
 	Name: border-top-color, border-right-color, border-bottom-color, border-left-color
-	Value: <<color>> || <<stripes()>>
+	Value: <<color>> || <<1d-image>>
 	Initial: currentcolor
 	Applies to: all elements
 	Inherited: no
 	Percentages: n/a
-	Computed Value: the computed color and/or <<stripes()>> function
+	Computed Value: the computed color and/or a one-dimensional image function
 	Animation type: see prose
 	</pre>
 
 	<pre class="propdef shorthand">
 	Name: border-color
-	Value: [ <<color>> || <<stripes()>> ]{1,4}
+	Value: [ <<color>> || <<1d-image>> ]{1,4}
 	</pre>
 
 	These properties set the foreground color of the border specified
 	by the 'border-style' properties.
 
-	The stripes defined by the <<stripes()>> function follow the direction of
+	The stripes defined by <<1d-image>> follow the direction of
 	the side the border is applied on (i.e. horizontally on left and
 	right borders and vertically on top and bottom borders), starting outwards.
 	With that, the corresponding 'border-*-width' property defines the total
@@ -711,7 +711,7 @@ Additions Since Level 3</h3>
 		<li>logical 'background-position' values (''background-position/start'', ''background-position/end'')
 		<li>the ''extend'' keyword of 'background-repeat'
 		<li>'corner-shape'
-		<li><<stripes()>> as value for ''border-color'' and its longhands
+		<li><<1d-image>> as value for ''border-color'' and its longhands
 		<li>multiple border colors per border
 		<li>logical border properties
 		<li><a href="#partial-borders">Partial Borders</a> (make part of border shorthand as well!)

css-images-4/Overview.bs

@@ -72,7 +72,7 @@ Value Definitions {#values}
 	or <a section href="#gradients">gradient notation</a>.
 	Its syntax is:
 
-	<pre class="prod"><dfn>&lt;image></dfn> = <<url>> | <<image()>> | <<image-set()>> | <<cross-fade()>> | <<element()>> | <<gradient>> | <<stripes()>></pre>
+	<pre class="prod"><dfn>&lt;image></dfn> = <<url>> | <<image()>> | <<image-set()>> | <<cross-fade()>> | <<element()>> | <<gradient>> | <<1d-image>></pre>
 
 	An <<image>> can be used in many CSS properties,
 	including the 'background-image', 'list-style-image', 'cursor' properties [[!CSS2]]
@@ -1910,9 +1910,10 @@ Color Stop “Fixup”</h4>
 	The ''stripes()'' function allows to define a number of stripes of
 	different colors with different widths.
 
-	The syntax for ''stripes()'' is defined as:
+	The syntax for ''1d-image'' and ''stripes()'' is defined as:
 
 	<pre class=prod>
+		<dfn>&lt;1d-image></dfn> = <<stripes()>>
 		<dfn>stripes()</dfn> = stripes( [ <<color>> && [ <<length-percentage>> | <<flex>>]? ]# )
 	</pre>
 
@@ -2501,7 +2502,7 @@ Changes {#changes}
 - Switched color-stop grammar to repeat at end for readability
 - Clarified that object-fit and image-resolution use discrete animation
 - Fixed definition of cross-fade() image blending
-- Added stripes() function and added it to &lt;image> data type
+- Added &lt;1d-image> data type and stripes() function and added &1d-image> to &lt;image> data type
 - Moved interpolation of images from [[css3-images]]
 - Clarifed that cross-fade() takes 1+ arguments. Defined sizing and painting of the new function arguments in detail.
 - Moved cross-fade() from [[css3-images]]

css-ui-4/Overview.bs

@@ -287,14 +287,14 @@ Animation type: by computed value
 
 <pre class="propdef">
 Name: outline-color
-Value: [ <<color>> || <<stripes()>> ] | invert
+Value: [ <<color>> || <<1d-image>> ] | invert
 Initial: invert
 Applies to: all elements
 Inherited: no
 Percentages: N/A
 Computed value: The computed value for ''outline-color/invert'' is ''outline-color/invert''.
  For <<color>> values, see [[!CSS-COLOR-4#resolving-color-values]] in [[!CSS-COLOR-4]].
- <<stripes()>> values are computed as defined in their definition.
+ <<1d-image>> values are computed as defined in their definition.
 Animation type: by computed value
 </pre>
 
@@ -2550,7 +2550,7 @@ the following normative changes have been made:
 		(Support for the broader <<image>> type remains allowed but optional.)
 
 	<li>
-		Added <<stripes()>> as value for the 'outline-color' property.
+		Added <<1d-image>> as value for the 'outline-color' property.
 </ul>
 
 <h3 id=changes-24-1-2020 class=no-num>Changes from the