Rewrite the sprites CSS builder with XQuery

This makes the CSS file 3 times lighter (1.8KB→0.6KB)

Makefile

@@ -16,5 +16,5 @@ img/sprites.png: $(sprites)
 	chmod a+r $@
 
 css/sprites.css: img/sprites.png
-	find img/sprites -mindepth 1 -maxdepth 1 -type f -name '*.png' -printf '%f\n' | sort | awk '{ sub(/\.png$$/, ""); print ".icon-" $$0 " {\n\tdisplay: inline-block;\n\tposition: relative;\n\ttop: 4px;\n\tmargin-right: 2px;\n\tbackground-image: url(../img/sprites.png);\n\twidth: 16px;\n\theight: 16px;\n\tbackground-position: " (-(NR-1)*16) "px;\n}" }' > $@
+	xidel --silent --extract-kind=xquery3 --extract-file=xquery/build_sprites_css.xqy > $@
 	chmod a+r $@

xquery/build_sprites_css.xqy

@@ -0,0 +1,19 @@
+xquery version "3.0" encoding "utf-8";
+
+let $sprites :=
+  for $file in file:children(file:resolve-path("./img/sprites/"))
+  where ends-with($file, ".png")
+  order by $file
+  return concat(".icon-", substring-before(file:name($file), ".png"))
+
+return concat(
+  (: Styles that apply to all icons at once :)
+  string-join($sprites, ", "),
+  " { display: inline-block; position: relative; top: 4px; margin-right: 2px; background-image: url(../img/sprites.png); width: 16px; height: 16px; }",
+  (: Add an offset for the position of each sprite within the image :)
+  string-join(
+    for $sprite in $sprites
+    count $i
+    return concat($sprite, " { background-position: ", -($i - 1)*16, "px; }")
+  )
+)