[frio] Vary Back to Top element depending on the theme accent/colors

- Add specific support for dark/black schemes

view/theme/frio/css/style.css

@@ -119,7 +119,7 @@ blockquote {
 #back-to-top {
     display: none;
     cursor: pointer;
-    color: white;
+    color: $nav_icon_color;
     position: fixed;
     z-index: 49;
     right: 20px;
@@ -128,7 +128,7 @@ blockquote {
     font-size: 2.9em;
     padding: 0 12px 0 12px;
     border-radius: 10px;
-    background-color: #aaa;
+    background-color: $nav_bg;
     line-height: 1.5;
 }
 

view/theme/frio/php/default.php

@@ -149,7 +149,7 @@ $is_singleuser_class = $is_singleuser ? "is-singleuser" : "is-not-singleuser";
 				</div><!--row-->
 			</div><!-- container -->
 
-			<div id="back-to-top" title="back to top">&#8679;</div>
+			<div id="back-to-top" title="back to top">⇪</div>
 		</main>
 
 		<footer>

view/theme/frio/php/standard.php

@@ -70,7 +70,7 @@
 			</div><!--row-->
 		</div><!-- container -->
 
-		<div id="back-to-top" title="back to top">&#8679;</div>
+		<div id="back-to-top" title="back to top">⇪</div>
 	</main>
 
 <footer>

view/theme/frio/scheme/black.css

@@ -347,7 +347,9 @@ section > .generic-page-wrapper,
 .fsuggest-content-wrapper,
 .panel,
 aside .widget,
-.nav-container .widget{
+.nav-container .widget,
+#back-to-top
+{
 	box-shadow: 0 0 3px $link_color;
 	-webkit-box-shadow: 0 0 3px $link_color;
 }
@@ -355,3 +357,7 @@ aside .widget,
 input[type=text].tt-input {
 	box-shadow: none;
 }
+
+#back-to-top {
+	color: $link_color;
+}

view/theme/frio/scheme/dark.css

@@ -327,3 +327,7 @@ legend {
 input[type=text].tt-input {
 	box-shadow: none;
 }
+
+#back-to-top {
+	border: 1px solid $nav_icon_color;
+}