hide year headings when all items are hidden

fixes #7

make-pages/GalleryPage.hs

@@ -122,7 +122,7 @@ makeYearItems :: Bool -- ^ nsfw
               -> [(FilePath, Info)]
               -> Builder
 makeYearItems nsfw year infos = [b|@4
-    <li class="item year-marker">
+    <li class="item year-marker" id="marker-$year">
       <span class=year-text>$year'</span>
     $4.items
   |]
@@ -132,7 +132,8 @@ makeYearItems nsfw year infos = [b|@4
 
 makeItem :: Bool -> FilePath -> Info -> Builder
 makeItem nsfw file info@(Info {title, bg}) = [b|@4
-    <li class="item post$nsfw'" data-date="$date'" data-updated="$updated'"
+    <li class="item post$nsfw'" data-date="$date'" data-year=$year'
+        data-updated="$updated'"
         data-tags="$tags'">
       <figure>
         <a href="$dir">
@@ -149,6 +150,8 @@ makeItem nsfw file info@(Info {title, bg}) = [b|@4
   thumb    = getThumb dir info
   nsfw'    = if nsfw && #anyNsfw info then [b| nsfw|] else ""
   tags'    = fold $ intersperse ";" $ map fromText $ tagsFor nsfw info
-  date'    = formatShort $ #latestDate info
+  date     = #latestDate info
+  date'    = formatShort date
+  year'    = #year date
   updated' = if #updated info then [b|true|] else [b|false|]
   bgStyle  = ifJust bg \col -> [b| style="background: $col"|]