Implement responsive generated covers with SVG

src/cljs/airsonic_ui/views/cover.cljs

@@ -1,7 +1,6 @@
 (ns airsonic-ui.views.cover
   (:require [re-frame.core :refer [subscribe]]
             [airsonic-ui.subs :as subs]
-            [airsonic-ui.components.highres-canvas.views :refer [canvas]]
             ["@hugojosefson/color-hash" :as ColorHash]))
 
 (def color-hash (ColorHash.))
@@ -10,36 +9,28 @@
   (str "hsl(" h "," (* 100 s) "%," (* 100 l) "%)"))
 
 (defn palette
-  "Generate a hsl palette of two colors that's unique for a given item"
-  [item]
-  (let [identifier (str (:artistId item) "-" (or (:albumId item) (:id item)))
-        [h s l] (js->clj (.hsl color-hash identifier))]
+  "Generate a unique hsl palette of two colors"
+  [identifier]
+  (let [[h s l] (js->clj (.hsl color-hash identifier))]
     [(hsl->css h s l)
      (hsl->css (mod (+ h (* h 0.3) 10) 360) s l)]))
 
-(defn generate-cover [ctx item]
-  (let [[a b] (palette item)
-        size (.. ctx -canvas -offsetWidth)
-        pad (* 0.02 size)
-        gradient (doto (.createLinearGradient ctx pad 0 (- size pad) size)
-                   (.addColorStop 0 a)
-                   (.addColorStop 1 b))]
-    (set! (.. ctx -canvas -height) (.. ctx -canvas -width))
-    (set! (.. ctx -canvas -style -height) (.. ctx -canvas -style -width))
-    ;; we have to re-scale everything because resizing messes with the content
-    (.scale ctx (.-devicePixelRatio js/window) (.-devicePixelRatio js/window))
-    (set! (.-fillStyle ctx) gradient)
-    (.fillRect ctx 0 0 (.. ctx -canvas -width) (.. ctx -canvas -height))))
-
 (defn missing-cover
   [item size]
-  [canvas {:class "missing-cover"
-           :draw #(generate-cover % item)}])
+  (let [identifier (str (:artistId item) "-" (or (:albumId item) (:id item)))
+        [color-a color-b] (palette identifier)]
+    [:svg.missing-cover {:viewBox "0 0 256 256"
+                         :xmlns "http://www.w3.org/2000/svg"}
+     [:defs [:linearGradient {:id (str "cover-gradient-" identifier)
+                              :x1 0, :y1 0,
+                              :x2 1, :y2 1}
+             [:stop {:offset "2%", :stop-color color-a}]
+             [:stop {:offset "98%", :stop-color color-b}]]]
+     [:rect {:x 0, :y 0, :width 256, :height 256
+             :fill (str "url(#cover-gradient-" identifier ")")}]]))
 
 (defn has-cover? [item]
-  (:coverArt item))
-
-;; FIXME: The direct dependency on these subs is a bit ugly
+  (some? (:coverArt item)))
 
 (defn cover
   [item size]

src/sass/app.sass

@@ -164,15 +164,15 @@
 
   &.is-48x48 .missing-cover
     width: 48px
-    height: 48px
+    height: auto
 
   &.is-128x128 .missing-cover
     width: 128px
-    height: 128px
+    height: auto
 
   &.is-256x256 .missing-cover
     width: 256px
-    height: 256px
+    height: auto
 
 // occurs in album detail view
 .table