Makes the "toggle video" button in the call window active only if we're ready...

Makes the "toggle video" button in the call window active only if we're ready to send video, and shows an appropriate tooltip otherwise. Same for the desktop sharing button.

src/org/jitsi/service/neomedia/codec/EncodingConfiguration.java

@@ -501,4 +501,17 @@ public void loadEncodingConfiguration(
         encodingConfiguration.storeProperties(properties);
         loadProperties(properties);
     }
+
+    /**
+     * Returns <tt>true</tt> if there is at least one enabled format for media
+     * type <tt>type</tt>.
+     *
+     * @param mediaType The media type, MediaType.AUDIO or MediaType.VIDEO
+     * @return <tt>true</tt> if there is at least one enabled format for media
+     * type <tt>type</tt>.
+     */
+    public boolean hasEnabledFormat(MediaType mediaType)
+    {
+        return (getEnabledEncodings(mediaType).length > 0);
+    }
 }