Update BeatmapInfoWedge design

- Adds colour difficulty strip.
- Adjusts paddings.
- Fixes source/artist confusion.
- Double dash to em-dash.

osu.Game/Beatmaps/Drawables/DifficultyColouredContainer.cs

@@ -0,0 +1,69 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Allocation;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Database;
+using osu.Game.Graphics;
+using OpenTK.Graphics;
+
+namespace osu.Game.Beatmaps.Drawables
+{
+    internal class DifficultyColouredContainer : Container, IHasAccentColour
+    {
+        public Color4 AccentColour { get; set; }
+
+        private readonly BeatmapInfo beatmap;
+        private OsuColour palette;
+
+        public DifficultyColouredContainer(BeatmapInfo beatmap)
+        {
+            this.beatmap = beatmap;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuColour palette)
+        {
+            this.palette = palette;
+            AccentColour = getColour(beatmap);
+        }
+
+        private enum DifficultyRating
+        {
+            Easy,
+            Normal,
+            Hard,
+            Insane,
+            Expert
+        }
+
+        private DifficultyRating getDifficultyRating(BeatmapInfo beatmap)
+        {
+            var rating = beatmap.StarDifficulty;
+
+            if (rating < 1.5) return DifficultyRating.Easy;
+            if (rating < 2.25) return DifficultyRating.Normal;
+            if (rating < 3.75) return DifficultyRating.Hard;
+            if (rating < 5.25) return DifficultyRating.Insane;
+            return DifficultyRating.Expert;
+        }
+
+        private Color4 getColour(BeatmapInfo beatmap)
+        {
+            switch (getDifficultyRating(beatmap))
+            {
+                case DifficultyRating.Easy:
+                    return palette.Green;
+                default:
+                case DifficultyRating.Normal:
+                    return palette.Yellow;
+                case DifficultyRating.Hard:
+                    return palette.Pink;
+                case DifficultyRating.Insane:
+                    return palette.Purple;
+                case DifficultyRating.Expert:
+                    return palette.Gray0;
+            }
+        }
+    }
+}