feature: Android renderers

Pixiview.Android/Renderers/RoundLabelRenderer.cs

@@ -0,0 +1,70 @@
+using Android.Content;
+using Android.Graphics;
+using Android.Graphics.Drawables;
+using Pixiview.Droid.Renderers;
+using Pixiview.UI;
+using Xamarin.Forms;
+using Xamarin.Forms.Platform.Android;
+
+[assembly: ExportRenderer(typeof(RoundLabel), typeof(RoundLabelRenderer))]
+namespace Pixiview.Droid.Renderers
+{
+    public class RoundLabelRenderer : Xamarin.Forms.Platform.Android.FastRenderers.LabelRenderer
+    {
+        public RoundLabelRenderer(Context context) : base(context)
+        {
+        }
+
+        protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
+        {
+            base.OnElementChanged(e);
+
+            if (e.NewElement is RoundLabel label)
+            {
+                var density = Resources.DisplayMetrics.Density;
+                var drawable = new RoundCornerDrawable(label.CornerRadius * density);
+                drawable.SetColorFilter(label.BackgroundColor.ToAndroid(), PorterDuff.Mode.Src);
+                Control.SetBackground(drawable);
+            }
+        }
+    }
+
+    public class RoundCornerDrawable : Drawable
+    {
+        private readonly Paint paint;
+        private readonly float radius;
+        private RectF rect;
+
+        public override int Opacity => (int)Format.Translucent;
+
+        public RoundCornerDrawable(float radius)
+        {
+            paint = new Paint
+            {
+                AntiAlias = true
+            };
+            this.radius = radius;
+        }
+
+        public override void SetBounds(int left, int top, int right, int bottom)
+        {
+            base.SetBounds(left, top, right, bottom);
+            rect = new RectF(left, top, right, bottom);
+        }
+
+        public override void Draw(Canvas canvas)
+        {
+            canvas.DrawRoundRect(rect, radius, radius, paint);
+        }
+
+        public override void SetAlpha(int alpha)
+        {
+            paint.Alpha = alpha;
+        }
+
+        public override void SetColorFilter(ColorFilter colorFilter)
+        {
+            paint.SetColorFilter(colorFilter);
+        }
+    }
+}