Add IDpiAwareGLContext.

Dashboard.Drawing.OpenGL/IGLContext.cs

@@ -23,4 +23,20 @@ namespace Dashboard.Drawing.OpenGL
         /// </summary>
         event Action Disposed;
     }
+
+    /// <summary>
+    /// Extension interface for GL contexts in a DPI-aware environment.
+    /// </summary>
+    public interface IDpiAwareGLContext : IGLContext
+    {
+        /// <summary>
+        /// Dpi for current context.
+        /// </summary>
+        public float Dpi { get; }
+
+        /// <summary>
+        /// Scale for the current context. This will be used to scale drawn geometry.
+        /// </summary>
+        public float Scale { get; }
+    }
 }