title: iOS MTKView (Metal Kit view) draws image without proper scale
body: <p>I don't understand why MTKView doesn't use device's scale.</p>
  
  <p>I have a retina device: 2x scale, MTKView.bounds of 400x200, and CIImage size of 800x400, but it draws only left bottom quarter of the image.</p>
  
  <p>Strangely drawableSize returns bounds size (400x200).</p>
  
  <p>Here's the code I use:</p>
  
  <pre><code>id&lt;MTLTexture&gt; targetTexture = self.currentDrawable.texture;
  id&lt;MTLCommandBuffer&gt; commandBuffer = [commandQueue commandBuffer];
  
  [ctx render:coreImage toMTLTexture:targetTexture commandBuffer:commandBuffer bounds:self.bounds colorSpace:colorSpace];
  
  [commandBuffer presentDrawable:self.currentDrawable];
  [commandBuffer commit];
  </code></pre>