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So in affect, the application drew a GUIDE in 1280x720 and it appeared perfectly scaled on a 3840x2160 TV. 

There are a couple assumptions made at this point:

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• MUST support Video-graphics display compositing layering functions
• Compositing of Graphics on Video using
  • an opaque graphics overlay,
  • a translucent (alpha blended) overlay, or
  • picture in graphics
• RGB and YUV color spaces
  • color space conversion between these
• MUST scale graphics to the current output resolution of the display

Z-Ordering

The graphics and video planes need to be arranged to form a cohesive display framework. 

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RDK Graphics Stack Architecture

RDK uses Qt/WPE Webkit as the windowing framework and OpenGL/ES as the graphics engine, application rendering and user input framework. Creating an OpenGL context is quite a complex process & it varies between Operating Systems. Automatic OpenGL context creation has become a common feature of several user-interface libraries, including Qt and WPE.

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