'Visible screen area' refers to the area where pictures and videos are displayed, so the area with pixels. A framework of glass, plastic or metal outside the pixel area does not count as visible screen area.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.