Toggling viewports on and off can cause visual anomalies such as flicker when moving windows between displays on a mixed-DPI configuration or toggling the scaled fullscreen modes. If the viewport protocol is avilable, always create a viewport for the surface, unless it is an unscaled external surface, in which case the surface should be left untouched as an application may wish to attach its own viewport or use integer scaling.
This allows for the removal of several helper functions as well.
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