With HiDPI support it's no longer just about window size changing -- if
the framebuffer size is different than window size, on resize both are
changed to new (different) values. Other than that, for example, when
moving a window from one display to another with a different DPI,
all three of window size, framebuffer size and DPI scaling can change as
well. This should be all reflected in the event.
This change is done in all Application classes, but the full
implementation is only in the SDL2 implementation at the moment, as the
others don't have full HiDPI support implemented yet. The old
viewportEvent(const Vector2i&) is deprecated and for backwards
compatibility called with either framebufferSize() or windowSize()
(depending on level of HiDPI support) from the new event. Overriding the
old one will still work as expected (in case you build with
MAGNUM_BUILD_DEPRECATED enabled and use the `override` keyword -- which
you should); overriding the new one will cause the compat implementation
to not be called anymore.
In order to make it possible to preserve backwards compatibility, the
viewportEvent() is no longer pure virtual in Screen. That's also
consistent with all Application implementations.
Vladimír Vondruš