We need to account for the scale factor under GTK+ (and, presumably,
under macOS) to compute the correct PPI value as it must use the number
of physical and not logical pixels.
While this is not done for all the ports yet, the new API allows
returning different PPI values for different monitors, unlike the old
(and still existing, but implemented in terms of the new one) global
function.
Allow getting the depth of any display, not just the primary one, even
though this is not implemented for Unix ports currently.
Mostly do this for consistency with the other display-related functions.
Simplify the code by not making this function pure virtual as all the
ports except MSW had to override it just to return an empty string.
Instead, just return empty string by default as it's not critical to
force the derived classes to override this function.
Instead of forwarding to these functions from wxDisplay implementation
in wxUSE_DISPLAY==0 case, make the functions themselves wrappers around
wxDisplay, which may, or not, depending on the platform, have a simpler
implementation in wxUSE_DISPLAY==0 case, but is always available in any
case.
As part of this change, only use src/osx/core/display.cpp in macOS
builds, not iOS ones and update the Xcode project accordingly too.
This cuts down on code duplication, especially in wxGTK, and facilitates
further additions to wxDisplay API.
Avoid a heap allocation on every wxDisplay creation by caching the
wxDisplayImpl objects once they're created.
Currently we never invalidate the cache, but we should add a way to do
it in the future.
This speeds up wxDisplay::GetGeometry() benchmark by a factor of 4.
