Initializing GraphicsWindow layout & children requires cooperation from
the graphics stack: on my system, for example, it causes a Vulkan
context to get created in order to get driver info. This is a slow
operation, and right now it is taking about 60-70% of the Dolphin
startup time on my system.
Move instead to a lazy-initialization model where the constructor
does nothing, instead offloading work to a separate Initialize() method
called before the window is shown.
I would expect this should be done for other larger parts of the UI,
especially the ones where creating widgets ends up triggering large IO
subsystems (I suspect controller configuration might be doing that).
(I'm not super happy with how this is implemented, but right now it's a
one-off, and it's a major complaint users have with the new UI. I
prioritized getting something working quickly...)
Without this macro, if any signals or slots were attempted to be used,
they wouldn't work; neither would various other features of the Qt
meta-object system. This can also lead to weird behavior in other
circumstances. Qt's documentation specifically states:
"Therefore, we strongly recommend that all subclasses of QObject use the
Q_OBJECT macro regardless of whether or not they actually use signals,
slots, and properties."
on its page for "The Meta-Object System", which can be seen here:
https://doc.qt.io/qt-5/metaobjects.html
Let's opt for "always do the right thing", and keep the code extensible
for the future and not have random things blow up on us.
This makes it possible to use enums as the config type.
Default values are now clearer and there's no need for casts
when calling Config::Get/Set anymore.
In order to add support for enums, the common code was updated to
handle enums by using the underlying type when loading/saving settings.
A copy constructor is also provided for conversions from
`ConfigInfo<Enum>` to `ConfigInfo<underlying_type<Enum>>`
so that enum settings can still easily work with code that doesn't care
about the actual enum values (like Graphics{Choice,Radio} in DolphinQt2
which only treat the setting as an integer).
Pierre Bourdon