converted all flag enums into constexpr uints

[mkalte666]

follow up on #2993 (comment)

[rokups]

This change prevents compiler from ensuring that we do not mix incompatible flags at build time. A more proper solution would be to define bitwise operators for enums in question to enable using them as flags.

[mkalte666]

I did not consider that but you are right. Oops.

[ocornut]

We don’t guarantee that currently and I am not sure it is worth pursuing this because: - 0 is a convenient default to use we want to allow that. - we want private/internal flags not declared in imgui.h. As with most of c++ design, encapsulation and privacy are designed all wrong and it gets even trickier if you want to allow that with custom ops. - I don’t know how to implement those strongly typed operators without unnecessary debug-build overhead. So to me the PR doesn’t introduce any regression and is perfectly valid as is.

[mkalte666]

Is there a way to introduce type safety for flags while still allowing for this convenience without significant overhead?

I cannot think of anything.