DateChooser: even better date/time widgets

[cyrilRomain]

Major rewrite except the calendar display algorithm.

New API:

• InputDate: date chooser
• InputTime: time chooser
• InputDateTime: date and time chooser

Features improvments:

• display sundays on right
• add a today goto button 'o' (similar to thunderbird)
• highlight today, selected and hovered days (w/ different colors)

Code:

• removed datechooser original implementation
• removed SetDate* functions, it is up to the user to setup struc tm
• kept the calendar display algorithm
• support more strict compilation

Examples:

• imguidatechooser to imgui_datetime

[Flix01]

@cyrilRomain, thank you for your effort!

I still have to test it, but I think that having three widgets is better than one!

Some notes:

• Maybe renaming it to imguidatetimechooser.h/.cpp is more consistent with other addons (and also adding "Chooser" to the function names) [*].
• Displaying sundays on right might not be what people want (in many cultures, and from an historical point of view, sunday is the first day of the week [see the wiki about it]).
• A screenshot of the new widgets could be handy to see the result.

But, aside from these things, I think it's a useful improvement. Thank you again for having spent your time on it.

Edit: [*] Maybe imguiinputdatetime.h/.cpp or just imguidatetime.h/.cpp could be OK. and having the "Input" prefix is more consistent with other Imgui widgets... so it was a good choice not to append "Chooser" when "Input" is used. In short: forget point 1: just removing the underscore in imgui_datetime is OK for me.

[cyrilRomain]

@Flix01 thank for your feedback

• added a commit to address consistency point
• regarding sundays I followed ISO 8601. I added a commit though to enable sunday first, but w/o customization i.e. user has to change the hardcoded sunday_first variable.
• DateTime screenshot (available for download for 1 month)

@Flix01's edit: (pasted the screenshot here):

[Flix01]

Seems OK to me. Just one more thing before merging it:

Can you please modify the code this way?

#ifdef IMGUIDATETIME_DISPLAYSUNDAYFIRST
static bool sunday_first = true; // display sundays first (like before)
#else
static bool sunday_first = false; // display mondays first as ISO 8601 suggest
#endif

[cyrilRomain]

Good point. Fix done in last commit (with file renaming I forgot to rename back w/o "chooser"). Feel free to squash when merging.