Add black background, and a bg option

[asajeffrey]

Allows a black background.

[asajeffrey]

Rebased.

[pcwalton]

I was giving this some thought, and I was thinking what might work best is to change the "sun/moon" option slider into a popup that brings up a menu with "Light", "Dark", and "Transparent" options. Transparent would be what AR uses. This would also give us a transparent window on desktop, which could be a cool demo in its own right. What do you think?

[asajeffrey]

Fine by me.

[pcwalton]

This looks good once conflicts are resolved.

[asajeffrey]

A couple of thoughts...

If we have a transparent background, what should the native demo display? Black?

How about we put off the replacement of the buttons with a menu for a different PR?

[pcwalton]

If we have a transparent background, what should the native demo display? Black?

Well, ideally it would ask SDL to recreate the window in transparent mode. (We don't want to have SDL always create a transparent window because that will slow all rendering down in the opaque case by 4ms or more.)

That may be a bit of work, though. Black is OK for now (though honestly we shouldn't even display the "transparent" option in that case).

How about we put off the replacement of the buttons with a menu for a different PR?

That's OK.

[asajeffrey]

@pcwalton Care to press the big green merge button?

[asajeffrey]

Rebased.

[asajeffrey]

Rebased.

[pcwalton]

Commit c5ccd0f implements this.