Which video depths are actually used by macOS?

[Michael Crawford]

The IOFramebuffer driver - a component of the IOGraphicsFamily -
supports 8, 16 and 32 bit.

However there is no UI for setting the bit depth in the Display Prefs.
That leads me to believe that only 32 bit is ever used.

Is that the case?

I Am Eternally In Your Debt,

Mike Crawford
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[Phil Dennis-Jordan]

Hi Mike,

On Fri, Dec 8, 2017 at 9:21 PM, Michael Crawford <mi...@soggywizards.com> wrote:
> The IOFramebuffer driver - a component of the IOGraphicsFamily -
> supports 8, 16 and 32 bit.
>
> However there is no UI for setting the bit depth in the Display Prefs.
> That leads me to believe that only 32 bit is ever used.
>
> Is that the case?

If given it that choice, I have indeed never seen WindowServer pick
anything other than 32-bit mode since Mac OS X 10.6 or so. There's
little point in offering other depths, it just adds unnecessary
complexity to your code. Some iMacs use a higher bit depth than that;
the headers also declare some YUV pixel formats. I've not experimented
with unaccelerated IOFramebuffers that support any of these, but I
suspect you'll be safest if you do any conversions you might need
after grabbing the 32-bit RGB image.

Hope that helps,

Phil