Re: Confusion about screen resolution
Re: Confusion about screen resolution
- Subject: Re: Confusion about screen resolution
- From: Quincey Morris via Cocoa-dev <email@hidden>
- Date: Sat, 22 Feb 2020 18:34:21 -0800
On Feb 22, 2020, at 15:31 , Gabriel Zachmann via Cocoa-dev
<email@hidden> wrote:
>
> I was always under the impression that the backing store is 2x the size of
> the display.
> That should be then 2x( 2880 x 1800 ), i.e., 5760 x 3600 , shouldn't it?
>
> So, either the frameRect should be 2880x1800 or 5760 x 3600 , both would
> make sense to me.
As multiple people have said, this isn’t true any more.
If you go to the Displays pane of System Preferences, and choose the Scaled
option, you will see (at least, I see on a 27” iMac) 5 different size settings.
Each one of the represents a different screen size *in points*. The smaller the
dimensions in points, the larger a point is, since the point size is
“stretched” to fit the physical display.
The way things are now, starting from the selected Displays pane point size,
whatever that happens to be, the backing store is 2x or 3x — an integral scale
*up* — and the result is scaled — typically *down* by a non-integral amount —
to the hardware physical pixel dimensions of the screen.
None of this should matter to your code.
> I am just curious, how do they do that given the fact that they first render
> it into a backing store and then scale it down by some very odd factor, which
> is definitely not 2 or 1 or some other similar "easy" case. How is that I am
> not seeing any resampling artefacts.
It works because of the implicit scaling up to an abnormally high resolution in
the backing store. The introduces enough detail so that the fractional
scale-down factor looks great in most cases. (However, if you try some of the
extreme scaled Display resolutions, you’ll probably think they look a bit soft
or fuzzy.)
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