Pixels Per Inch needs to be standardized 🔍

Pekka Paalanen ppaalanen at gmail.com
Thu May 5 10:28:32 UTC 2016

On Thu, 5 May 2016 03:24:29 +0200
Alberto Salvia Novella <es20490446e at gmail.com> wrote:

> Pekka Paalanen:
> > too bad the discussion does not explain why you need the ppi, or
> > what it would be used for.  
> What I am asking for is a standard way to advertise the desktop scale 
> factor. And it does not necessarily need to be about pixel density, it 
> just could be a multiplier like x1.5 or x2.
> Pekka Paalanen:
>  > Or, how would a DE know which ppi it needs to advertise at a time?  
> One scale factor per screen.

Oh scale factor! Yes, that is a completely different thing. Please
do talk about a scale factor instead of dpi or ppi. People will
respond much better, while dpi tends to raise hard prejudice (with
me too) due to its history of abuse and misconceptions.

So this is about HiDPI? That would be a good term to use too, as
HiDPI support also uses a scale factor, not dpi.

FWIW, Wayland offers it like this: each wl_output (usually
represents a single monitor) has an integer scale factor
associated. The client/app/toolkit gets told on which outputs a
window is shown on, and then the app can choose what size and
factor to draw in. The compositor automatically accounts for the
mismatch between the draw factor and output factor. (wl_outputs
also advertise resolution and physical size, if applicable, so it
is also possible to compute ppi.) This is built in the core of the
Wayland display protocol.

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