Specifying sensible device types to use an application on in the desktop file

[Matthias Klumpp]

Am Fr., 9. Okt. 2020 um 16:46 Uhr schrieb Marco Martin <notmart at gmail.com>:
>
> On Fri, Oct 9, 2020 at 4:17 PM Matthias Klumpp <matthias at tenstral.net> wrote:
> > So within AppStream, apps will highly likely in addition to defining
> > their user input methods also be able to set preferred screen sizes
> > with an upper and lower limit.
>
> pixels or millimeters? (would prefer the second)

Haha, this was one of the arguments we had a year ago when this first
came up. Personally I would always prefer SI units, but for screen
sizes inches seem to be the way more common unit, for pixel-density
dpi[1] (dots per inch) is the common way to describe it in both
marketing material as well as technical documentation. So breaking
with that may be an issue. It was suggested to make this configurable,
e.g. via something like this: `<screen_size
unit="cm">14</screen_size>` - I do hate that though because it forces
AppStream using apps to do unit conversions and makes reading these
values harder.
But that is pretty much detail work, we can have a huge imperial vs
metric fight later :-)

The reason the screen sizes issue has been stalled for so long in
AppStream was that defining a "screen size" is harder than you would
think, and also that we didn't really know which values are actually
interesting to have in there. E.g. the screen resolution, screen size
and aspect ratio may all be interesting. Furthermore, some displays,
like for watches, may not be squares but round instead or have other
interesting shapes.

Personally, I think to solve this it makes a lot of sense to look at
the Android metadata[2] and quite possibly base the future AppStream
tags off of that. I've started writing a draft as an initial
suggestion for people to comment on, but it's not done yet (multiple
real-world events have kept me from completing it, annoyingly). In any
case, I really want this addressed for AppStream 1.0 - last time the
discussion faded away with a "it's complicated..." result, this time I
think Linux on mobile has advanced enough that we should be able to
tackle this properly and specify metadata that is actually useful for
software centers, application authors, and apparently app launchers as
well now :-)

Cheers,
    Matthias

[1]: https://en.wikipedia.org/wiki/Pixel_density
[2]: https://developer.android.com/guide/practices/screens-distribution

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