> On Feb 19, 2020, at 5:29 AM, Martin Koppenhoefer <dieterdre...@gmail.com>
> wrote:
>
> I am not sure what "device-independent pixels" means. Is this about points
> (i.e. physical, hardware screen pixels divided by the scale)? IMHO we should
> require actual, physical pixels, because it is them who determine whether the
> attribution string will be readable --- and the requirement should be
> tougher. We have seen many examples of easily readable, unobtrusive
> attribution on much smaller maps. For example the osm.org <http://osm.org/>
> website on 467 pixels wide has room for a scale bar and this text: "©
> OpenStreetMap contributors # Make a Donation. Website and API terms" in a
> single line.
>
> The actual requirement for "© OpenStreetMap contributors" is around 163
> pixels. My suggestion would be to make this half: 250 pixels, maybe even less
> like 200 (theoretical) pixels for retina screens (i.e. 400 actual pixels on
> retina@2x and 600 actual pixels on retina@3x).
> Our goal is not to avoid attribution but to show it when it can reasonably be
> done.
Device-independent pixels are a concept used in CSS in response to the
high-resolution screens available for the past few years. Since actual,
physical pixels are now very small, a new definition expresses them in terms of
visual angle so that pixel-defined CSS layouts from the past few decades aren’t
suddenly illegible: “By definition, this is the physical size of a single pixel
at a pixel density of 96 DPI, located an arm's length away from the viewer's
eyes.”
https://developer.mozilla.org/en-US/docs/Glossary/CSS_pixel
For our purposes, this is a better definition because it’s defined in terms of
what a viewer can see rather than its implementation in hardware.
-mike.
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