[Development] resolution independence (was Re: Retina display support)

Samuel Rødal samuel.rodal at digia.com
Mon Oct 1 15:10:58 CEST 2012

On 10/01/2012 01:52 PM, Atlant Schmidt wrote:
> Folks:
>  > Likewise the idea that HiDPI displays are always "2x" seems to me another
>  > inelegant hack.  Actually the DPI varies between devices, so
> high-resolution
>  > art should not always need to be exactly 2x the normal size.  It may be
>  > convenient, but it's not the kind of "solution" we can expect to last
> very long.
>  > I wouldn't be surprised if Apple themselves changes their tune later.
>    At a minimum, we already have the situation where the iPhone4/4s/5, New
>    iPad, and Macbook Pro Retina Display all are “high pixel density”
> displays
>    but all three families have different pixel densities. For a display that
>    **MUST** conform to a certain physical limit (e.g., “all characters
> displayed
>    must be 5mm in height”, this would require being able to use the
>    information about the true and varying pixel density.
>                                                     Atlant

Specifying that all characters must be 5mm in physical height is 
typically not what a UI wants in any case, since different types of 
displays (mobiles / tablets, computer monitors, and TVs) are typically 
viewed at different distances. That's why logical DPI is such a useful 
concept, since it basically defines a scale factor that's independent 
from the physical DPI, and which can be controlled by the end user 
through window manager settings or other, depending on eye sight or 
simply based on preference.

Physical sizes _might_ be useful for touch UIs where you want a button 
or a slider to have a size that makes the control easy to hit with a finger.


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