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

[Atlant Schmidt]

Samuel:

> 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.

  In my world (medical devices), it's entirely *TYPICAL*
  that there will be specifications on the size of the
  text. Realistically, it may be a spec on the minimum
  size of the text (so that it is readable by the elderly)
  but we can't go bigger either because the text won't
  fit.

  And yes, our interface is a touch screen so buttons
  must also be specified in real physical sizes.

  In other words, we need a solution that lets us specify
  the actual rendered size of the text on the screen.

                                     Atlant

-----Original Message-----
From: development-bounces+aschmidt=dekaresearch.com at qt-project.org [mailto:development-bounces+aschmidt=dekaresearch.com at qt-project.org] On Behalf Of Samuel Rødal
Sent: Monday, October 01, 2012 9:11 AM
To: development at qt-project.org
Subject: Re: [Development] resolution independence (was Re: Retina display support)

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.

--
Samuel


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