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

Samuel Rødal samuel.rodal at digia.com
Wed Oct 3 12:12:39 CEST 2012

On 10/02/2012 01:58 PM, Atlant Schmidt wrote:
> 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

Sure, that assumes that the distance the application will be viewed at 
is constant though, and makes it hard to port to another display type 
unless you made the font size configurable in a different way. In some 
cases that is acceptable since the application is not meant to be portable.

Since logical DPI is how Windows and Linux at least (not sure about 
Mac?) let you control font scaling in a global way, I'd say that Qt's 
suggestion for scalable UIs should be to use point sizes and not 
physical size or pixels to specify the size of fonts. The logical DPI 
can then be set based on viewing distance, resolution, and user preference.


More information about the Development mailing list