[Interest] High DPI support in QT (Windows)

Prav pr12og2 at programist.ru
Fri Sep 25 01:17:59 CEST 2015

> Behind the scenes the new 5.6 support is actually a rewrite, where
> we have moved the implementation from the platform plugins to QtGui.
I   wonder why this is such a big problem with high DPI people started
talking about recently? People already suffered  from  element's size
which are not suitable for them ... imagine human with bad eyes ...
he needs larger elements ... even on low DPI's

Sooo  ... it is not a problem of DPI ... the problem is that we design
in  pixels  for  humans  with  visibility abilities as for designer or
programer ... this is the problem.

Why  not to solve it once and forever by always asking in the QtDesigner
for  relative  values ... relative to some unit ... for example 10 units is
 the height of font which user thinks as normal size for him.
And    after  that  ask  ALL  sizes  in  QtDesigner  in  this units as
floats ... not an integer in pixels!
Including fonts ... so what it would not be in pt's ... because different
font  with  same  pt  looks smaller or larger.
How wonderful it would be if every font type with size 10 units in size is always
the same height as user thinks is comfortable for him!

After that this DPI problem will disappear ... as it does not matter how
big  is  pixel ... it matter how user feels about normal text size for
this  device. People with good eyes could hate this automatic High DPI
scale feature as they  could  feel OK with small elements which gives
them  more  info  on  screen. So if user does have High DPI screen and
needs  larger  sized  of all elements he just increases base-unit size
by 15%,  30%,  100% ... how he likes ... and have app's elements size
comfortable for him.

Do I miss something in this area or we still trying to solve the problem with
tricks   like   additional   integer   scale  factor and IN THE END we
again  will  face  users  which  do  not like size of elements we have
chosen for them !?

>Behind the scenes the new 5.6 support is actually a rewrite
If it is rewrite ... why not to start do it right.

> The user-visible changes are the environment variables:
>         QT_DEVICE_PIXEL_RATIO: deprecated, and replaced by
>         QT_SCALE_FACTOR: which takes a numeric scale factor, and
>         QT_AUTO_SCREEN_SCALE_FACTOR: (bool) reads the OS settings on X11 and Windows.
So   in   future   5.6  the  scale factor will be only integer ... 50%
larger will not be possible!

> There is no corresponding C++ API for applications at this point.
> One way around that is to call qputenv() as the very  first thing in main().
Why you start new things in this way? Start from hacks.
So   scale  factor  would  be  1) interger  and even ... 2) unchangeable ...

Why it is not possible to create global set-function which we can call
... only hacks?

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