[Development] High-dpi Qt best practices

[Samuel Rødal]

On 10/11/2012 10:16 AM, Sorvig Morten wrote:
>
> On Oct 11, 2012, at 9:36 AM, Samuel Rødal <samuel.rodal at digia.com>
>   wrote:
>
>> On 10/11/2012 08:23 AM, Ziller Eike wrote:
>>>
>>> On 10.10.2012, at 16:56, Olivier Goffart wrote:
>>>
>>> If you'd now be able to change the unit in Qt to "pixel metrics" for
>>> certain widgets (and optionally sub widgets) where you really want to
>>> take advantage of each and every pixel in e.g. painting code, then every
>>> case would be covered. (And you could decide to do what you suggest.)
>>
>> Agreed, it definitely needs to be possible to turn off the 2x2 scaling
>> for widgets that _do_ care about individual device pixels.
>
> How about:
>
> QPainter p(this);
> qreal scaleFactor = this->windowHandle()->dpiScaleFactor();
> p.scale(1.0 / scaleFactor, 1.0 / scaleFactor);
> QRect pxelRect(QPoint(0, 0), this->size() * scaleFactor);
> // paint within pxelRect
>
> A bit cumbersome, but it is a special case. Also, we need to make sure the call to scale cancel out properly with the 2x device scale and that the final transform has a proper QTransform::TransformationType .

That might be acceptable :)

--
Samuel