[Interest] Changes in Qt 5.6 on Windows HiDPI

[Adam Light]

On Thu, Nov 12, 2015 at 3:49 PM, Adam Light <aclight at gmail.com> wrote:

> We've just started testing our application using Qt 5.6 (self built from
> Nov. 10 git checkout).
>
> It appears that the behavior of QDesktopWidget::logicalDpiX (and Y) has
> changed since Qt 5.5.
>
> We bought a Dell Inspiron 15 laptop with a High DPI display. If I open
> Control Panel, choose Display, and click the "set a custom scaling level"
> link, the scaling factor was set to 250% out of the box. When we run our
> application and call QApplication::desktop()->logicalDpiX(), the value
> returned is 80. Using Qt 5.5, that would have returned 240 (2.5 * 96).
>
> Is this change intentional? This change breaks a lot of the drawing code
> in our application, and so I'd like to know whether we need to adapt our
> application or if I should report this as a bug.
>
> Additionally, I notice that if I call
> QApplication::desktop()->devicePixelRatioF(), the returned value is 3. I
> would expect that 2.5 is returned.
>

For what it's worth, I've just created
https://bugreports.qt.io/browse/QTBUG-49465 for the devicePixelRatioF()
issue, since I'm pretty sure that's a bug.

Adam

>
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