https://bugs.kde.org/show_bug.cgi?id=398056
Andrew Crouthamel <andrew.croutha...@kdemail.net> changed:
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CC| |andrew.crouthamel@kdemail.n
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--- Comment #23 from Andrew Crouthamel <andrew.croutha...@kdemail.net> ---
(In reply to Fabian Vogt from comment #19)
> (In reply to Friedrich W. H. Kossebau from comment #15)
> > (In reply to Christoph Feck from comment #13)
> > > What exactly is the difference between Qt::AA_UseHighDpiPixmaps and
> > > Qt::AA_EnableHighDpiScaling, and should both be enabled for proper HiDPI
> > > support? Most applications I see only set the former property.
> >
> > Good question.
> > Not exactly sure, but I would bet both should be set for really good looking
> > UI currently for our legacy-based applications like KDevelop, which rely on
> > code done around low-dpi pixel sizes (think icon sizes referring to 16, 32
> > or 64 pixels per dimension), as still relied on in all(?) the QtWidget-based
> > KDE Frameworks modules.
> > From what I understood by reading the docs, Qt::AA_EnableHighDpiScaling
> > cares for scaling any QPainter commands and other pixel-based geometries.
> > While Qt::AA_UseHighDpiPixmaps makes sure that pixmaps which are rendered
> > for the unscaled pixel sizes are internally prepared for the real pixels
> > sizes when rendered in the end onto the real display.
> > But we indeed should consult some experts, not putting my hand here close to
> > any fire.
> >
> > (Adding fvogt as potential expoert to cc: list)
> > Fabian, can you tell more?
>
> It's complicated.
>
> QPainter etc. scale all the time, but by default the devicePixelRatio is 1 so
> it has no effect (except on OS X). All AA_EnableHighDpiScaling does is set
> the
> devicePixelRatio according to the DPI of the monitor the application is on.
>
> On Plasma on X11, where AA_EnableHighDpiScaling has no effect at all as it's
> overwritten using environment variables (QT_AUTO_SCREEN_SCALE_FACTOR and
> QT_SCREEN_SCALE_FACTORS).
>
> AA_UseHighDpiPixmaps is important as it allows QPixmap with a
> devicePixelRatio
> of > 1.
>
> So your guess is correct, both is the best option here.
>
> > (In reply to Saverio from comment #9)
> > > Oh, ok. Sorry, I didn't understand xD
> > > So, I'll wait other possible solutions, thanks anyway :)
> >
> > Saverio, as Kevin asked and linked, please test the Nigthly build of the
> > Windows version created after my commit. My fix was done as blind fix, just
> > done based on documentation and given it did not break things for me on my
> > lowdpi system :)
Should we start submitting patches to include both lines on all apps? Or is
there a list of "legacy" apps I could tackle?
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