[Development] High-DPI 5.6 beta update

rpzrpzrpz at gmail.com rpzrpzrpz at gmail.com
Tue Dec 15 20:25:01 CET 2015

On 12/15/2015 5:03 AM, Sorvig Morten wrote:
> Hi,
> I’d like to provide short update on the changes in this space, an also lay out
> some plans and possibilities for the future. Thanks to everyone who has helped
> out! New changes:
> * @3x support landed, both for Qt Widgets and Qt Quick. Implemented as @Nx
>    support, with @9x as a maximum value.
> * The internal documentation for scaling in Qt has been updated:
>    github.com/qtproject/qtbase/blob/dev/src/gui/kernel/qhighdpiscaling.cpp.
> * Added C++ API for enabling/disabling high-dpi scaling:
>      Qt::AA_EnableHighDpiScaling
>      Qt::AA_DisableHighDpiScaling
>    Together with the environment variable (QT_AUTO_SCREEN_SCALE_FACTOR=1 or 0)
>    these provide comprehensive support for controlling whether scaling in Qt
>    should be enabled or not. Several use cases are supported:
>    * User wants to enable scaling (perhaps for “legacy” Qt apps):
>    * User wants disable scaling (there may be a hardware config issue):
>    * Developer wants to enable scaling:
>        Qt::AA_EnableHighDpiScaling
>    * Developer wants application to work in device pixels and disable scaling:
>        Qt::AA_DisableHighDpiScaling
>    In case of conflicts between the environment and C++ side the logic is ‘veto’.
>    The actual scale factor applied is controlled by the platform plugin, which
>    provides it by overriding QPlatformScreen::pixelDensity() The default
>    implementation returns 1. pixelDensity() is currently implemented by the
>    android, eglfs, windows, and xcb platform plugins.
> What’s next?
> 5.6 series:
> * Public overview documentation update.
> * Misc fixing in Widgets and Quick. In particular I would like to land a series of
>    GraphicsView fixes: https://codereview.qt-project.org/#/c/142920
> dev:
> * Improve support for fractional scale factors for QtWidgets (render at 2x and then
>    downscale). Will require OpenGL for the scaling. Prototype at
>    https://codereview.qt-project.org/143819 (OS X only).
> * Refactor qhighdpiscaling_h API and implementation:
>    https://codereview.qt-project.org/#/c/140176
> * Improve pixmap versioning support, replacing/extending @Nx and QIcon: QTBUG-49820
> * Figure out auto-testing: We can run entire tests at a given scale factor, or
>    individual test functions can test at a range of scale factors. Or we can do both.
>    We’ve so far relied on manual tests on actual high-dpi hardware. The cross-platform
>    scaling layer in Qt Gui now gives us the ability to auto test on any hardware
>    (including CI virtual hardware).
> If anyone is interested or has input on the above, drop me a note or comment on the
> mentioned task/changes.
> Thanks,
> Morten
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My comment only deals with vector graphics SVG formats QT.

Instead of worrying about @2x and @3x and trying to generate artwork in 
all of the sizes, would it not be advantageous
to only use SVG vector format and allow the svg plugin to generate and 
scale at run-time a single svg file in the QRC file instead of having to 
pre-generate files.

     id: gicon
     source: qrc:/img/test.svg
     anchors.fill: parent

Pro File:

QT += svg

Outside of the app, in the Android Manifext.xml and IOS, you need to 
provide pre-generated launcher PNG icons, but inside the app as well?

Your thoughts on projects that use ONLY SVG image resources and not 


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