[Interest] Widget to device pixel alignment under fractional DPI scaling

[Alvin Wong]

Dear all,

I have some questions on fractional DPI handling. I know fractional
DPI scaling isn't officially supported on Windows (waiting for
[QTBUG-53022][1] to be picked up again), but from what I hear KDE does
support actual fractional DPI scaling. Anyway, it is possible to test
fractional DPI on Windows with these environment variables (this
forces Qt to treat the first monitor as 1.5x scaling and the second
monitor as 1x), and does work kind of fine when it matches native
settings and using the Fusion style:

QT_AUTO_SCREEN_SCALE_FACTOR=0
QT_SCREEN_SCALE_FACTORS=1.5;1

I am trying to help get Krita to render the canvas in 1:1 device pixel
mapping. At this point it's certain that it can be made to work under
integer scaling (2x) but now I have some concerns on getting it to
work under fractional scaling (1.5x for example):

1. Does Qt align widgets positions to device pixels? In my
understanding, widget positions are specified in device-independent
pixels (I'll call it DIP for short), which can fall in between whole
device pixels. E.g. if a widget is at (31, 31) DIP, it would be placed
at (46.5, 46.5) px, which is at half pixels. Theoretically, painting a
0.6667 DIP line should result in a pixel-perfect 1px line, but will
this be broken due to the widget position not aligning to device
pixels?
2. Does Qt align widgets dimensions to device pixels? Like above, if a
widget has a width of 123 DIP, it would really be 184.5px. In this
case, and assuming that the left edge lies on a full device pixel,
what would happen to the right edge of the widget? And what if the
left edge is on half of a device pixel? Also, if an application wants
to create a pixel-perfect QBitmap (of devicePixelRatio=1, since the
aim is to paint in device pixels not DIP,) to be painted onto the
widget in full, what should its dimensions be?
3. On QOpenGLWidget: It creates the FBO in device pixels in
`QOpenGLWidgetPrivate::recreateFbo`, but with the code `const QSize
deviceSize = q->size() * q->devicePixelRatioF();` the FBO size is
implicitly truncated to integer. In
`QOpenGLWidgetPrivate::invokeUserPaint`, the OpenGL viewport
dimensions are also truncated to integer. Is there a possibility of
rounding errors, especially when the QOpenGLWidget is not using its
own native window?

The lowest Qt version we target is 5.9.x LTS if it makes any differences.

Best Regards,
Alvin

[1]: https://bugreports.qt.io/browse/QTBUG-53022
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[Interest] Sample Code for Apple TV and Apple Watch Qt Garage demos at Qt World Summit 2016

[Jeffrey Brendecke]

Would anyone know where I could find the sample code from these demos?

http://www.qtworldsummit.com/2016/discover-future-concepts-and-real-world-products-from-the-qt-garage/

Apple TV with Qt
– Apps & Multiplayer Games on iOS, Apple TB and Android by V-play

iOS and watchOS with Qt
– Displaying watch app controlling Qt 3D Planets over the local network


Sincerely,

Jeffrey Brendecke

Jeffrey Brendecke Software Services
Alt-Tegel 6
13507 Berlin
Germany

Tel: +49 151 4664-8751
Fax: +49 30 4309-3316‬
Email: jeffrey.brende...@gmail.com

VAT No: DE 301972289

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Re: [Interest] Sample Code for Apple TV and Apple Watch Qt Garage demos at Qt World Summit 2016

[Mike Krus via Interest]

> On 17 Oct 2018, at 12:52, Jeffrey Brendecke  
> wrote:
> 
> Would anyone know where I could find the sample code from these demos?
> 
> http://www.qtworldsummit.com/2016/discover-future-concepts-and-real-world-products-from-the-qt-garage/
> 
> Apple TV with Qt
> – Apps & Multiplayer Games on iOS, Apple TB and Android by V-play
> 
> iOS and watchOS with Qt
> – Displaying watch app controlling Qt 3D Planets over the local network
I believe this one is part of actual qt3d, although I can’t remember for sure 
if the patch was merged or not


Mike


> 
> Sincerely,
> 
> Jeffrey Brendecke
> 
> Jeffrey Brendecke Software Services
> Alt-Tegel 6
> 13507 Berlin
> Germany
> 
> Tel: +49 151 4664-8751
> Fax: +49 30 4309-3316‬
> Email: jeffrey.brende...@gmail.com
> 
> VAT No: DE 301972289
> 
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--
Mike Krus | mike.k...@kdab.com | Senior Software Engineer
KDAB (UK) Ltd., a KDAB Group company
Tel: UK Office +44 1625 809908   Mobile +44 7833 491941
KDAB - The Qt Experts, C++, OpenGL Experts



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Re: [Interest] Qt 5.12 Official packages for MinGW 64 bit?

[Kai Koehne]

> -Original Message-
> From: 黄其泽 
> Sent: Tuesday, October 16, 2018 9:58 AM
> To: Kai Koehne ; Qt Project 
> Subject: Re: [Interest] Qt 5.12 Official packages for MinGW 64 bit?
> 
> I heard that the upstream Chromium supports clang for windows. 

Indeed. Actually Chromium is using clang on all platforms.

> Will Qt
> official package provide clang version?

We've been discussing this already occasionally, but there's no immediate plan 
to switch to clang. See https://bugreports.qt.io/browse/QTBUG-4 for 
tracking 
this for WebEngine. Anyhow, we've mkspecs for clang (win32-clang-g++ and
win32-clang-msvc), so if somebody feels adventurous he can already give it a go 
😉
It's just that this is a configuration that we don't test internally, nor 
provide binaries
for.

One of the problems is that upstream Chromium is apparently not using a 
pristine 
Clang compiler, but a custom one. Also, it's unclear how this would work with 
other
Qt modules - would we have to build all of Qt with clang on Windows then,
or would the compilers be compatible enough? The latter one was the hope,
but until today it seems it doesn't even work for different MSVC compilers ...

Also, note that using Clang up to today still uses MSVC linker and SDK, so you
need both a MSVC installation and clang. So it's not a full replacement of e.g. 
MinGW.

Regards

Kai
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Re: [Interest] Qt 5.12 Official packages for MinGW 64 bit?

[Andy]

Thanks for the info Kai. That helps clarify the current state.

I'm now regretting using WebEngine. :-)

---
Andy Maloney  //  https://asmaloney.com
twitter ~ @asmaloney 



On Wed, Oct 17, 2018 at 8:28 AM Kai Koehne  wrote:

> > -Original Message-
> > From: 黄其泽 
> > Sent: Tuesday, October 16, 2018 9:58 AM
> > To: Kai Koehne ; Qt Project 
> > Subject: Re: [Interest] Qt 5.12 Official packages for MinGW 64 bit?
> >
> > I heard that the upstream Chromium supports clang for windows.
>
> Indeed. Actually Chromium is using clang on all platforms.
>
> > Will Qt
> > official package provide clang version?
>
> We've been discussing this already occasionally, but there's no immediate
> plan
> to switch to clang. See https://bugreports.qt.io/browse/QTBUG-4 for
> tracking
> this for WebEngine. Anyhow, we've mkspecs for clang (win32-clang-g++ and
> win32-clang-msvc), so if somebody feels adventurous he can already give it
> a go 😉
> It's just that this is a configuration that we don't test internally, nor
> provide binaries
> for.
>
> One of the problems is that upstream Chromium is apparently not using a
> pristine
> Clang compiler, but a custom one. Also, it's unclear how this would work
> with other
> Qt modules - would we have to build all of Qt with clang on Windows then,
> or would the compilers be compatible enough? The latter one was the hope,
> but until today it seems it doesn't even work for different MSVC compilers
> ...
>
> Also, note that using Clang up to today still uses MSVC linker and SDK, so
> you
> need both a MSVC installation and clang. So it's not a full replacement of
> e.g. MinGW.
>
> Regards
>
> Kai
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Re: [Interest] Sample Code for Apple TV and Apple Watch Qt Garage demos at Qt World Summit 2016

[Jeffrey Brendecke]

> On Oct 17, 2018, at 14:20, Mike Krus  wrote:
> 
>> 
>> On 17 Oct 2018, at 12:52, Jeffrey Brendecke > > wrote:
>> 
>> Would anyone know where I could find the sample code from these demos?
>> 
>> http://www.qtworldsummit.com/2016/discover-future-concepts-and-real-world-products-from-the-qt-garage/
>>  
>> 
>> 
>> Apple TV with Qt
>> – Apps & Multiplayer Games on iOS, Apple TB and Android by V-play
>> 
>> iOS and watchOS with Qt
>> – Displaying watch app controlling Qt 3D Planets over the local network
> I believe this one is part of actual qt3d, although I can’t remember for sure 
> if the patch was merged or not
> 
> 
> Mike
> 

Thanks, Mike!

Yes, everything appears to be there in the planets-qml example.

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[Interest] QVariant toString locale

[Etienne Sandré-Chardonnal]

Dear all,

I have a big table made of QVariants of many subtypes (dates, floats,
integers, etc...)
I need to output it in csv format with a user defined locale.

It seems, after searching the documentation for all possible ways:
 1) QTextStream can be set a locale, but it does not accepts QVariant
 2) QVariant has a toString method, but no custom locale can be used. The
documentation says nothing about the locale it uses, probably
QLocale::system() or QApplication::locale but maybe not.

So, I have to either:
 1) Handle all possible QVariant subtypes in a big switch block, I'd like
to avoid...
 2) Figure out if QVariant uses QApplication::locale(); change this locale,
do all the conversion, and restore QApplication::locale(), but this could
cause GUI flickers (as the GUI uses the app locale for display) and I would
rely on an undocumented assumption...

So as you see, it seems there is a hole in Qt's otherwise excellent
handling of locales. Am I wrong? Is there a good solution?

Best regards,

Etienne
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Re: [Interest] [Qt-creator] QtCreator 4.7.1 / Qt 5.12. Beta 1 (Android, iOS, macOS)

[Jason H]

Only if the iPhone 5C is not a target. It's the last ARM7 device, you'll need 5.9 for that.
 

Sent: Sunday, October 14, 2018 at 7:07 AM
From: ekke 
To: "interest@qt-project.org" , "qt-crea...@qt-project.org" 
Subject: Re: [Interest] [Qt-creator] QtCreator 4.7.1 / Qt 5.12. Beta 1 (Android, iOS, macOS)



found out from https://forum.qt.io/topic/95406/qt-5-12-beta-android-clang-app-crash

that NDK r16b is working for Android and Qt 5.12 Beta1

now I can build and deploy again on all my platforms with Qt 5.12B1 :)

Am 13.10.18 um 12:25 schrieb ekke:


I'm just testing Qt Creator 4.7.1 / Qt 5.12 Beta 1 with my QtQuickControls2 Apps for Android / iOS.

macOS also used, but only because testing is really fast on macOS

Xcode 10.0, macOS 10.13.6

---

macOS: getting warnings

Qt has only been tested with version 10.13 of the platform SDK, you're using 10.14.  This is an unsupported configuration. You may experience build issues, and by using the 10.14 SDK you are opting in to new features that Qt has not been prepared for. Please downgrade the SDK you use to build your app to version 10.13, or configure with CONFIG+=sdk_no_version_check when running qmake to silence this warning.

I'm still on macOS 10.13.6 and don't use any new things as dark mode.

seems to work

---

iOS: got some warning because my target was 10.0. Changed to 11.0:



QMAKE_IOS_DEPLOYMENT_TARGET = 11.0

now it works

BTW: got many warnings like this deploying the app to iOS device without changing deployment target to 11.0:

warning: object file (.../5.12.0/ios/lib/libQt5Core_debug.a(qglobal.o)) was built for newer iOS version (11.0) than being linked (10.0) 

so I expect we must use 11.0 ?

 

---

Android: currently I'm using NDK r10e

getting errors and cannot build:



Project ERROR: Cannot run target compiler 'android-ndk-r10e/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++'. Output:

===

/bin/sh: android-ndk-r10e/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++: No such file or directory

===

what's the recommended NDK to use with 5.12.Beta1 ?

seems that 5.12 Beta 1 now is using clang instead of GCC.

any other things to change in .pro ?

---

QML: some Pages now look different to 5.10.1 / 5.11.2 - per ex. Buttons placed different

probably because I have to fix some errors like:



"Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead."

(As I started Qt development for mobile I wasn't aware that anchors shouldn't be used inside Layouts,

so now I have to refactor ... fortunately QtCreator checks this now

hopefully this will fix the UI in 5.12 Beta 1 - if not will report an issue

 

 

ekke  

 
 

 
 

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[Interest] QML Input Handlers issues: any ideas on how to workaround https://bugreports.qt.io/browse/QTBUG-65795

[Alexander Ivash]

I haven't introduce that bug, but most likely I'm experiencing the
same behavior and would appreciate any ideas on workaround-ing it.

p.s. Especially from Shawn Rutledge
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Re: [Interest] QVariant toString locale

[Thiago Macieira]

On Wednesday, 17 October 2018 07:10:04 PDT Etienne Sandré-Chardonnal wrote:
>  1) Handle all possible QVariant subtypes in a big switch block, I'd like
> to avoid...
> 
> So as you see, it seems there is a hole in Qt's otherwise excellent
> handling of locales. Am I wrong? Is there a good solution?

Yeah, but our handling of QVariant is nowhere as good. That big switch is 
something we've also tried to avoid, but to the point that we know it's 
lacking and improperly done. There are a few updates for 5.12 that remove some 
of the old code, but nothing that would help you.

The light at the end of the tunnel is that you don't need to handle all types, 
only those that do get affected by the locale. That's usually those containing 
floating point. I'd handle those first in your conversion and everything else 
simply pass to QVariant::toString

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center



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Re: [Interest] Sample Code for Apple TV and Apple Watch Qt Garage demos at Qt World Summit 2016

[Christophe THOMAS]

Hello,

Pretty interested too in having some qt code running on an Apple Watch. My 
current understanding is that displaying something is hard and anyway qwidget 
and qml is not feasible?

Thx

Christophe

> Le 17 oct. 2018 à 14:38, Jeffrey Brendecke  a 
> écrit :
> 
> 
> 
>>> On Oct 17, 2018, at 14:20, Mike Krus  wrote:
>>> 
>>> 
>>> On 17 Oct 2018, at 12:52, Jeffrey Brendecke  
>>> wrote:
>>> 
>>> Would anyone know where I could find the sample code from these demos?
>>> 
>>> http://www.qtworldsummit.com/2016/discover-future-concepts-and-real-world-products-from-the-qt-garage/
>>> 
>>> Apple TV with Qt
>>> – Apps & Multiplayer Games on iOS, Apple TB and Android by V-play
>>> 
>>> iOS and watchOS with Qt
>>> – Displaying watch app controlling Qt 3D Planets over the local network
>> I believe this one is part of actual qt3d, although I can’t remember for 
>> sure if the patch was merged or not
>> 
>> 
>> Mike
>> 
> 
> Thanks, Mike!
> 
> Yes, everything appears to be there in the planets-qml example.
> 
> Jeffrey
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[Interest] Can't install Qt-5.11.2 on latest Windows 10

[Patrick Stinson]

Hello! I can’t seem to find any way to install qt-5.11.2 on Windows 10 from 
either the online installer or the all-in-one open source installer. Surely 
this isn’t happening for everyone?

I am getting installer errors as in this bug report:

https://bugreports.qt.io/browse/QTBUG-66853 


Does anyone know a workaround for this?

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Re: [Interest] Can't install Qt-5.11.2 on latest Windows 10

[Henry Skoglund]

On 17/10/2018 23.11, Patrick Stinson wrote:
Hello! I can’t seem to find any way to install qt-5.11.2 on Windows 10 
from either the online installer or the all-in-one open source 
installer. Surely this isn’t happening for everyone?


I am getting installer errors as in this bug report:

https://bugreports.qt.io/browse/QTBUG-66853

Does anyone know a workaround for this?

-Patric


Just guessing, but have you tried disabling your anti-virus program and 
then install Qt?


Rgrds Henry

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Re: [Interest] Issue with VirtualKeyboad and Wayland compositor.

[Christian Gagneraud]

On Wed, 17 Oct 2018 at 17:20, Christian Gagneraud  wrote:
>
> On Wed, 17 Oct 2018 at 13:51, Christian Gagneraud  wrote:
> >
> > I'm running the QtWayland 'pure-qml' example on an imx61 board with
> > linuxfb QPA, Qt-5.11.1 (I'm waiting for a 5.11.2 build).
> > I followed instructions from
> > http://doc.qt.io/qt-5/qtvirtualkeyboard-deployment-guide.html#using-qt-virtual-keyboard-with-qt-wayland.
> > The wayland client is the QtWidget's 'wiggly' example.
> >
> > When I click on the QLineEdit of Wiggly, the VKB pops up, but every
> > key i tap send QKeyEvent to wiggly, where the key code is always null
> > (zero).
>
> So i've run the same setup on Linux Desktop with Qt-5.11.1 and
> Qt-5.11.2 and it works as expected in both cases.
> I have as well enabled WAYLAND_DEBUG, and discovered that the problem
> lies somewhere b/w Qt VKB and QWaylandCompositor, here is a trace that
> show the lost of the key code:
>
> Logs from pure-qml:
> ...
> qt.virtualkeyboard: InputContextsendKeyClick(): 16777219
> [2541671.231] -> zwp_text_input_v2@14.keysym(0, 0, 1, 0)
> [2541671.480] -> zwp_text_input_v2@14.keysym(0, 0, 0, 0)
> ...
>
> Will investigate, to see the difference of wayland version b/w Linux
> Desktop and our custom embedded Linux distro.

After digging into QtWayland source code, it looks like a bug in
QtWayland, on Desktop it relies on Xkbcommon, on target it seems to
use native scan code, but implementation might not be fully
working/implemented.
Will create a bug report.

Chris

> Chris
>
>
> >
> > The key codes are correct on the wayland compositor side, from Qt logging:
> > qt.virtualkeyboard: InputEngine::virtualKeyPress(): Qt::Key(Key_O) "O"
> > QFlags(ShiftModifier) false
> > qt.virtualkeyboard: InputEngine::virtualKeyRelease(): Qt::Key(Key_O)
> > "O" QFlags(ShiftModifier)
> > qt.virtualkeyboard: InputContextsendKeyClick(): 79
> >
> > But from Wiggly (dumping QKeyEvent via eventFilter on the line edit):
> > QKeyEvent(KeyRelease, 0)
> > QKeyEvent(KeyPress, 0)
> > QKeyEvent(KeyRelease, 0)
> > QKeyEvent(KeyPress, 0)
> > QKeyEvent(KeyRelease, 0)
> >
> > All of the above is done with QtCreator:
> >
> > Wiggly is run with "-platform wayland" command line arguments and the
> > following 'Clean Run Environment':
> > QML2_IMPORT_PATH=/usr/lib/qt-5.11.1-imx61-shared/qml
> > QT_PLUGIN_PATH=/usr/lib/qt-5.11.1-imx61-shared/plugins
> > QT_QPA_PLATFORM=wayland
> > XDG_RUNTIME_DIR=/tmp
> >
> > pure-qml is run with "-platform linuxfb -plugin evdevtouch" command
> > line arguments and the following 'Clean Run Environment':
> > QML2_IMPORT_PATH=/usr/lib/qt-5.11.1-imx61-shared/qml
> > QT_IM_MODULE=qtvirtualkeyboard
> > QT_LOGGING_DEBUG=1
> > QT_LOGGING_RULES=qt.virtualkeyboard=true;qt.qpa.wayland*=true;
> > QT_PLUGIN_PATH=/usr/lib/qt-5.11.1-imx61-shared/plugins
> > QT_QPA_FB_DISABLE_INPUT=1
> > QT_QPA_FONTDIR=/usr/share/fonts
> > XDG_RUNTIME_DIR=/tmp
> > ___QML_IMPORT_TRACE=1
> > ___QT_DEBUG_PLUGINS=1
> >
> > Any idea about what is going on? As anyone successfully use such a setup?
> > Any tip on how to debug this further?
> >
> > Thanks,
> > Chris
> >
> > Notes:
> >
> > I have issues with udev and /dev/input, not sure if this can influence
> > the VKB. I'm currently waiting for a fix from our platform team.
> >
> > Full log from pure-qml:
> >
> > QIconvCodec::convertToUnicode: using Latin-1 for conversion, iconv_open 
> > failed
> > QIconvCodec::convertFromUnicode: using Latin-1 for conversion, iconv_open 
> > failed
> > Failed to open tty (No such device)
> > This plugin does not support createPlatformOpenGLContext!
> > QtCompositor: Failed to initialize EGL display. Could not get
> > EglDisplay for window.
> > qt.virtualkeyboard: InputContext::setLocale(): "en_GB"
> > qt.virtualkeyboard: PlatformInputContext::setLocale():
> > QLocale(English, Latin, UnitedKingdom)
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImInputItemClipRectangle)
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImInputItemClipRectangle)
> > qt.virtualkeyboard: PlatformInputContext::setFocusObject():
> > QQuickRootItem(0x80368)
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImQueryAll)
> > qt.virtualkeyboard: PlatformInputContext::commit()
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImInputItemClipRectangle)
> > qt.virtualkeyboard: PlatformInputContext::setFocusObject():
> > Chrome_QMLTYPE_4(0x321f98)
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImQueryAll)
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImEnabled|ImQueryInput)
> > qt.virtualkeyboard: InputContext::setFocus(): true
> > qt.virtualkeyboard: InputEngine::setInputMethod():
> > QtVirtualKeyboard::PlainInputMethod(0xa51e0)
> > qt.virtualkeyboard: InputEngine::setInputMode():
> > QtVirtualKeyboard::InputEngine::InputMode(Latin)
> > qt.virtualkeyboard: PlatformInputContext::reset()
> > qt.virtualkeyboard: PlatformInputContext::update():
> > QFlags(ImEnabled|ImMicr