How can I use WINRT c++ APIs in at Qt WINRT app?

Rad B · wrote on 25 Jun 2016, 05:34

Chris Kawa · 25 Jun 2016, 19:39

Well, depending on the approach it's either smooth ride or a horror show. Here's a "world of pain" type example that gets current date using WRL and puts it on a Qt's label:

#include <QApplication>
#include <QLabel>

#include <wrl/client.h>
#include <wrl/wrappers/corewrappers.h>
#include <windows.globalization.h>
#include <windows.globalization.datetimeformatting.h>

namespace WRL     = Microsoft::WRL;
namespace Wrap    = Microsoft::WRL::Wrappers;
namespace Fnd     = Windows::Foundation;
namespace ABIFnd  = ABI::Windows::Foundation;
namespace ABIGlob = ABI::Windows::Globalization;

auto format = L"{year.full}-{month.integer(2)}-{day.integer(2)}";

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QLabel lbl;
    lbl.setAlignment(Qt::AlignCenter);
    lbl.show();

    //Qt initializes COM for us so we don't need to call RoInitialize

    WRL::ComPtr<ABIGlob::ICalendar> calendar;
    Wrap::HStringReference calendarClassId(RuntimeClass_Windows_Globalization_Calendar);
    if (SUCCEEDED(Fnd::ActivateInstance(calendarClassId.Get(), calendar.GetAddressOf())))
    {
       ABIFnd::DateTime dateTime;
       if (SUCCEEDED(calendar->GetDateTime(&dateTime)))
       {
           WRL::ComPtr<ABIGlob::DateTimeFormatting::IDateTimeFormatterFactory> dateTimeFormatterFactory;
           Wrap::HStringReference dateTimeFormatterId(RuntimeClass_Windows_Globalization_DateTimeFormatting_DateTimeFormatter);
           if (SUCCEEDED(Fnd::GetActivationFactory(dateTimeFormatterId.Get(), dateTimeFormatterFactory.GetAddressOf())))
           {
               WRL::ComPtr<ABIGlob::DateTimeFormatting::IDateTimeFormatter> dateTimeFormatter;
               Wrap::HStringReference dateTimeFormat(format);
               if (SUCCEEDED(dateTimeFormatterFactory->CreateDateTimeFormatter(dateTimeFormat.Get(), dateTimeFormatter.GetAddressOf())))
               {
                   Wrap::HString formattedDateTime;
                   if (SUCCEEDED(dateTimeFormatter->Format(dateTime, formattedDateTime.GetAddressOf())))
                   {
                       uint buff_len;
                       auto buff = formattedDateTime.GetRawBuffer(&buff_len);

                       lbl.setText(QString::fromWCharArray(buff, buff_len));
                   }
               }
           }
       }
    }

    return a.exec();
}

And yes, before you manage to say "H O L Y F U U U ..." this is exactly the same as:

#include <QApplication>
#include <QLabel>
#include <QDate>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QLabel lbl(QDate::currentDate().toString("yyyy-MM-dd"));
    lbl.setAlignment(Qt::AlignCenter);
    lbl.show();

    return a.exec();
}

To spare yourself from going absolutely insane you might want to look into wrapper libraries like Modern.

Rad B · 29 Sept 2016, 13:30

@Chris-Kawa Thanks! I was actually hoping to use the HoloLens gestures as Qt has major problems with mouse and clicking on HoloLens. Or if Qt can be fixed I wouldn't have to.

I need to make the mouse follow and make clicking work on HoloLens. Like before Tuesday, haha!

hskoglund · wrote on 25 Jun 2016, 20:21

Hi, thanks @Chris-Kawa for that example!

Because I like to hurt myself I had to try it on my Windows 10 PC (worked fine).
Just want to add, if you want to run it as well, you need to add:

LIBS += -lruntimeobject

to your .pro file.

Edit: forgot to say: I tested with a vanilla Widgets app using the kit Desktop Qt 5.7.0 MSVC2015. However, if you instead select the Universal Windows Platform kit then that LIBS line above is not needed.

Chris Kawa · wrote on 25 Jun 2016, 21:28

As much as I hate language extensions it would probably be easier to use C++/CX. It would make the example not much longer than that with Qt, but I can't seem to enable it.
Passing /ZW and /AI <path to Platform.winmd> to the compiler (via QMAKE_CXXFLAGS in .pro file) should be enough AFAIK, but I get errors on as simple line as this:

String^ foo = ref new String(L"Hello");

error: C2664: 'long __winRT::__getActivationFactoryByPCWSTR(void *,Platform::Guid &,void **)': cannot convert argument 1 from 'const wchar_t []' to 'void *'
Probably some switch still missing somewhere...

hskoglund · wrote on 25 Jun 2016, 23:18

Hmm, never tried those pesky extensions, but being curious, I tried to reproduce your error but no luck :-( Maybe you're not on Windows 10 and MSVC2015?

I got it to run with your example above, by adding #include <qdebug.h> and these lines just before return a.exec(); at the end:

using namespace Platform;
String^ foo = ref new String(L"Hello");
qDebug() << QString::fromWCharArray(foo->Data());

I tested both the 5.7.0 Desktop MSVC2015 32-bit and the Universal Windows Platform kit.

And yeah, those /ZW and /AI switches (no space between /AI and dirname!) have to be in the .pro file:
QMAKE_CXXFLAGS += /ZW /AI\"C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcpackages\"

Chris Kawa · 26 Jun 2016, 00:27

@hskoglund said:

Maybe you're not on Windows 10 and MSVC2015?

I'm on Win10 and MSVC2015 with Qt5.7UWP. Yeah, sorry, I mixed up my tests. The string alone works indeed, but try this full example and you should see the errors:

#include <QApplication>
#include <QLabel>

using namespace Platform;
using namespace Windows::Globalization;
using namespace Windows::Globalization::DateTimeFormatting;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    auto calendar = ref new Calendar();
    auto dateTime = calendar->GetDateTime();
    String^ format = L"{year.full}-{month.integer(2)}-{day.integer(2)}";
    auto dateTimeFormatter = ref new DateTimeFormatter(format);
    auto formatted = dateTimeFormatter->Format(dateTime);

    QLabel lbl(QString::fromWCharArray(formatted->Data()));
    lbl.setAlignment(Qt::AlignCenter);
    lbl.show();

    return a.exec();
}

Rad B · wrote on 26 Jun 2016, 00:27

@Chris-Kawa @hskoglund

Great information, Thanks!

Unfortunately I don't think UWP HoloLens Gestures will work as it is 3D based and with a UWP app that's tough if not impossible. Well it would take some time and I have to have this project done before Tuesday. Probably not going to be possible.

Unless either of you know how to do this:
So the UWP apps are run in a container. Not sure if it is a Windows App Container or not but I want to be able to access the raw mouse & keyboard from the container level.

Thanks so much for your help!

hskoglund · wrote on 26 Jun 2016, 01:10

@Rad-B: Hi, I know games need to do this, and since some of them are UWP apps, raw mouse and keyboard access should be possible, for an example see stackoverflow

@Chris-Kawa: Indeed this time I got the errors (2 of them):
C:\Projects\untitled\main.cpp:23: error: C2664: 'long __winRT::__getActivationFactoryByPCWSTR(void *,Platform::Guid &,void **)': cannot convert argument 1 from 'const wchar_t [31]' to 'void *'

Googling a bit it seems this interesting error has struck more people than you (i.e you have not forgotten any switch or something similar).

So in conclusion I think this is a Monday morning bug and, while waiting for Microsoft to fix it (perhaps in Update 3?) you can always resort to a kludge, insert these fine lines of code just before int main(...:

HRESULT __stdcall GetActivationFactoryByPCWSTR(void*,Guid&, void**);
namespace __winRT
{
    HRESULT __stdcall __getActivationFactoryByPCWSTR(const void* str, ::Platform::Guid& pGuid, void** ppActivationFactory)
    {
        return GetActivationFactoryByPCWSTR(const_cast<void*>(str), pGuid, ppActivationFactory);
    }
}

This will cast away that const problem for you :-)

Chris Kawa · 27 Jun 2016, 07:54

@hskoglund Thanks for the workaround. I wonder how such a blatant bug could have slipped in :/

@Rad-B I don't have HoloLens so I can only speculate, but looking at the examples it doesn't seem to be that different from my calendar example, you just use the classes from the Windows::UI::Input::Spatial namespace. It seems the C++/CX is the easiest here, so you will probably have to use the workaround @hskoglund provided.
See here for some code examples (the SpatialInputHandler.h/.cpp files).

Rad B · wrote on 27 Jun 2016, 07:54

@Chris-Kawa @hskoglund How can I access Windows.UI.Core.CoreWindow?

namespace Windows::UI does not seem to work.

Thanks for both of your help!

mkalinow · R Rad B 25 Jun 2016, 19:39

@Rad-B Sorry for being a bit late to the discussion, but input on Hololens should have been fixed by https://codereview.qt-project.org/#/c/170653/ . At least we got feedback on JIRA, that this resolves input problems...

Chris Kawa · wrote on 16 Oct 2016, 09:58

Hey, good news! After years of begging Microsoft released a WinRT C++ library that doesn't suck like WRL: C++/WinRT

It's actually kinda simple to use. Close to Qt if not for the long names and namespaces. I gave it a whirl with the calendar example:

#include <QApplication>
#include <QLabel>
#include "winrt/Windows.Globalization.h"
#include "winrt/Windows.Globalization.DateTimeFormatting.h"

#pragma comment(lib, "windowsapp")
using namespace winrt::Windows::Globalization;
using namespace winrt::Windows::Globalization::DateTimeFormatting;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    std::wstring formatted = DateTimeFormatter(L"{year.full}-{month.integer(2)}-{day.integer(2)}").Format(Calendar().GetDateTime());

    QLabel lbl(QString::fromWCharArray(formatted.c_str()));
    lbl.setAlignment(Qt::AlignCenter);
    lbl.show();

    return a.exec();
}