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

Rad B

Chris Kawa

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

@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

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

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

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

@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

@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

@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

@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

@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

@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

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();
}