Help regarding QRemoteObject.

Pradson

Hello,

I am using Qt C++ (Qt 5.12.3 version) for windows platform. I have developed an application which which renders on desktop. The same application I want to open in browser to view in web mode. I came to know regarding QRemoteObject which renders the application on desktop and web. I tried to seek some help regarding the same but unable to find it. Can anyone provide some help or a sample script on how to use this QRemoteObject?

Thankyou,

ChrisW67

To quote the docs, "Qt Remote Objects (QtRO) is an Inter-Process Communication (IPC) module". Nothing to do with rendering a desktop application in a web environment.

Pradson

@ChrisW67

Hi,
Thanks a lot for reply.

I think it could be possible to achieve the same with the combination of WebGL+QRemoteObject as mentioned in the below link-
https://www.develer.com/en/interact-with-a-qt-ui-from-any-browser/

I have tried to achieve the same with the help of below example link but I am unable to connect source replica signal currStateChanged() with client's recSwitchState() slot to receive source's current state. Whenever I run the same example application, then this "QObject::connect: No such signal SimpleSwitch::currStateChanged()" error message is appear in the console.

https://doc.qt.io/qt-5/remoteobjects-example-dynamic-replica.html

Kindly find the code section where I got the signal & slot connection error.

// Function to initialize connections between slots and signals
void DynamicClient::initConnection_slot()
{
    // connect source replica signal currStateChanged() with client's recSwitchState() slot to receive source's current state
   bool b1 = QObject::connect(reptr.data(), SIGNAL(currStateChanged()), this, SLOT(recSwitchState_slot()));
   
   // connect client's echoSwitchState(..) signal with replica's server_slot(..) to echo back received state
   bool b2 = QObject::connect(this, SIGNAL(echoSwitchState(bool)),reptr.data(), SLOT(server_slot(bool)));
}

If any more reference regarding the same, then kindly share.

Thanks,
Pradson

SGaist

Hi,

Aren't you looking for Qt for WebAssembly ?

Pradson

@SGaist

Hi,
Thanks for reply.

I am trying to interact with a Qt UI from any browser, for this I have tried the combination of WebGL+QRemoteObject as explained in the below link but I am facing runtime signal slot connection error as explained in the previous query. Do u have any idea regarding the same please share.
https://www.develer.com/en/interact-with-a-qt-ui-from-any-browser/

Regarding Qt for WebAssembly -
I need to describe some information regarding my product first. I am using C++/Qt5.12.3 and VisualStudio2017 compiler to build my product. I have used Qt widgets for UI as well.
Now I have few questions regarding Qt for WebAssembly-

Is Qt for WebAssembly capable to render Qtwidgets UI into web browser. If it is capable then with which version of Qt and VisualStudio complier?
Could I adopt it with my existing versions of the product (C++/Qt5.12.3 and VS2017 compiler)?
I have to go with VisualStudio Compiler. Can I adapt it easily with VS compiler?
Could you share me a sample example application code step by step of Qt for WebAssembly ( using C++/Qt widgets UI with VS compiler)?

Thankyou,
Pradson

SGaist

Yes, it can render widget based interfaces.
It does not use Visual Studio at all.
The versions supported are shown here.
As for demos, here you have starting page.

Pradson

@SGaist
Hi

Thanks a lot for prompt reply.

Please correct me-
I can not use the compiled binary of a Qt/C++ widgets application using VisualStudio Compiler for the Qt For WebAssembly ??? I think MinWG is supported for the same?

Is any road map plan to provide support for Visual Studio Compiler for the Qt For WebAssembly?

Thankyou,
Pradson

jsulm

@Pradson said in Help regarding QRemoteObject.:

I can not use the compiled binary of a Qt/C++ widgets application using VisualStudio Compiler for the Qt For WebAssembly ?

You can't.
As explained in https://doc.qt.io/qt-5/wasm.html you need emscripten as toolchain/compiler.
Whether Visual Studio Compiler will support WebAssembly in future is something you need to ask Microsoft.

Pradson

@jsulm

Hi,
Thanks for reply.

As you have shared me the link a saw about MinGW -
On Windows, make sure you have MinGW as well as sed in your PATH

My simple question was can I replace MinGW from VisualStudio to achieve the same?
(Or)
The Emscripten is enough for building Qt application and generating files for web?

Thanks & Regards,
Pradson

jsulm

@Pradson said in Help regarding QRemoteObject.:

My simple question was can I replace MinGW from VisualStudio to achieve the same?

I don't understand this question. Visual Studio does not have MinGW as far as I know.
MinGW is only needed if you want to build Qt by yourself. But do you want to do so? You can simply install prebuild Qt using Qt Online Installer.

Pradson

@jsulm
Hi,

Could you explain me the steps along with software required for the below mentioned case so that I could achieve the same?

I have created a calculator UI application in Qt Designer using Qt Widgets/C++. This calculator program is capable to run on desktop. How could I render it into web browser?

Thanks,
Pradson

jsulm

@Pradson

Install emscripten
Install Qt for WebAssembly (using Qt Online Installer or Qt Maintenance Tool)
Open your project in QtCreator
Build your project in QtCreator using the Kit for WebAssembly (this Kit is the one using emscripten as compiler and Qt for WebAssembly)

Pradson

@jsulm

I have installed emscripten but Qt for WebAssembly option is not available in the MaintenanceTool of the Qt5.15.10 LTS. I have attached screenshot herewith.

Kindly check and suggest.
Thanks,

jsulm

@Pradson Is it really all you see there? Usually you would for example also see Qt for MinGW. Is it offline installation?

Pradson

@jsulm

Hi,
Thanks a lot for reply.

I had installed Qt version "qt-enterprise-windows-x86-5.15.10" . It is offline installer. I can not go with MinGW, as I had told you earlier. I will have to prefer VisualStudio compiler (MSVC) because my current product is based on MSVC.

I would like to explain my requirement once again-
I have a product which is based on Qt5.15/C++. I am using MSVC binaries of Qt5.15. This means I have build my product using VisualStudio Compiler (MSVC). My product has QtWidgets UIs as well and I have to visualize those UIs in both desktop as well as in web. Is it possible using Qt for WebAssembly ? Is there any other method available?

**Please Note: ** I have to go with MSVC compiler.

Thanks,

jsulm

@Pradson If it is offline installer you will need to download offline installer for WebAssembly or use online installer. As commercial user you can also ask Qt Company for support.
I did not suggest to use MinGW, it was just an example for what you usually see in the maintenance tool...

Pradson

@jsulm

Hi,

As suggested, I have installed Qt5.15.10(MSVC2017 binaries) with all necessary packages including WebAssembly using online installer. I have create a sample QWidget UI application named "CalculatorOnWeb" and I am able to build successfully using the kit Qt 5.15.10 (msvc2019_64) . But when I select kit WebAssembly Qt 5.15.10, then getting errors-

Could not start process "mingw32-make.exe" -f C:/SE_CODE/Qt_related/QtForWebAssembly/CalculatorOnWeb/Makefile qmake_all.
Error while building/deploying project CalculatorOnWeb (kit: WebAssembly Qt 5.15.10)
When executing step "qmake"

Even when I tries to clean this project, then getting this error-

Could not start process "mingw32-make.exe" clean -j16.
Error while building/deploying project CalculatorOnWeb (kit: WebAssembly Qt 5.15.10)
When executing step "Make"

I have attached a screenshot herewith related to configuration of WebAssembly.

It is asking for MinGW and I can not go with MinGW as I had told you earlier. Please suggest about these errors.

Thanks,
Pradson

jsulm

@Pradson I don't use WebAssembly, so not sure. But it looks like for WebAssembly MinGW tool chain is used. So, try to install it via Qt Maintenance Tool. msvc2019_64 Qt has nothing to do with Qt for WebAssembly, it is for native Windows builds.

Pradson

@jsulm

Hi,
Thanks for prompt reply.

How will I install the WebAssembly MSVC tool chain ? I am unable to find the proper package from online installer. I am sharing the screenshot of MaintenanceTool. Please suggest which package is required to install.
Qt5.15.10_Packages-1.png

Qt5.15.10_Packages-2.png

Qt5.15.10_Packages-3.png

Thanks,
Pradson

jsulm

@Pradson I don't think there is such a thing as "WebAssembly MSVC tool chain". WebAssembly uses Enscrypten as compiler as far as I know, not MS VC++. SO, again: try to install MinGW (I mean only the tool chain not Qt for MinGW).

Please take a look at https://doc.qt.io/qt-5/wasm.html