Building RingQt Applications for WebAssembly

In this chapter we will learn about Building RingQt Applications for WebAssembly.

Download Requirements

Check the next link : https://doc.qt.io/qt-5/wasm.html

Tested using

emsdk install sdk-fastcomp-1.39.8-64bit
emsdk activate sdk-fastcomp-1.39.8-64bit

Check Emscripten installation

em++ --version

Output

emcc (Emscripten gcc/clang-like replacement) 1.39.8
(commit 24d88487f47629fac9d4acd231497a3a412bdee8)
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

  • Run Qt Creator

  • Select Tools > Options > Devices > WebAssembly

Qt for WebAssembly

Using Ring2EXE

We can use Ring2EXE to quickly prepare Qt project for our application

Example:

ring2exe myapp.ring -dist -webassemblyqt

Note

We can use the Distribute Menu in Ring Notepad

Tip

The option ( Prepare Qt project for WebAssembly ) in the Distribute Menu

Qt for WebAssembly shot1

The Qt project for your Ring application

After using Ring2EXE or the Distribute Menu in Ring Notepad

  • Using the Qt Creator Open the generated Qt project

    Folder : target/webassembly/qtproject

    Project file : project.pro

Qt for WebAssembly shot2

  • Using Qt Creator, You will find the compiled Ring application in the resources (YourAppName.ringo)

    This file (Ring Object File) is generated by the Ring compiler using

ring YourAppName.ring -go -norun

  • You can build your application using Qt Creator

Qt for WebAssembly shot3

The next screen shot for the application during the runtime

Qt for WebAssembly shot4

  1. You can add your application images to the resources

    Or You can use any text editor (Notepad) and modify : project.qrc

  2. To find images from your Ring application, You need to use the file name in resources

    Example

if isWebAssembly()
        mypic = new QPixmap(":/cards.jpg")
else
        mypic = new QPixmap("cards.jpg")
ok

Comments about developing for WebAssembly using RingQt

  1. The main project file is main.cpp

    This file load Ring Compiler/Virtual Machine and RingQt

    Then get the Ring Object File during the runtime from the resources

    Then run the Ring Object File (ringapp.ringo) using the Ring VM

    Through main.cpp you can extract more files from the resources to temp. folder once you add them (create projects with many files).

  2. use if isWebAssembly() when you want to modify the code just for WebAssembly

Example:

if isWebAssembly()
        // WebAssembly code
else
        // other platforms
ok

  1. When you deal with Qt Classes you can determine the images from resources (you don’t need to copy them using main.cpp)

Example:

if isWebAssembly()
    mypic = new QPixmap(":/cards.jpg")
else
    mypic = new QPixmap("cards.jpg")
ok

Now RingQt comes with the AppFile() function to determine the file name

Example:

mypic = new QPixmap(AppFile("cards.jpg"))  # Desktop, Android or WebAssembly

  1. When you update your project code, You don’t have to use Ring2EXE to generate the Qt project again

Just use the Distribute Menu in Ring Notepad and select (Generate Ring Object File)

Then copy the YourAppName.ringo file to target/webassembly/qtproject folder and accept replacing files.

  1. If your application folder contains a Qt resource file (project.qrc)

Then when you use Ring2EXE or Ring Notepad (Distribute - Prepare Qt project for WebAssembly) the resource file will be used

See ring/applications/cards game as an example.

  1. Use stdlibcore.ring instead of stdlib.ring when using StdLib functions

  2. Use ClocksPerSecond() function instead of typing the value (1000)

  3. Nested events loops are not supported, use events for dialogs instead of calling the exec() method

  4. Using Sleep() or ProcessEvents() doesn’t provide the expected results, use Qt Timers.

  5. We don’t have a direct access to the File System because the applications are executed in a secure environment

Tip

We can use special functions for Uploading/Downloading files (See FileContent sample)

Dialogs

See the folder: ring/samples/UsingQtWASM

Folders:

  • ColorDialog

  • FontDialog

  • FileDialog

  • FileContent