Qt for WebAssembly

AutoPlay and loops do not work in Qt 6.8.0/6.8.1. In 6.7.2, autoPlay is normal but there can only be one visible videooutput. Loops does not work either. In addition, your wasm must set the source externally, such as after clicking a button or "Component.onCompleted" . mediaPlayer.source = "xxx.mp3" Also, even if you only play audio, it seems that you need to set videoOutput, and since 6.7.3, there may be memory problems when using loader and mediaplayer. So it's better to avoid using mediaplayer.

Hi,

I have the same problem. Have developen a qt widget webasm application on qt 6.8 where the main annoyance right now is this problem.

If browser windows is lesser than the default widget size it will not adjust to the browser window unless browser window is resized just so little it adjusts just fine to the size. It is like it fails to read the browser size when layout the main window.

on 2 dec. 2024, I asked that question again and someone gave me an answer, see https://forum.qt.io/topic/159970/using-qsvggenerator-with-webassembly

@jsulm Thank you, I try that ASAP.

It works fine either on Desktop and Wasm. Now I need to plug my data.

void MainWindow::exporter() { QSvgGenerator SG; SG.setSize(QSize(200, 200)); SG.setViewBox(QRect(0, 0, 200, 200)); SG.setTitle(tr("SVG Generator Example Drawing")); SG.setDescription(tr("An SVG drawing created by the SVG Generator " "Example provided with Qt.")); QPainter painter; QBuffer buffer; SG.setOutputDevice(&buffer); painter.begin(&SG); painter.end(); QFileDialog::saveFileContent(buffer.data(), "myExport.svg"); }

By using

tf = QFont("Bitstream Vera Sans", 8); tf.setLetterSpacing(QFont::AbsoluteSpacing, -1);

I almost have the same rendering, except a small vertical offset that I can correct, My alignment formula is using an absolute value and I need to change it to relative.

@Birk-Skyum Thanks - this prompted me to try with the multithreaded Qt 6.8 version and (once I enable SharedArrayBuffer in Chrome) it solves the issue in Windows. Looks like I'll have to compile two versions for the forseeable future...)

I amost got it, now I only need to press TAB after I clicked on a new color to be able to use keyboard shortcuts to rotate my 3d model. It breaks the working flow, but is usable. I'm using code (on the cellpress event handler of my TableWidget) to try to give the focus to my GraphicsView, but on WASM it doesn't seem to do anything. To be able to have the selected row showing the row color instead of its negative, I needed to add a label widget and add it to the first cell of the row, I added noTextInteraction to its TextInteractionFlags otherwise it has the focus when I click on it and handle keystrokes. Is there anything I can do ? is it possible to send a TAB keystroke at the end of my code so that the user doesn't need to do it ?

ui->tableCouleurs->releaseKeyboard(); ui->vue3d->setFocus(Qt::OtherFocusReason);

Capture d'écran 2024-11-17 151222.png

I also tried with -DQT_DEBUG_FIND_PACKAGE=ON and the output is

CMake Error at CMakeLists.txt:16 (find_package): Found package configuration file: /Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake/Qt6/Qt6Config.cmake but it set Qt6_FOUND to FALSE so package "Qt6" is considered to be NOT FOUND. Reason given by package: Failed to find required Qt component "BuildInternals". Expected Config file at "/Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake/Qt6BuildInternals/Qt6BuildInternalsConfig.cmake" exists Configuring with --debug-find-pkg=Qt6BuildInternals might reveal details why the package was not found. find_package search path values and other context for the last package that was not found: CMAKE_MODULE_PATH: /Users/boyankiovtorov/emsdk/upstream/emscripten/cmake/Modules;/Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake/Qt6;/Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake/Qt6/3rdparty/extra-cmake-modules/find-modules;/Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake/Qt6/3rdparty/kwin CMAKE_PREFIX_PATH: $ENV{CMAKE_PREFIX_PATH}: CMAKE_FIND_ROOT_PATH: /Users/boyankiovtorov/emsdk/upstream/emscripten/cache/sysroot;/Users/boyankiovtorov/emsdk/upstream/emscripten/cache/sysroot;/Users/boyankiovtorov/emsdk/upstream/emscripten/cache/sysroot;/Users/boyankiovtorov/emsdk/upstream/emscripten/cache/sysroot;/Users/boyankiovtorov/emsdk/upstream/emscripten/cache/sysroot _qt_additional_packages_prefix_paths: _qt_additional_host_packages_prefix_paths: _qt_cmake_dir: /Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake QT_HOST_PATH: /Users/boyankiovtorov/Qt/6.8.0 Qt6HostInfo_DIR: /Users/boyankiovtorov/Qt/6.8.0/macos/lib/cmake/Qt6HostInfo Qt6_DIR: /Users/boyankiovtorov/Qt/6.8.0/wasm_singlethread/lib/cmake/Qt6 CMAKE_TOOLCHAIN_FILE: /Users/boyankiovtorov/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake CMAKE_FIND_ROOT_PATH_MODE_PACKAGE: ONLY CMAKE_SYSROOT: $ENV{PATH}: /Library/Frameworks/Python.framework/Versions/3.12/bin:/opt/homebrew/opt/libiodbc/bin:/Users/boyankiovtorov/emsdk:/Users/boyankiovtorov/emsdk/upstream/emscripten:/Library/Frameworks/Python.framework/Versions/3.12/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/X11/bin:/Library/Apple/usr/bin:/Applications/VMware Fusion.app/Contents/Public:/usr/local/share/dotnet:~/.dotnet/tools:/Users/boyankiovtorov/Library/Application Support/JetBrains/Toolbox/scripts:/usr/local/mysql/bin

@JonB At first I tried to run Wasm using asyncify parameter but it didn't change anything. I suspect that there are others things that are not fitted for Wasm, for example, click on a ToolBar ToolButton that opens a popup menu make Wasm crash, just like right click to open a context menu. I'm still hoping that there's a way to do those things with Wasm as common ways don't work. For the moment I'm simply putting my actions on ToolBars.

@jsulm My problem was that I had a Qt project from 2 years ago that compiled for WAsm and now has errors (linking errors). It was a QMake project and I converted it to CMake so that now it compiles again. Thank you.

Well, you can't argue with results. Embedding the font as you suggested worked perfectly. Thank you for the suggestion!

@JonB Yup that is me. It works just fine. He probably just used .exec() which will cause the application to crash without asyncify. You should use .show() instead.

@Pradson "How shall I enable the "Access-Control-Allow-Origin" header at my QHttpSever module?" E.g.:

QHttpServer httpServer; httpServer.route("/", []() { QHttpServerResponse sr("Hello World!"); QHttpHeaders&& hd = sr.headers(); hd.append(QHttpHeaders::WellKnownHeader::AccessControlAllowOrigin, "http://localhost:30000"); sr.setHeaders(std::move(hd)); return sr; });

Now I checked under 6.8 and it works again. :-)

I have tried enabling asynchronous, increasing initialization memory, and adjusting the maximum memory, but all have no effect. It is random and the browser console cannot capture useful errors. Sometimes it is memory access out of bounds at .wasm.QQuickDeliveryAgentPrivate:: Sometimes isUncaught RuntimeError: null function or function signature mismatch
at .wasm.QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) It is also possible that there is only uncaught

Qt/Quick does not know how to handle Blob resources. You can either use a normal url, or pack in in a Qt resource file.

@alihitman99
What is the error message?

Amazing. Thank you very much, this really works.
True, I didn’t understand where in your link to look at the correspondence between the versions of emscripten and Qt, but if you build using version emscripten 3.1.50 with Qt 6.7, then everything works fine. This is the first webassembly application in my life ;-)