Fix WASM QT 6.9 by luadebug · Pull Request #7341 · xmake-io/xmake

luadebug · 2026-02-23T15:02:35Z

Resolves: #7340
Resolves: #7050

Test project stuff:
wasmrun.zip

Currently my approach requires to uncomment stuff. Although it looks like that stuff should be injected by XMake itself.

❯ cat ~/wasmrun/src/main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtPlugin>

// #ifdef Q_OS_WASM
// Q_IMPORT_PLUGIN(QWasmIntegrationPlugin)
// #endif

int main(int argc, char *argv[])
{
// #ifdef Q_OS_WASM
//     Q_INIT_RESOURCE(wasmwindow);
//     Q_INIT_RESOURCE(wasmfonts);
// #endif

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    const QUrl url(u"qrc:/qt/qml/qt_app/Main.qml"_qs);
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreationFailed,
        &app, []() { QCoreApplication::exit(-1); },
        Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

Aw I need really some good idea on how to fix/improve this.

find ~/wasmrun -name "static_import.cpp" | xargs cat
#include <QtPlugin>
Q_IMPORT_PLUGIN(QtQuickControls2BasicStyleImplPlugin)
Q_IMPORT_PLUGIN(QtQmlModelsPlugin)
Q_IMPORT_PLUGIN(QtQuick_WindowPlugin)
Q_IMPORT_PLUGIN(QtQmlPlugin)
Q_IMPORT_PLUGIN(QtQuickControls2BasicStylePlugin)
Q_IMPORT_PLUGIN(QtQuickControls2Plugin)
Q_IMPORT_PLUGIN(QtQuickLayoutsPlugin)
Q_IMPORT_PLUGIN(QtQuickControls2ImplPlugin)
Q_IMPORT_PLUGIN(QtQuickTemplates2Plugin)
Q_IMPORT_PLUGIN(QtQmlWorkerScriptPlugin)
Q_IMPORT_PLUGIN(QtQuick2Plugin)
Q_IMPORT_PLUGIN(QWasmIntegrationPlugin)
int init_qt_plugin_resources() {
    Q_INIT_RESOURCE(wasmwindow);
    Q_INIT_RESOURCE(wasmfonts);
    return 0;
}
static int s_init_qt_plugin_resources = init_qt_plugin_resources();

After last commit we get next to expected result without JavaScript flooding errors:

But the problem is now to optimize existing PR content, so yeah... help wanted be like.

gemini-code-assist · 2026-02-23T15:03:06Z

Summary of Changes

Hello @luadebug, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the build process and runtime compatibility for Qt applications targeting WebAssembly (WASM) using Xmake. It introduces optimizations for static plugin imports, updates Emscripten compiler flags to align with modern Qt 6.0+ requirements, and implements dynamic patching for generated HTML and JavaScript files to resolve common WASM-specific issues and enhance preload file support.

Highlights

Qt WASM Build Optimization: Optimized the generation of static_import.cpp for Qt plugins to prevent unnecessary file writes, improving build efficiency.
Emscripten Flag Updates: Enhanced Emscripten linker and shell flags for Qt 6.0+ WebAssembly (WASM) targets, including adjustments to exception handling, exported runtime methods, and exported functions for better compatibility and functionality.
Dynamic HTML and JavaScript Patching for WASM: Improved Qt WASM application deployment by dynamically patching wasm_shell.html and the generated JavaScript file to support preload files, address 'use strict' issues, and fix visualViewport access.
Static Plugin Loading for WASM: Enabled static plugin loading for Qt widget and quick applications when building for WebAssembly platforms, ensuring proper plugin integration.

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Changelog

xmake/rules/qt/load.lua
- Optimized the generation of static_import.cpp to only write the file if its content has changed, reducing redundant disk I/O.
- Updated Emscripten ldflags and shflags for Qt 6.0+ WASM builds, specifically changing DISABLE_EXCEPTION_CATCHING=1 to ASSERTIONS=0.
- Expanded the list of EXPORTED_RUNTIME_METHODS to include FS, callMain, cwrap, ccall, setValue, getValue, UTF8ToString, and stringToUTF8 for Qt 6.0+ WASM.
- Added _main, _malloc, and _free to EXPORTED_FUNCTIONS for Qt 6.0+ WASM builds.
xmake/rules/qt/xmake.lua
- Added logic to patch wasm_shell.html for Qt 6.0+ WASM builds, including support for preloadfiles and patching containerElements and qtContainerElements.
- Modified the generated .js file for Qt 6.0+ WASM to remove 'use strict'; directives to prevent runtime issues.
- Implemented a patch for this.visualViewport access in the generated .js file to handle undefined this context.
- Integrated static plugin configuration into qt.widgetapp and qt.quickapp rules when targeting WASM platforms, passing relevant plugins to the load function.

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gemini-code-assist

Code Review

This pull request introduces several improvements and fixes for Qt builds, particularly for the WebAssembly (Wasm) platform. The changes include optimizing file generation to avoid unnecessary writes, adding and updating Emscripten flags for newer Qt versions, and patching generated HTML and JavaScript files to fix compatibility issues. My review focuses on improving code maintainability by reducing duplication and suggesting structural improvements. Overall, these are valuable changes for enhancing Wasm support.

xmake/rules/qt/load.lua

xmake/rules/qt/xmake.lua

…target handling

…ng in load imports

luadebug · 2026-02-23T23:10:29Z

/gemini review

gemini-code-assist

Code Review

The pull request introduces necessary updates for Qt 6.9 WASM support, including static plugin resource initialization and essential patches for the Emscripten glue code. These changes address issues with selector handling and memory growth. I've suggested some improvements regarding the Emscripten flags and the efficiency of the file patching process.

xmake/rules/qt/load.lua

xmake/rules/qt/xmake.lua

xmake/rules/qt/load.lua

xmake/rules/qt/xmake.lua

…riting and copying only if different

…ogic

…scripten JS handling

…aintainability

xmake/rules/qt/build_qt_wasm_app.lua

waruqi · 2026-02-25T06:29:52Z

xmake/rules/qt/build_qt_wasm_app.lua

+                        i = i + 1
+                    end
+                    if content:sub(i, i) == ";" then i = i + 1 end
+                    local new_func = "var findCanvasEventTarget = target => {\n"


I'm not sure if there will be compatibility issues with this hard-coded JS code in Qt WASM.

我总是愿意等待，也许会有更好的选择出现。目前没有这个功能，它无法加载我在.zip 文件中提交的 QtQuick 应用。

…oved clarity and maintainability

luadebug added 4 commits February 23, 2026 01:53

Try repair QT behavior

e619f1e

Remove redundant debug prints from Qt WebAssembly rules

8990dc8

todo

8ed3f12

Merge branch 'xmake-io:dev' into em

3cf862e

luadebug marked this pull request as draft February 23, 2026 15:03

gemini-code-assist bot reviewed Feb 23, 2026

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luadebug changed the title Em Fix WASM QT 6.9 Feb 23, 2026

luadebug added 2 commits February 23, 2026 18:11

todo

c9f0816

Fix Emscripten JS issues for Qt WASM builds and enhance canvas event …

b8bcc5f

…target handling

luadebug marked this pull request as ready for review February 23, 2026 22:42

Refactor Qt WASM build configuration by removing unused plugin handli…

86a2b93

…ng in load imports

gemini-code-assist bot reviewed Feb 23, 2026

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Lazy fix to use .html instead of .js

e14d2b8

waruqi reviewed Feb 24, 2026

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luadebug added 4 commits February 25, 2026 00:20

Optimize import file handling by using a temporary file for content w…

6e697ce

…riting and copying only if different

Implement static plugin import file generation and refactor related l…

7c9dea1

…ogic

Refactor WASM app build logic into a separate function and enhance Em…

b54e056

…scripten JS handling

Refactor WASM app build logic into a separate Lua file for improved m…

284907f

…aintainability

luadebug requested a review from waruqi February 25, 2026 03:25

waruqi reviewed Feb 25, 2026

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Refactor Emscripten JS issue fixes into a dedicated function for impr…

6eeaf60

…oved clarity and maintainability

waruqi merged commit 27f49cd into xmake-io:dev Feb 25, 2026
35 of 37 checks passed

waruqi added this to the v3.0.8 milestone Feb 25, 2026

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luadebug commented Feb 23, 2026 •

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