Opening File Dialog crashes App using Qt for web assembly and emsdk with upstream backend

[DamienL]

Hi everyone,

I already asked this from here

Following the whole install process described here (thanks Lorn), I successully managed to get things to build fast...

I'm currently trying to access my local files from my application, as I saw it can be done using (cf "Slate" example, which I can build from QtCreator).

import Qt.labs.platform 1.0 as Platform
(...)

Platform.FileDialog {
        id: openProjectDialog
        objectName: "openProjectDialog"
        nameFilters: ["All files (*)", "JSON files (*.json)"]
        defaultSuffix: "json"
}

But I can't access my file/folder system, same when I build the Slate app. Both app crash, and the mozilla firefox console gives me this:

When I build simply the Qt source without the upstream backend (following Qt for web assembly wiki), even though it takes almost 15minutes to build and link, I manage to access my files from the browser with the Slate app.

(But my custom app only gives me this with the qt wiki build, but that's another post... or a quick answer, up to you ;) )

My config:

Qt 5.13.1
latest emsdk with upstream 1.39.0
macOS X Sierra 10.12.6
XCode clang :
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

The wasm-emscripten works fine during the Qt sources build, as it builds beautifully with em++/emcc.

Is it my setup limitation (llvm 8.00 ) ? I thought you didn't have to an up-to-date (or custom-built) version of llvm with the upstream build...

Thank you all.

[kuersat]

Having the same Problem here.
Could never access my own filesys. Theres got to be a solution to avoid the sandbox.

[DamienL]

Hello @kuersat , which problem ? Does it crash when you try to open a dialog with same config as me ?

Or do you have the same "lame" display in the dialog as shown in my post ?

[lorn.potter]

What you want is QFileDialog::getOpenFileContent
https://doc.qt.io/qt-5/qfiledialog.html#getOpenFileContent

All other QFileDialog functions will only access the sandbox filesystem.

Also you need to use this fork of slate:
https://github.com/msorvig/slate/tree/91114315b078680a7d40e41e805e8bb3a98c5815

[DamienL]

@lorn-potter

Thanks for the answer. I can now access my files but QFile can't open the json files I'm looking to process.

When using the getOpenFilenContent, I have this in the web browser console:

RuntimeError: unreachable executed qtloader.js line 270 > WebAssembly.compile:10489242:1

There is something I don't understand. Why could I build the Slate example, open files with the Qt Labs FileDialog and use QFile API, but now that I use emscripten I just can't... pretty frustrating.

Is there a work around to QFile to be able to parse/use local files in the browser ?

Thanks a lot.

[lorn.potter]

@DamienL
QFileDialog::getOpenFileContent is the workaround for accessing system/local files due to the javascript sandbox that webassembly lives in.