How can i configure Qt Webassembly to use emscripten's file system api?

ratemal

Hi, want my app to use indexedDB to store data inetween sessions, and in order to use it i have to explicitly enable it inside emscripten configuration. However, i have no idea how to actually do that using QT. The documentation says i should use "-lidbfs.js" to enable it, but i don't know where exactly should i put that line. Can someone please advise me how to do that?

lorn.potter

Are you using qmake or cmake?

This presumes you have a javascript script that pre-mounts the filesystem, such as:
https://codereview.qt-project.org/c/qt/qtbase/+/301981/3/src/plugins/platforms/wasm/presettings.js

qmake, in your .pro file:

QMAKE_LFLAGS += -s FORCE_FILESYSTEM=1 --pre-js presettings.js -lidbfs.js

cmake, in CMakeFIles.txt:

target_link_libraries(<put target name here> PRIVATE idbfs.js)
target_link_options(<put target name here> PRIVATE --pre-js presettings.js)
target_link_options(<put target name here> PRIVATE "SHELL:-s FORCE_FILESYSTEM=1 ")

Change <put target name here> to what ever your apps 'target' name is.

ratemal

Thanks a lot for help, but something still seems to be working incorrectly. I am trying to use EM_ASM to use the code directly in my cpp file like this

EM_ASM(
            FS.mkdir('/src');
            FS.mount(IDBFS, {}, '/src');
            FS.syncfs(true, function (err) {
            });
        );

However, the project refuses to build due to "use of undeclared identifier FS", apparently not recognizing the macro for what it is. If i do it using the js script you mentioned, does it mean i will now be able to interact with "/home/web_user/.config" file normally using

file.open(QIODevice::ReadWrite);

Or is there some other way i can access it inside my code

lorn.potter

Maybe you need to add #include <emscripten.h>

Yes, that script is for QSettings, but you could put /src in there as well.