Qt6.7 Drag and Drop on WebAssembly

PEPSoares

Hi,
I need a webassembly app that opens a file and uploads it's data to a CouchDb server via PUT.

Using QFileDialog::getOpenFileContent() I was able to this but the drawback is that I can only do it one file at a time.

Qt6.7 Now allows for Drag and drop events to be received.
I now received on the drop event something like [file:///qt/tmp/qebM8Nmr7Ok.jpg] which can be used as a source to a qml Image the problem is that I cannot use that source "qt/tmp/qebM8Nmr7Ok.jpg" to open a QFile. both QFile::exists() and open() return false;

 QFile *file = new QFile(path);
 qDebug() << "Exists "  << file->exists();  // always false

 //obviously fails since exists() returns false
 if(!file->open(QFile::ReadOnly)) 
  {
       qDebug() << "Error uploading file: " << path << file->error();  
       //error 5 QFileDevice::OpenError
}

Is this possible? Am I doing something wrong?

Christian Ehrlicher

@PEPSoares QFile takes a path, not an URL. Convert your URL to a path.

PEPSoares

@Christian-Ehrlicher ~
Thanks for replying
I am not using the URL on QFile I am converting it (I might be missing something......)

Here is a simple test.

//QML
 onDropped: function (drag) {
            var urls = drag.urls; 
            console.log("urls: ", urls) // urls:  [file:///qt/tmp/hrliUZNhpww.jpg]
            ...........

//cpp
.....
    qDebug() << "....." << fileUrl; // QUrl("file:////qt/tmp/hrliUZNhpww.jpg")
    qDebug() << "....." << fileUrl.path(); //  "//qt/tmp/hrliUZNhpww.jpg"
    qDebug() << "....." << fileUrl.fileName(); // "hrliUZNhpww.jpg"
    qDebug() << "....." << fileUrl.isLocalFile(); // true
    qDebug() << "....." << fileUrl.toLocalFile(); // "//qt/tmp/hrliUZNhpww.jpg"
    file2 = new QFile(fileUrl.path());
    qDebug() << "F2" << file2->exists(); // false
    qDebug() << "F2O" << file2->open(QFile::ReadOnly); // false
    file2 = new QFile(fileUrl.toLocalFile()); 
    qDebug() << "F2" << file2->exists(); // false
    qDebug() << "F2O" << file2->open(QFile::ReadOnly); // false
.....

Am I converting it wrong and sending the wrong path to QFIle?

Thanks

JonB

@PEPSoares said in Qt6.7 Drag and Drop on WebAssembly:

qDebug() << "....." << fileUrl.path(); // "//qt/tmp/hrliUZNhpww.jpg"

So you try to open //qt/tmp/hrliUZNhpww.jpg. I am not saying this is wrong, but the leading // is "unusual". You have not said what platform you are on. Can you see a directory accessible via //qt/tmp? Have you tried QFile("//qt/tmp/something") with exists() & open() to make sure that works?

PEPSoares

@JonB
Hi,
I know "//" might be wrong but I have no idea what the path should be...
I am on Qt6.7 WebAssembly multi-threaded.
I'll try to use QDir to check the path....

An image in Qml can access "file:////qt/tmp/hrliUZNhpww.jpg" so it must be there....

I am either sending the wrong path to QFile or QFile has no access to this dir the way I am using it.

I did not create that directory, from what I understand it was created by Qt or Emscripten temporally in the sandboxed filesystem..
For example, If you try to open a QFileDialog in web assembly you will see a sandbox filesystem product of emscripten...

PEPSoares

Well...... I guess I found the "problem".
QFile cannot open the file because the file does not exist....
I remembered to check with QFileDialog the sandbox filesystem.... there was a "qt" folder with a "tmp" but no file inside.

So how can qml Image access it?..... Apparently you can indeed set source: "received url" but only once.... if you do something like:

image.source = url;
lastUrl = url;

//wait some time 

image.source = "";
image.source = lastUrl;

Image will fail to open the url.

So...
How are files handled? They are copied but then immediately deleted? Is there any way I can control this?

Btw: QDir can access "/qt/tmp"

JonB

@PEPSoares said in Qt6.7 Drag and Drop on WebAssembly:

QFile cannot open the file because the file does not exist....

That does not surprise me. One would assume that the file is clearly a temporary file, valid somehow during the drag & drop, then removed. That is why I asked only if you could access the directory, not the file.

Btw: QDir can access "/qt/tmp"

The question was for //qt/tmp, not /qt/tmp.