Can't drag & drop files from desktop to browser (i.e. Google Drive)

[antoine132]

I have the same problem, also on Lubuntu. This problem appeared somewhat recently.
I have tried updating Firefox to the latest version, and also with a freshly installed Firefox-ESR (latest version), both from Mozilla's repository. This did not solve the problem.
Also, drag and dropping files works just fine on Chrome on the same machine.

What happens if you try opening the file in Firefox - put "file:///home/" in the address bar and find it.

It works for me, opens the file in browser as usual.

What type of installation is it (deb from Mozilla, deb from mozillateam PPA, tarball downloaded from Mozilla, flatpak,...)?

My original install was .deb through ubuntu repositories, then from Mozilla's repository. Neither worked.

Is any sand-boxing tools in play here? (firejail is one)

Something like this will show us what you have now:

apt policy firefox
firefox:
  Installed: 128.0.3~build1
  Candidate: 128.0.3~build1
  Version table:
     1:1snap1-0ubuntu6 500
        500 http://us.archive.ubuntu.com/ubuntu oracular/main amd64 Packages
 *** 128.0.3~build1 1000
       1000 https://packages.mozilla.org/apt mozilla/main amd64 Packages
        100 /var/lib/dpkg/status

This is what I get:

firefox:
  Installed: 128.0.3~build1
  Candidate: 128.0.3~build1
  Version table:
 *** 128.0.3~build1 500
        500 https://packages.mozilla.org/apt mozilla/main amd64 Packages
        100 /var/lib/dpkg/status
     128.0.2~build1 500
        500 https://packages.mozilla.org/apt mozilla/main amd64 Packages
     128.0+build2-0ubuntu0.20.04.1 500
        500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
     128.0~build2 500
        500 https://packages.mozilla.org/apt mozilla/main amd64 Packages
     127.0.2~build1 500
        500 https://packages.mozilla.org/apt mozilla/main amd64 Packages
(plus many more previous versions)

Hope this can help.

BTW,

That method works. i.e. If I right click a pdf on my desktop and choose "open with Firefox" it loads up in Firefox.
However, when I try and drag the pdf from my desktop into the Firefox window I get the red circle with a slash through beside my mouse pointer.

Unfortunately, for online services like Google Drive, the only way to upload files is to drag them from the desktop into the browser.

You can add a file to Google Drive by sending it to the associated Gmail address (if you have one), and then clicking the "add to Drive" icon on attached file in the email.

[#&thj^%]

I sandbox mine with firejail, and from my /Documents to drag goes like:

File not found

Firefox can’t find the file at /home/me/Documents/A Beginner's Guide to Editing Text Files With Vi.pdf.

    Check the file name for capitalization or other typing errors.
    Check to see if the file was moved, renamed or deleted.

Now if I copy that file to Downloads i get this, See screenshot.

[antoine132]

(Not OP, see my previous post)

Can you open about:support in Firefox and see what it says under Window Protocol?

It's x11 for me

[antoine132]

Here's another behaviour I observed:

I can switch focus from PCManFM to Firefox (FF) while dragging a file. I know that because I can navigate the toolbar bookmarks with the file as if it was a bookmark (while the cursor looks like this ). This is expected behaviour because you can do this with local files to bookmark them in FF. However, currently, I can only drag the file in the toolbar bookmarks; dropping it does nothing. It does not create a bookmark associated with the local file path as it should.

This is the only way I found to switch focus from PCManFM to FF while dragging a file. Dragging it to the address bar or on the web page is almost always met with this symbol : .

Turns out, while making this post, I observed that Imgur image uploader recognized I was trying to drop a file. It did not work, but it's the first time I've seen a web page exhibit this behaviour since my problem started.

[antoine132]

Welp, it seems it's a File Manager issue. My previously mentioned problems occured while using PCManFM, whereas everything works just fine with Caja.
I hope this can be of any help to anyone in the future.