1731622 - Dragging images across tabs/windows in the same process produces garbage

Status: VERIFIED FIXED

(Core :: DOM: Copy & Paste and Drag & Drop, defect, P2)

Description

[Tom S [:evilpie]]

When dragging an image in the same tab we produce a application/x-moz-nativeimage data item that contains an imgIContainer. However when dragging the same image across tabs/window (i.e. across content processes) we seem to "serialize" that data into a string and get absolute garbage.

Steps to reproduce:

• Open https://evercoder.github.io/clipboard-inspector/
• Open some new window with e.g. https://i.imgur.com/H3y8CxA.jpeg
• Drag the image in the inspector.

(Interestingly enough dragging the image across two different instances of Firefox actually works better, because we save the image to the native "drag service")

Comment 1

[Henri Sivonen (:hsivonen)]

On Linux, when dragging across instances of Firefox, I don't get image data at all. When dragging within an instance, application/x-moz-nativeimage indeed looks like garbage.

Mirko, can you, please, take a look?

Comment 2

[Tom S [:evilpie]]

So this happens because in the parent we call TransferablesToIPCTransferables in ContentParent::MaybeInvokeDragSession. TransferableToIPCTransferable will convert the imgIContainer used as data for application/x-moz-nativeimage to shmem.

In the child ContentChild::RecvInvokeDragSession we see IPCDataTransferData::TShmem and convert that to a simple string. This obviously isn't the correct behavior. We should actually use nsContentUtils::DataTransferItemToImage like IPCTransferableToTransferable does. Probably the correct fix here would be to to unify more of this code.

On Linux, when dragging across instances of Firefox, I don't get image data at all.

bug 1732528 and bug 1732526 should fix that. It should already work on Windows.

This does leave us in the somewhat weird situation where dragging images across different Firefox instances will work, but not in the same tab ...

Comment 3

[Mirko Brodesser (:mbrodesser-Igalia), offline until April 25h]

I wonder if this only affects Linux.

Comment 4

[Tom S [:evilpie]]

Attachment: Windows screenshot

I can reproduce this on a Windows VM. In the screenshot you can see two windows of the same Firefox instance. I dragged the image on the right to the clipboard inspector on the left.

Comment 5

[Alexandru Trif, Desktop QA [:atrif]]

Hello! I can reproduce the issue with Firefox 94.0a1, 93.0b9, 92.0.1, 91.1.0esr and 78.14.0esr. This happens on macOS 10.15 and Windows 10x64.
Also I searched for a regression range on Windows 10x64:
Last good revision: 5a4412474c63e1d9e66036d603ac42e9cb2b9150 (2017-01-23)
First bad revision: 8ff550409e1d1f8b54f6f7f115545dbef857be0b (2017-01-24)
Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=5a4412474c63e1d9e66036d603ac42e9cb2b9150&tochange=8ff550409e1d1f8b54f6f7f115545dbef857be0b

Comment 6

[Mirko Brodesser (:mbrodesser-Igalia), offline until April 25h]

Changing severity to S2 because non-minor functionality is impaired and no satisfactory workaround exists.

Comment 7

[Tom S [:evilpie]]

Attachment: Bug 1731622 - Handle images in ContentChild::RecvInvokeDragSession. r?nika

This is a copy of the similar code in RemoteDragStartData::AddInitialDnDDataTo

Comment 8

[Tom S [:evilpie]]

This patch "hides" the garbage from content JS, because we don't expose imgIContainer. However we really should expose some way to get the actual image data in a sane format like image/png.

Comment 9

[Nika Layzell [:nika] (ni? for response)]

(In reply to Tom Schuster [:evilpie] from comment #8)

This patch "hides" the garbage from content JS, because we don't expose imgIContainer. However we really should expose some way to get the actual image data in a sane format like image/png.

FWIW chrome also won't expose the raw image/png if you drag & drop an <img> tag into a drop area, it'll only expose 3 items: text/plain, text/uri-list and text/html, so this behaviour may be intentional. This is also the case if you drag an image from firefox into chrome or between two firefox instances.

Comment 10

[Tom S [:evilpie]]

FWIW chrome also won't expose the raw image/png if you drag & drop an <img> tag into a drop area, it'll only expose 3 items: text/plain, text/uri-list and text/html

Yeah, I noticed that as well. I wonder if that is intentional.

On windows dragging images from Firefox to Edge works, but not Edge to Firefox. Between two Firefox instances (different profiles) also works. However the default format of native clipboard data on Windows is BMP and not PNG.

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/93d9318f78d7
Handle images in ContentChild::RecvInvokeDragSession. r=nika

Comment 12

[Cristina Cozmuta (:CrissCozmuta)]

https://hg.mozilla.org/mozilla-central/rev/93d9318f78d7

Comment 13

[Cristian Fogel [:cfogel]]

Confirmed issue with 94.0a1 (2021-09-23), on Win10.
Fix verified with 94.0b2 on Win10 and Ubuntu 16x32.

Comment 14

[Mihai Boldan, Desktop QA [:mboldan]]

Based on Comment 13, I'm marking this issue as Verified Fixed.