1449793 - In cross-frame drag & drop, effectAllowed and dropEffect in dataTransfer are lost

Status: NEW

(Core :: DOM: Copy & Paste and Drag & Drop, defect, P3)

Description

[javascriptjedi]

Attachment: dragEvents.html

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Firefox/52.0
Build ID: 20180315163333

Steps to reproduce:

* Place attached HTML in web container, and then load it into two different Firefox windows
* Select and Drag & Drop text from blue box into red box in same window
Event.dataTransfer properties dropEffect and effectAllowed will correctly be logged to console as "copy"
* Select and Drag & Drop text from blue box into red box in the other window
Now dropEffect will be "move" and effectAllowed will be "uninitialized"

Note you MUST use a web container to reproduce this.  It won't reproduce if you load from local file using a file:/// URL.  I used a webcontainer with the port 8080.


Actual results:

dropEffect and effectAllowed fields of Event.transferData aren't what was stored in an actual cross-frame drag & drop


Expected results:

dropEffect and effectAllowed should both be "copy"

Note that this works in Firefox 52 ESR - so that you get "copy" for both properties in a cross-frame drag & drop.  It appears to have broken in FF 57.  I'm reporting it against FF59.

Comment 1

[javascriptjedi]

Note that, you can reproduce by opening the attachment above (where it says "attachment 8963431 [details]") in two Firefox windows.  Note how both properties are "copy" when you drag & drop inside the same window, but are "uninitialized" and "move" cross frame.

The actual drop itself may or may not fail - that's not what I'm reporting as a bug.  I'm reporting the wrong attributes in transferData in the dragOver() handler, *before* the mouse button is released.  You can actually reproduce without releasing the button over the target.

Comment 2

[javascriptjedi]

This may be a bug in the way the cross-origin rules are applied.  In the repro case, the two pages have the exact same URL, so you wouldn't think there would be any cross origin issue, right?  (As a test of that theory, one would simply have to install a plugin to disable cross-origin enforcement.)

Comment 3

[Stefan [:StefanG_QA]]

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0 (20180323154952)

I have tested and reproduced this issue using the steps above on Windows 10 with latest Nightly and Fx Release builds. When open the attachment in two windows I`m able to drag&drop between both windows. If I try to drag&drop in the same window I`m unable to do so. When doing so I can see the following entries in the browser:console:

DragOver: effectAllowed=copy, dropEffect=copy 
DragOver: effectAllowed=uninitialized, dropEffect=move


I think the right component for this report would be Core::Drag and Drop. Please change if this is not the right component.

Comment 4

[Neil Deakin]

Presumably, we aren't transfering the effectAllowed across to the child processes.