Seat correctly emits dragEnded when a DataSourceInterface is destroyed,
and stops the drag.
However WlToXSource lives slightly longer to finish handling any other
visits. See the guarded delete statement in Dnd::endDrag.
With recent fixes use is mostly a hypothetical, but we still don't want
dangling pointers in our code.
The main advantage of SPDX license identifiers over the traditional
license headers is that it's more difficult to overlook inappropriate
licenses for kwin, for example GPL 3. We also don't have to copy a
lot of boilerplate text.
In order to create this change, I ran licensedigger -r -c from the
toplevel source directory.
Summary:
Building upon the generic X Selection support this patch establishes another
selection class representing the XDND selection and provides interfaces
to communicate drags originating from Xwayland windows to the Wayland
server KWin and drags originating from Wayland native drags to Xwayland.
For Wayland native drags KWin will claim the XDND selection as owner and
will simply translate all relevant events to the XDND protocol and receive
alike messages by X clients.
When an X client claims the XDND selection KWin is notified via the X protocol
and it decides if it allows the X drag to transcend into the Wayland protocol.
If this is the case the mouse position is tracked and on entering a Wayland
native window a proxy X Window is mapped to the top of the window stack. This
proxy window acts as a drag destination for the drag origin window and again
X messages will be translated into respective Wayland protocol calls. If the
cursor leaves the Wayland window geometry before a drop is registered, the
proxy window is unmapped, what triggers a subsequent drag leave event.
In both directions the necessary core integration is minimal. There is a single
call to be done in the drag and drop event filter through the Xwayland
interface class.
From my tests this patch facilitates drags between any Qt/KDE apps. What needs
extra care are the browsers, which use target formats, that are not directly
compatible with the Wayland protocol's MIME representation. For Chromium an
additional integration step must be done in order to provide it with a net
window stack containing the proxy window.
Test Plan: Manually. Auto tests planned.
Reviewers: #kwin
Subscribers: zzag, kwin, alexde
Tags: #kwin
Maniphest Tasks: T4611
Differential Revision: https://phabricator.kde.org/D15627
