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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - wl_data_source should have an event to indicate completion of a drag session"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91944">91944</a>
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<th>Summary</th>
<td>wl_data_source should have an event to indicate completion of a drag session
</td>
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<th>Product</th>
<td>Wayland
</td>
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<th>Version</th>
<td>1.5.0
</td>
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<th>Hardware</th>
<td>x86-64 (AMD64)
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>wayland
</td>
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<th>Assignee</th>
<td>wayland-bugs@lists.freedesktop.org
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<th>Reporter</th>
<td>mcatanzaro@gnome.org
</td>
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<p>
<div>
<pre>When GTK+ is a drag source, it assumes that a drag session has ended after it
handles the data_source.send event. After handling data_source.send, it frees
memory associated with the drag session and releases its manual pointer grab,
causing data_offer.leave to be immediately sent to the destination client. This
causes several incompatibilities with the reference weston-dnd client:
* Unlike weston-dnd, it's impossible to send multiple different types of data
in the same session.
* This breaks Wayland clients that request transfer of data before the drop is
performed, which is well-supported by weston-dnd.
But GTK+ does this because anything else would be wrong: there is no other way
for the drag source to know when the drag session is over, other than to assume
that it ends during data_source.send. The weston-dnd client does not have these
issues because it has no need for a client-side grab (which must be released
when the DnD session is complete) and it simply leaks all memory associated
with the DnD sessions (<a class="bz_bug_link
bz_status_NEW "
title="NEW - weston-dnd leaks memory allocated in create_drag_icon()"
href="show_bug.cgi?id=91943">bug #91943</a>), which would be unacceptable for GTK+.
One way to fix this would be to add a new event, wl_data_source.drag_finished,
which the compositor would send to the source client at the same time it sends
wl_data_device.leave to the destination client. This has already been
implemented by Carlos Garnacho in [1] and [2], though it is just a subset of
the functionality added in those patches. GTK+ would then be modified to
release its grab in response to that event instead.
[1] <a href="http://lists.freedesktop.org/archives/wayland-devel/2015-June/022517.html">http://lists.freedesktop.org/archives/wayland-devel/2015-June/022517.html</a>
[2] <a href="http://lists.freedesktop.org/archives/wayland-devel/2015-June/022518.html">http://lists.freedesktop.org/archives/wayland-devel/2015-June/022518.html</a></pre>
</div>
</p>
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