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From c80564c1dfe202c3975ca0ff67e0b72b0352bf13 Mon Sep 17 00:00:00 2001
From: David Edmundson <davidedmundson@kde.org>
Date: Wed, 17 May 2023 09:06:03 +0300
Subject: [PATCH] Client: Always populate mimedata in drags
It's possible for clients to perform a drag and drop operation within
their own client without any mimeData. A user can directly access the
original drag.
On wayland without any mimedata it's impossible for a client to accept a
drag as the mechansim involved is to either select a given mimedata
entry or an empty string. Within Qt we always accept the first format if
we accept a drag.
When dragging within our own window we also start a wayland drag so will
receive a cancel event from the compositor if the compositor doesn't
believe the client has accepted the drag.
This patch provides a dummy mimedata entry so that something can be
accepted.
Fixes: QTBUG-112161
Pick-to: 6.6 6.5 6.2 5.15
Change-Id: I6309d82e20545e10ebdb9dafde7e13a5e3be5ff2
Reviewed-by: Liang Qi <liang.qi@qt.io>
(cherry picked from commit 32fedb6fa6579711b6cb192a2e3cfb7ad1264546)
* asturmlechner 2023-10-24: Backported L1 literal as QString::fromLatin1
---
src/client/qwaylanddatadevice.cpp | 6 ++++++
1 file changed, 6 insertions(+)
--- a/src/client/qwaylanddatadevice.cpp
+++ b/src/client/qwaylanddatadevice.cpp
@@ -124,6 +124,12 @@ bool QWaylandDataDevice::startDrag(QMimeData *mimeData, Qt::DropActions supporte
return false;
}
+ // dragging data without mimetypes is a legal operation in Qt terms
+ // but Wayland uses a mimetype to determine if a drag is accepted or not
+ // In this rare case, insert a placeholder
+ if (mimeData->formats().isEmpty())
+ mimeData->setData(QString::fromLatin1("application/x-qt-avoid-empty-placeholder"), QByteArray("1"));
+
m_dragSource.reset(new QWaylandDataSource(m_display->dndSelectionHandler(), mimeData));
if (wl_data_device_get_version(object()) >= 3)
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