client: Implement qt-toplevel-drag-v1

This protocol for tabs toolbars and dock widgets to be dragged in and
out of a main window using an extended version of the drag and drop
protocol. Application code in QtBase use a special internal mimedata to
specify a window that should be associated with a drag.

This is 1:1 match with the pending upstream proposal xdg-toplevel-drag,
and can be switched when that lands.

Change-Id: Idf0afb71cd98d45938b4641ce861484fffac911c
Reviewed-by: David Edmundson <davidedmundson@kde.org>

6 files changed, 146 insertions, 12 deletions

diff --git a/src/3rdparty/protocol/qt-toplevel-drag-v1.xml b/src/3rdparty/protocol/qt-toplevel-drag-v1.xml
new file mode 100644
index 000000000..72a22cbbd
--- /dev/null
+++ b/src/3rdparty/protocol/qt-toplevel-drag-v1.xml
@@ -0,0 +1,83 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="qt_toplevel_drag_v1">
+
+  <copyright>
+    Copyright 2022 David Redondo  &lt;kde@david-redondo.de&gt;
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice (including the next
+    paragraph) shall be included in all copies or substantial portions of the
+    Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+  </copyright>
+
+  <interface name="qt_toplevel_drag_manager_v1" version="1">
+  <description summary="Move a window during a drag">
+    This protocol enhances normal drag and drop with the ability to move a
+    window at the same time. This allows having detachable windows that
+    can also be reattached when dragged back to another window or some special
+    zone.
+
+    Warning! The protocol described in this file is currently in the testing
+    phase. Backward compatible changes may be added together with the
+    corresponding interface version bump. Backward incompatible changes can
+    only be done by creating a new major version of the extension.
+  </description>
+
+    <request name="get_qt_toplevel_drag">
+      <description summary="get an qt_toplevel_drag for a wl_data_source">
+        Create an qt_toplevel_drag for a drag and drop operation that is going
+        to be started with data_source.
+        This request can only be made on sources used in drag-and-drop, so it
+        must be performed before wl_data_device.start_drag. Attempting to use
+        the source other than for drag-and-drop will raise an invalid_source error.
+      </description>
+      <arg name="id" type="new_id" interface="qt_toplevel_drag_v1"/>
+      <arg name="data_source" type="object" interface="wl_data_source"/>
+    </request>
+
+    <request name="release" type="destructor" />
+
+    <enum name="error">
+      <entry name="invalid_source" value="0" summary="data_source already used for toplevel drag"/>
+    </enum>
+  </interface>
+
+  <interface name="qt_toplevel_drag_v1" version="1">
+    <description summary="Object representing a toplevel move during a drag">
+    </description>
+
+    <request name="attach">
+      <description summary="Move a toplevel with the drag operation">
+        Request that the window will be moved with the cursor during the drag operation. The offset
+        describes how the toplevel will be positioned relative to the cursor hotspot
+        in surface local coordinates.
+        Issuing this request after the drag has ended will result in a drag_ended protocol error.
+      </description>
+      <arg name="toplevel" type="object" interface="xdg_toplevel" />
+      <arg name="x_offset" type="int" summary="dragged surface x offset"/>
+      <arg name="y_offset" type="int" summary="dragged surface y offset"/>
+    </request>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy an qt_toplevel_drag object" />
+    </request>
+
+    <enum name="error">
+      <entry name="drag_ended" value="0" summary="corresponding drag has ended" />
+    </enum>
+  </interface>
+</protocol>
diff --git a/src/client/CMakeLists.txt b/src/client/CMakeLists.txt
index d42259fc0..4fab5b319 100644
--- a/src/client/CMakeLists.txt
+++ b/src/client/CMakeLists.txt
@@ -93,6 +93,8 @@ qt6_generate_wayland_protocol_client_sources(WaylandClient
         ${CMAKE_CURRENT_SOURCE_DIR}/../3rdparty/protocol/xdg-output-unstable-v1.xml
         ${CMAKE_CURRENT_SOURCE_DIR}/../3rdparty/protocol/fractional-scale-v1.xml
         ${CMAKE_CURRENT_SOURCE_DIR}/../3rdparty/protocol/viewporter.xml
+        ${CMAKE_CURRENT_SOURCE_DIR}/../3rdparty/protocol/qt-toplevel-drag-v1.xml
+        ${CMAKE_CURRENT_SOURCE_DIR}/../3rdparty/protocol/xdg-shell.xml
         ${CMAKE_CURRENT_SOURCE_DIR}/../extensions/qt-key-unstable-v1.xml
         ${CMAKE_CURRENT_SOURCE_DIR}/../extensions/qt-text-input-method-unstable-v1.xml
         ${CMAKE_CURRENT_SOURCE_DIR}/../extensions/qt-windowmanager.xml
diff --git a/src/client/qwaylanddatadevice.cpp b/src/client/qwaylanddatadevice.cpp
index a7014f7a1..e9d82100f 100644
--- a/src/client/qwaylanddatadevice.cpp
+++ b/src/client/qwaylanddatadevice.cpp
@@ -13,6 +13,8 @@
 #include "qwaylandabstractdecoration_p.h"
 #include "qwaylandsurface_p.h"
 
+#include <QtWaylandClient/private/qwayland-qt-toplevel-drag-v1.h>
+
 #include <QtCore/QMimeData>
 #include <QtGui/QGuiApplication>
 #include <QtGui/private/qguiapplication_p.h>
@@ -27,6 +29,8 @@ QT_BEGIN_NAMESPACE
 
 namespace QtWaylandClient {
 
+using namespace Qt::StringLiterals;
+
 QWaylandDataDevice::QWaylandDataDevice(QWaylandDataDeviceManager *manager, QWaylandInputDevice *inputDevice)
     : QObject(inputDevice)
     , QtWayland::wl_data_device(manager->get_data_device(inputDevice->wl_seat()))
@@ -105,14 +109,47 @@ bool QWaylandDataDevice::startDrag(QMimeData *mimeData, Qt::DropActions supporte
                 drag->setResponse(response);
             }
     });
-    connect(m_dragSource.data(), &QWaylandDataSource::dndDropped, this, [](bool accepted, Qt::DropAction action) {
-        QPlatformDropQtResponse response(accepted, action);
-        static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag())->setDropResponse(response);
-    });
-    connect(m_dragSource.data(), &QWaylandDataSource::finished, this, []() {
+    connect(m_dragSource.data(), &QWaylandDataSource::dndDropped, this,
+            [this](bool accepted, Qt::DropAction action) {
+                QPlatformDropQtResponse response(accepted, action);
+                if (m_toplevelDrag) {
+                    // If the widget was dropped but the drag not accepted it
+                    // should be its own window in the future. To distinguish
+                    // from canceling mid-drag the drag is accepted here as the
+                    // we know if the widget is over a zone where it can be
+                    // incorporated or not
+                    response = { accepted, Qt::MoveAction };
+                }
+                static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag())
+                        ->setDropResponse(response);
+            });
+    connect(m_dragSource.data(), &QWaylandDataSource::finished, this, [this]() {
         static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag())->finishDrag();
+        if (m_toplevelDrag) {
+            m_toplevelDrag->destroy();
+            m_toplevelDrag = nullptr;
+        }
     });
 
+    if (mimeData->hasFormat("application/x-qt-mainwindowdrag-window"_L1)
+        && m_display->xdgToplevelDragManager()) {
+        qintptr dockWindowPtr;
+        QPoint offset;
+        QDataStream windowStream(mimeData->data("application/x-qt-mainwindowdrag-window"_L1));
+        windowStream >> dockWindowPtr;
+        QWindow *dockWindow = reinterpret_cast<QWindow *>(dockWindowPtr);
+        QDataStream offsetStream(mimeData->data("application/x-qt-mainwindowdrag-position"_L1));
+        offsetStream >> offset;
+        if (auto waylandWindow = static_cast<QWaylandWindow *>(dockWindow->handle())) {
+            if (auto toplevel = waylandWindow->surfaceRole<xdg_toplevel>()) {
+                m_toplevelDrag = new QtWayland::qt_toplevel_drag_v1(
+                        m_display->xdgToplevelDragManager()->get_qt_toplevel_drag(
+                                m_dragSource->object()));
+                m_toplevelDrag->attach(toplevel, offset.x(), offset.y());
+            }
+        }
+    }
+
     start_drag(m_dragSource->object(), origin->wlSurface(), icon->wlSurface(), m_display->currentInputDevice()->serial());
     return true;
 }
@@ -148,7 +185,6 @@ void QWaylandDataDevice::data_device_drop()
     QPlatformDropQtResponse response = QWindowSystemInterface::handleDrop(m_dragWindow, dragData, m_dragPoint, supportedActions,
                                                                           QGuiApplication::mouseButtons(),
                                                                           QGuiApplication::keyboardModifiers());
-
     if (drag) {
         auto drag =  static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag());
         drag->setDropResponse(response);
@@ -175,16 +211,14 @@ void QWaylandDataDevice::data_device_enter(uint32_t serial, wl_surface *surface,
     QDrag *drag = static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag())->currentDrag();
     if (drag) {
         dragData = drag->mimeData();
-        supportedActions = drag->supportedActions();
     } else if (m_dragOffer) {
         dragData = m_dragOffer->mimeData();
         supportedActions = m_dragOffer->supportedActions();
     }
 
-    const QPlatformDragQtResponse &response = QWindowSystemInterface::handleDrag(m_dragWindow, dragData, m_dragPoint, supportedActions,
-                                                                                 QGuiApplication::mouseButtons(),
-                                                                                 QGuiApplication::keyboardModifiers());
-
+    const QPlatformDragQtResponse &response = QWindowSystemInterface::handleDrag(
+            m_dragWindow, dragData, m_dragPoint, supportedActions, QGuiApplication::mouseButtons(),
+            QGuiApplication::keyboardModifiers());
     if (drag) {
         static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag())->setResponse(response);
     }
@@ -263,6 +297,10 @@ void QWaylandDataDevice::dragSourceCancelled()
 {
     static_cast<QWaylandDrag *>(QGuiApplicationPrivate::platformIntegration()->drag())->finishDrag();
     m_dragSource.reset();
+    if (m_toplevelDrag) {
+        m_toplevelDrag->destroy();
+        m_toplevelDrag = nullptr;
+    }
 }
 
 QPoint QWaylandDataDevice::calculateDragPosition(int x, int y, QWindow *wnd) const
diff --git a/src/client/qwaylanddatadevice_p.h b/src/client/qwaylanddatadevice_p.h
index 76c8965f9..b924aa7ef 100644
--- a/src/client/qwaylanddatadevice_p.h
+++ b/src/client/qwaylanddatadevice_p.h
@@ -31,6 +31,10 @@ class QMimeData;
 class QPlatformDragQtResponse;
 class QWindow;
 
+namespace QtWayland {
+class qt_toplevel_drag_v1;
+}
+
 namespace QtWaylandClient {
 
 class QWaylandDisplay;
@@ -93,8 +97,8 @@ private:
     QScopedPointer<QWaylandDataOffer> m_dragOffer;
     QScopedPointer<QWaylandDataOffer> m_selectionOffer;
     QScopedPointer<QWaylandDataSource> m_selectionSource;
-
     QScopedPointer<QWaylandDataSource> m_dragSource;
+    QtWayland::qt_toplevel_drag_v1 *m_toplevelDrag = nullptr;
 };
 
 }
diff --git a/src/client/qwaylanddisplay.cpp b/src/client/qwaylanddisplay.cpp
index c49cb428a..ae066beca 100644
--- a/src/client/qwaylanddisplay.cpp
+++ b/src/client/qwaylanddisplay.cpp
@@ -53,6 +53,7 @@
 #include <QtWaylandClient/private/qwayland-fractional-scale-v1.h>
 #include <QtWaylandClient/private/qwayland-viewporter.h>
 #include <QtWaylandClient/private/qwayland-cursor-shape-v1.h>
+#include <QtWaylandClient/private/qwayland-qt-toplevel-drag-v1.h>
 
 #include <QtCore/private/qcore_unix_p.h>
 
@@ -758,6 +759,9 @@ void QWaylandDisplay::registry_global(uint32_t id, const QString &interface, uin
         mViewporter.reset(new QtWayland::wp_viewporter(registry, id, qMin(1u, version)));
     } else if (interface == QLatin1String(QtWayland::wp_cursor_shape_manager_v1::interface()->name)) {
         mCursorShapeManager.reset(new QtWayland::wp_cursor_shape_manager_v1(registry, id, std::min(1u, version)));
+    } else if (
+            interface == QLatin1String(QtWayland::qt_toplevel_drag_manager_v1::interface()->name)) {
+        mXdgToplevelDragManager.reset(new QtWayland::qt_toplevel_drag_manager_v1(registry, id, 1));
     }
 
     mGlobals.append(RegistryGlobal(id, interface, version, registry));
diff --git a/src/client/qwaylanddisplay_p.h b/src/client/qwaylanddisplay_p.h
index 877ff9692..7a64749ef 100644
--- a/src/client/qwaylanddisplay_p.h
+++ b/src/client/qwaylanddisplay_p.h
@@ -54,6 +54,7 @@ namespace QtWayland {
     class wp_cursor_shape_manager_v1;
     class wp_fractional_scale_manager_v1;
     class wp_viewporter;
+    class qt_toplevel_drag_manager_v1;
 }
 
 namespace QtWaylandClient {
@@ -154,6 +155,7 @@ public:
     QtWayland::wp_fractional_scale_manager_v1 *fractionalScaleManager() const { return mFractionalScaleManager.data(); }
     QtWayland::wp_viewporter *viewporter() const { return mViewporter.data(); }
     QtWayland::wp_cursor_shape_manager_v1 *cursorShapeManager() const { return mCursorShapeManager.data();}
+    QtWayland::qt_toplevel_drag_manager_v1 *xdgToplevelDragManager() const { return mXdgToplevelDragManager.data();}
 
     struct RegistryGlobal {
         uint32_t id;
@@ -280,6 +282,7 @@ private:
     QScopedPointer<QtWayland::wp_viewporter> mViewporter;
     QScopedPointer<QtWayland::wp_fractional_scale_manager_v1> mFractionalScaleManager;
     QScopedPointer<QtWayland::wp_cursor_shape_manager_v1> mCursorShapeManager;
+    QScopedPointer<QtWayland::qt_toplevel_drag_manager_v1> mXdgToplevelDragManager;
     int mFd = -1;
     int mWritableNotificationFd = -1;
     QList<RegistryGlobal> mGlobals;