xdgforeign: Allow exporting surfaces internally

Without a client asking for it. This way we can send a surface
to another helper application, such as the window killer.

An ExportedSurface wrapper class is introduced which represents
an exported surface in a windowing-system independent way.

src/wayland/xdgforeign_v2.cpp

@@ -1,6 +1,7 @@
 /*
     SPDX-FileCopyrightText: 2017 Marco Martin <notmart@gmail.com>
     SPDX-FileCopyrightText: 2021 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
+    SPDX-FileCopyrightText: 2023 Kai Uwe Broulik <kde@broulik.de>
 
     SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
 */
@@ -15,6 +16,29 @@ namespace KWin
 static const quint32 s_exporterVersion = 1;
 static const quint32 s_importerVersion = 1;
 
+XdgExportedSurface::XdgExportedSurface(SurfaceInterface *surface)
+    : QObject()
+    , m_handle(QUuid::createUuid().toString())
+    , m_surface(surface)
+{
+    connect(m_surface, &QObject::destroyed, this, &XdgExportedSurface::handleSurfaceDestroyed);
+}
+
+QString XdgExportedSurface::handle() const
+{
+    return m_handle;
+}
+
+SurfaceInterface *XdgExportedSurface::surface() const
+{
+    return m_surface;
+}
+
+void XdgExportedSurface::handleSurfaceDestroyed()
+{
+    delete this;
+}
+
 XdgForeignV2InterfacePrivate::XdgForeignV2InterfacePrivate(Display *display, XdgForeignV2Interface *_q)
     : q(_q)
     , exporter(new XdgExporterV2Interface(display, _q))
@@ -37,17 +61,38 @@ SurfaceInterface *XdgForeignV2Interface::transientFor(SurfaceInterface *surface)
     return d->importer->transientFor(surface);
 }
 
+XdgExportedSurface *XdgForeignV2Interface::exportSurface(SurfaceInterface *surface)
+{
+    return d->exporter->exportSurface(surface);
+}
+
 XdgExporterV2Interface::XdgExporterV2Interface(Display *display, XdgForeignV2Interface *foreign)
     : QObject(foreign)
     , QtWaylandServer::zxdg_exporter_v2(*display, s_exporterVersion)
 {
 }
 
-XdgExportedV2Interface *XdgExporterV2Interface::exportedSurface(const QString &handle)
+XdgExportedSurface *XdgExporterV2Interface::exportedSurface(const QString &handle) const
 {
     return m_exportedSurfaces.value(handle);
 }
 
+XdgExportedSurface *XdgExporterV2Interface::exportSurface(SurfaceInterface *surface)
+{
+    auto *exported = new XdgExportedSurface(surface);
+    addExported(exported);
+    return exported;
+}
+
+void XdgExporterV2Interface::addExported(XdgExportedSurface *exported)
+{
+    const QString handle = exported->handle();
+    connect(exported, &XdgExportedSurface::destroyed, this, [this, handle] {
+        m_exportedSurfaces.remove(handle);
+    });
+    m_exportedSurfaces[handle] = exported;
+}
+
 void XdgExporterV2Interface::zxdg_exporter_v2_destroy(Resource *resource)
 {
     wl_resource_destroy(resource->handle);
@@ -68,15 +113,9 @@ void XdgExporterV2Interface::zxdg_exporter_v2_export_toplevel(Resource *resource
     }
 
     XdgExportedV2Interface *exported = new XdgExportedV2Interface(surface, exportedResource);
-    const QString handle = QUuid::createUuid().toString();
+    addExported(exported);
 
-    // a surface not exported anymore
+    exported->send_handle(exported->handle());
-    connect(exported, &XdgExportedV2Interface::destroyed, this, [this, handle]() {
-        m_exportedSurfaces.remove(handle);
-    });
-
-    m_exportedSurfaces[handle] = exported;
-    exported->send_handle(handle);
 }
 
 XdgImporterV2Interface::XdgImporterV2Interface(Display *display, XdgForeignV2Interface *foreign)
@@ -110,7 +149,7 @@ void XdgImporterV2Interface::zxdg_importer_v2_import_toplevel(Resource *resource
 
     // If there is no exported surface with the specified handle, we must still create an
     // inert xdg_imported object and send the destroyed event right afterwards.
-    XdgExportedV2Interface *exported = m_foreign->d->exporter->exportedSurface(handle);
+    XdgExportedSurface *exported = m_foreign->d->exporter->exportedSurface(handle);
     if (!exported) {
         auto imported = new XdgDummyImportedV2Interface(importedResource);
         imported->send_destroyed();
@@ -175,15 +214,9 @@ void XdgImporterV2Interface::unlink(XdgImportedV2Interface *parent, SurfaceInter
 }
 
 XdgExportedV2Interface::XdgExportedV2Interface(SurfaceInterface *surface, wl_resource *resource)
-    : QtWaylandServer::zxdg_exported_v2(resource)
+    : XdgExportedSurface(surface)
-    , m_surface(surface)
+    , QtWaylandServer::zxdg_exported_v2(resource)
 {
-    connect(surface, &QObject::destroyed, this, &XdgExportedV2Interface::handleSurfaceDestroyed);
-}
-
-SurfaceInterface *XdgExportedV2Interface::surface()
-{
-    return m_surface;
 }
 
 void XdgExportedV2Interface::zxdg_exported_v2_destroy(Resource *resource)
@@ -196,11 +229,6 @@ void XdgExportedV2Interface::zxdg_exported_v2_destroy_resource(Resource *resourc
     delete this;
 }
 
-void XdgExportedV2Interface::handleSurfaceDestroyed()
-{
-    delete this;
-}
-
 XdgDummyImportedV2Interface::XdgDummyImportedV2Interface(wl_resource *resource)
     : QtWaylandServer::zxdg_imported_v2(resource)
 {
@@ -216,11 +244,11 @@ void XdgDummyImportedV2Interface::zxdg_imported_v2_destroy_resource(Resource *re
     delete this;
 }
 
-XdgImportedV2Interface::XdgImportedV2Interface(XdgExportedV2Interface *exported, wl_resource *resource)
+XdgImportedV2Interface::XdgImportedV2Interface(XdgExportedSurface *exported, wl_resource *resource)
     : QtWaylandServer::zxdg_imported_v2(resource)
     , m_exported(exported)
 {
-    connect(exported, &QObject::destroyed, this, &XdgImportedV2Interface::handleExportedDestroyed);
+    connect(exported, &XdgExportedSurface::destroyed, this, &XdgImportedV2Interface::handleExportedDestroyed);
 }
 
 SurfaceInterface *XdgImportedV2Interface::child() const

src/wayland/xdgforeign_v2.h

@@ -16,6 +16,23 @@ class Display;
 class SurfaceInterface;
 class XdgForeignV2InterfacePrivate;
 
+class KWIN_EXPORT XdgExportedSurface : public QObject
+{
+    Q_OBJECT
+
+public:
+    XdgExportedSurface(SurfaceInterface *surface);
+
+    QString handle() const;
+    SurfaceInterface *surface() const;
+
+private:
+    void handleSurfaceDestroyed();
+
+    const QString m_handle;
+    SurfaceInterface *m_surface;
+};
+
 /**
  * This class encapsulates the server side logic of the XdgForeign protocol.
  * a process can export a surface to be identifiable by a server-wide unique
@@ -39,6 +56,13 @@ public:
      */
     SurfaceInterface *transientFor(SurfaceInterface *surface);
 
+    /**
+     * Exports the given surface without creating a Wayland interface object.
+     * @param surface The surface to export
+     * @return The handle, this can then be passed to other clients.
+     */
+    XdgExportedSurface *exportSurface(SurfaceInterface *surface);
+
 Q_SIGNALS:
     /**
      * A surface got a new imported transient parent

src/wayland/xdgforeign_v2_p.h

@@ -1,6 +1,7 @@
 /*
     SPDX-FileCopyrightText: 2017 Marco Martin <notmart@gmail.com>
     SPDX-FileCopyrightText: 2021 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
+    SPDX-FileCopyrightText: 2023 Kai Uwe Broulik <kde@broulik.de>
 
     SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
 */
@@ -11,6 +12,8 @@
 
 #include <qwayland-server-xdg-foreign-unstable-v2.h>
 
+#include <QPointer>
+
 namespace KWin
 {
 class XdgExportedV2Interface;
@@ -35,14 +38,17 @@ class XdgExporterV2Interface : public QObject, public QtWaylandServer::zxdg_expo
 public:
     XdgExporterV2Interface(Display *display, XdgForeignV2Interface *foreign);
 
-    XdgExportedV2Interface *exportedSurface(const QString &handle);
+    XdgExportedSurface *exportedSurface(const QString &handle) const;
+    XdgExportedSurface *exportSurface(SurfaceInterface *surface);
 
 protected:
     void zxdg_exporter_v2_destroy(Resource *resource) override;
     void zxdg_exporter_v2_export_toplevel(Resource *resource, uint32_t id, wl_resource *surface) override;
 
 private:
-    QHash<QString, XdgExportedV2Interface *> m_exportedSurfaces;
+    void addExported(XdgExportedSurface *exported);
+
+    QHash<QString, XdgExportedSurface *> m_exportedSurfaces;
 };
 
 class XdgImporterV2Interface : public QObject, public QtWaylandServer::zxdg_importer_v2
@@ -67,24 +73,16 @@ private:
     QHash<XdgImportedV2Interface *, SurfaceInterface *> m_children; // parent->child hash
 };
 
-class XdgExportedV2Interface : public QObject, public QtWaylandServer::zxdg_exported_v2
+class XdgExportedV2Interface : public XdgExportedSurface, public QtWaylandServer::zxdg_exported_v2
 {
     Q_OBJECT
 
 public:
     explicit XdgExportedV2Interface(SurfaceInterface *surface, wl_resource *resource);
 
-    SurfaceInterface *surface();
-
 protected:
     void zxdg_exported_v2_destroy(Resource *resource) override;
     void zxdg_exported_v2_destroy_resource(Resource *resource) override;
-
-private Q_SLOTS:
-    void handleSurfaceDestroyed();
-
-private:
-    SurfaceInterface *m_surface;
 };
 
 class XdgDummyImportedV2Interface : public QtWaylandServer::zxdg_imported_v2
@@ -101,7 +99,7 @@ class XdgImportedV2Interface : public QObject, QtWaylandServer::zxdg_imported_v2
 {
     Q_OBJECT
 public:
-    explicit XdgImportedV2Interface(XdgExportedV2Interface *exported, wl_resource *resource);
+    explicit XdgImportedV2Interface(XdgExportedSurface *exported, wl_resource *resource);
 
     SurfaceInterface *child() const;
     SurfaceInterface *surface() const;
@@ -113,7 +111,7 @@ private Q_SLOTS:
     void handleExportedDestroyed();
 
 private:
-    XdgExportedV2Interface *m_exported;
+    XdgExportedSurface *m_exported;
     QPointer<SurfaceInterface> m_child;
 
 protected:

src/wayland_server.cpp

@@ -510,6 +510,11 @@ SurfaceInterface *WaylandServer::findForeignTransientForSurface(SurfaceInterface
     return m_XdgForeign->transientFor(surface);
 }
 
+XdgExportedSurface *WaylandServer::exportAsForeign(SurfaceInterface *surface)
+{
+    return m_XdgForeign->exportSurface(surface);
+}
+
 void WaylandServer::initWorkspace()
 {
     auto inputPanelV1Integration = new InputPanelV1Integration(this);

src/wayland_server.h

@@ -36,6 +36,7 @@ class PlasmaVirtualDesktopManagementInterface;
 class PlasmaWindowManagementInterface;
 class OutputDeviceV2Interface;
 class OutputManagementV2Interface;
+class XdgExportedSurface;
 class XdgForeignV2Interface;
 class XdgOutputManagerV1Interface;
 class DrmClientBufferIntegration;
@@ -153,6 +154,11 @@ public:
      */
     SurfaceInterface *findForeignTransientForSurface(SurfaceInterface *surface);
 
+    /**
+     * Exports a surface with the foreign protocol
+     */
+    XdgExportedSurface *exportAsForeign(SurfaceInterface *surface);
+
     /**
      * @returns file descriptor for Xwayland to connect to.
      */