Implement parent_window handling on Wayland

On Wayland the compositor can be informed about the semantic relationships
between the windows via the xdg_foreign protocol.

src/utils.cpp

@@ -6,6 +6,8 @@
 
 #include "utils.h"
 
+#include "waylandintegration.h"
+
 #include <KWindowSystem>
 
 #include <QSettings>
@@ -19,6 +21,12 @@ void Utils::setParentWindow(QWidget *w, const QString &parent_window)
         w->setAttribute(Qt::WA_NativeWindow, true);
         setParentWindow(w->windowHandle(), parent_window);
     }
+    if (parent_window.startsWith((QLatin1String("wayland:")))) {
+        if (!w->window()->windowHandle()) {
+            w->window()->winId(); // create QWindow
+        }
+        setParentWindow(w->window()->windowHandle(), parent_window);
+    }
 }
 
 void Utils::setParentWindow(QWindow *w, const QString &parent_window)
@@ -26,6 +34,9 @@ void Utils::setParentWindow(QWindow *w, const QString &parent_window)
     if (parent_window.startsWith(QLatin1String("x11:"))) {
         KWindowSystem::setMainWindow(w, parent_window.midRef(4).toULongLong(nullptr, 16));
     }
+    if (parent_window.startsWith((QLatin1String("wayland:")))) {
+        WaylandIntegration::setParentWindow(w, parent_window.mid(strlen("wayland:")));
+    }
 }
 
 QString Utils::applicationName(const QString &appName)

src/waylandintegration.cpp

@@ -31,6 +31,8 @@
 #include <KWayland/Client/plasmawindowmanagement.h>
 #include <KWayland/Client/plasmawindowmodel.h>
 #include <KWayland/Client/registry.h>
+#include <KWayland/Client/surface.h>
+#include <KWayland/Client/xdgforeign.h>
 
 // system
 #include <fcntl.h>
@@ -129,6 +131,11 @@ QVariant WaylandIntegration::streams()
     return globalWaylandIntegration->streams();
 }
 
+void WaylandIntegration::setParentWindow(QWindow *window, const QString &parentWindow)
+{
+    globalWaylandIntegration->setParentWindow(window, parentWindow);
+}
+
 // Thank you kscreen
 void WaylandIntegration::WaylandOutput::setOutputType(const QString &type)
 {
@@ -393,6 +400,28 @@ QVariant WaylandIntegration::WaylandIntegrationPrivate::streams()
     return QVariant::fromValue<WaylandIntegrationPrivate::Streams>(m_streams);
 }
 
+void WaylandIntegration::WaylandIntegrationPrivate::setParentWindow(QWindow *window, const QString &parentHandle)
+{
+    if (!m_xdgImporter) {
+        return;
+    }
+
+    auto importedParent = m_xdgImporter->importTopLevel(parentHandle, window);
+    if (window->isVisible()) {
+        importedParent->setParentOf(KWayland::Client::Surface::fromWindow(window));
+    } else {
+        connect(
+            window,
+            &QWindow::visibleChanged,
+            this,
+            [importedParent, window, this] {
+                importedParent->setParentOf(KWayland::Client::Surface::fromWindow(window));
+                QObject::disconnect(this);
+            },
+            Qt::QueuedConnection);
+    }
+}
+
 void WaylandIntegration::WaylandIntegrationPrivate::authenticate()
 {
     if (!m_waylandAuthenticationRequested) {
@@ -459,7 +488,9 @@ void WaylandIntegration::WaylandIntegrationPrivate::initWayland()
         m_windowManagement = m_registry->createPlasmaWindowManagement(name, version, this);
         Q_EMIT waylandIntegration()->plasmaWindowManagementInitialized();
     });
-
+    connect(m_registry, &KWayland::Client::Registry::importerUnstableV2Announced, this, [this](quint32 name, quint32 version) {
+        m_xdgImporter = m_registry->createXdgImporter(name, std::min(version, quint32(1)), this);
+    });
     connect(m_registry, &KWayland::Client::Registry::interfacesAnnounced, this, [this] {
         m_registryInitialized = true;
         qCDebug(XdgDesktopPortalKdeWaylandIntegration) << "Registry initialized";

src/waylandintegration.h

@@ -26,6 +26,8 @@ class ScreencastingSource;
 }
 }
 
+class QWindow;
+
 namespace WaylandIntegration
 {
 class WaylandOutput
@@ -125,6 +127,8 @@ void requestKeyboardKeycode(int keycode, bool state);
 QMap<quint32, WaylandOutput> screens();
 QVariant streams();
 
+void setParentWindow(QWindow *window, const QString &parentWindow);
+
 void init();
 
 KWayland::Client::PlasmaWindowManagement *plasmaWindowManagement();

src/waylandintegration_p.h

@@ -30,9 +30,12 @@ class PlasmaWindowManagement;
 class FakeInput;
 class RemoteBuffer;
 class Output;
+class XdgImporter;
 }
 }
 
+class QWindow;
+
 namespace WaylandIntegration
 {
 class WaylandIntegrationPrivate : public WaylandIntegration::WaylandIntegration
@@ -51,6 +54,7 @@ private:
 
     KWayland::Client::Registry *m_registry = nullptr;
     KWayland::Client::PlasmaWindowManagement *m_windowManagement = nullptr;
+    KWayland::Client::XdgImporter *m_xdgImporter = nullptr;
 
 public:
     struct Stream {
@@ -85,6 +89,8 @@ public:
     QMap<quint32, WaylandOutput> screens();
     QVariant streams();
 
+    void setParentWindow(QWindow *window, const QString &parentHandle);
+
 protected Q_SLOTS:
     void addOutput(quint32 name, quint32 version);
     void removeOutput(quint32 name);