xdg-shell v6: Make sure popup parent is topmost popup when grabbing

Avoids protocol errors on Weston, gnome-shell and wlroots-based
compositors.

[ChangeLog][QPA Plugin] Fixed a protocol error that sometimes happened
when showing popups such as nested menus on xdg-shell unstable v6.

Task-number: QTBUG-67988
Change-Id: I037aec94fba3d177dd0392e5a216a604bc65ac4f
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

2 files changed, 36 insertions, 5 deletions

diff --git a/src/client/qwaylandxdgshellv6.cpp b/src/client/qwaylandxdgshellv6.cpp
index a166a3bc9..5bcd3b254 100644
--- a/src/client/qwaylandxdgshellv6.cpp
+++ b/src/client/qwaylandxdgshellv6.cpp
@@ -93,6 +93,7 @@ QWaylandXdgSurfaceV6::Popup::Popup(QWaylandXdgSurfaceV6 *xdgSurface, QWaylandXdg
                                    QtWayland::zxdg_positioner_v6 *positioner)
     : zxdg_popup_v6(xdgSurface->get_popup(parent->object(), positioner->object()))
     , m_xdgSurface(xdgSurface)
+    , m_parent(parent)
 {
 }
 
@@ -100,6 +101,12 @@ QWaylandXdgSurfaceV6::Popup::~Popup()
 {
     if (isInitialized())
         destroy();
+
+    if (m_grabbing) {
+        auto *shell = m_xdgSurface->m_shell;
+        Q_ASSERT(shell->m_topmostPopup == this);
+        shell->m_topmostPopup = m_parent->m_popup;
+    }
 }
 
 void QWaylandXdgSurfaceV6::Popup::applyConfigure()
@@ -107,6 +114,13 @@ void QWaylandXdgSurfaceV6::Popup::applyConfigure()
 
 }
 
+void QWaylandXdgSurfaceV6::Popup::grab(QWaylandInputDevice *seat, uint serial)
+{
+    m_xdgSurface->m_shell->m_topmostPopup = this;
+    zxdg_popup_v6::grab(seat->wl_seat(), serial);
+    m_grabbing = true;
+}
+
 void QWaylandXdgSurfaceV6::Popup::zxdg_popup_v6_popup_done()
 {
     m_xdgSurface->m_window->window()->close();
@@ -124,8 +138,10 @@ QWaylandXdgSurfaceV6::~QWaylandXdgSurfaceV6()
 {
     if (m_toplevel)
         zxdg_toplevel_v6_destroy(m_toplevel->object());
-    if (m_popup)
-        zxdg_popup_v6_destroy(m_popup->object());
+    if (m_popup) {
+        delete m_popup;
+        m_popup = nullptr;
+    }
     destroy();
 }
 
@@ -198,6 +214,14 @@ void QWaylandXdgSurfaceV6::setPopup(QWaylandWindow *parent, QWaylandInputDevice
     Q_ASSERT(!m_toplevel && !m_popup);
 
     auto parentXdgSurface = static_cast<QWaylandXdgSurfaceV6 *>(parent->shellSurface());
+
+    auto *top = m_shell->m_topmostPopup;
+    if (grab && top && top->m_xdgSurface != parentXdgSurface) {
+        qCWarning(lcQpaWayland) << "setPopup called for a surface that was not the topmost popup, positions might be off.";
+        parentXdgSurface = top->m_xdgSurface;
+        parent = top->m_xdgSurface->m_window;
+    }
+
     auto positioner = new QtWayland::zxdg_positioner_v6(m_shell->create_positioner());
     // set_popup expects a position relative to the parent
     QPoint transientPos = m_window->geometry().topLeft(); // this is absolute
@@ -213,9 +237,8 @@ void QWaylandXdgSurfaceV6::setPopup(QWaylandWindow *parent, QWaylandInputDevice
     m_popup = new Popup(this, parentXdgSurface, positioner);
     positioner->destroy();
     delete positioner;
-    if (grab) {
-        m_popup->grab(device->wl_seat(), serial);
-    }
+    if (grab)
+        m_popup->grab(device, serial);
 }
 
 void QWaylandXdgSurfaceV6::zxdg_surface_v6_configure(uint32_t serial)
diff --git a/src/client/qwaylandxdgshellv6_p.h b/src/client/qwaylandxdgshellv6_p.h
index b72d3d18a..e6434c02f 100644
--- a/src/client/qwaylandxdgshellv6_p.h
+++ b/src/client/qwaylandxdgshellv6_p.h
@@ -115,9 +115,12 @@ private:
         ~Popup() override;
 
         void applyConfigure();
+        void grab(QWaylandInputDevice *seat, uint serial);
         void zxdg_popup_v6_popup_done() override;
 
         QWaylandXdgSurfaceV6 *m_xdgSurface = nullptr;
+        QWaylandXdgSurfaceV6 *m_parent = nullptr;
+        bool m_grabbing = false;
     };
 
     void setToplevel();
@@ -129,6 +132,8 @@ private:
     Popup *m_popup = nullptr;
     bool m_configured = false;
     QRegion m_exposeRegion;
+
+    friend class QWaylandXdgShellV6;
 };
 
 class Q_WAYLAND_CLIENT_EXPORT QWaylandXdgShellV6 : public QtWayland::zxdg_shell_v6
@@ -142,6 +147,9 @@ public:
 
 private:
     void zxdg_shell_v6_ping(uint32_t serial) override;
+    QWaylandXdgSurfaceV6::Popup *m_topmostPopup = nullptr;
+
+    friend class QWaylandXdgSurfaceV6;
 };
 
 QT_END_NAMESPACE