Client: Don't allow decorations for frameless windows

This only fixes it for when Qt::FramelessWindowHint is set appropriately before
the window is shown.

[ChangeLog][QPA plugin] Windows with Qt::FramelessWindowHint no longer
create zxdg_toplevel_decoration_v1, as that allowed compositors to force
server-side decorations.

Fixes: QTBUG-80702
Change-Id: I47a582a59f6682a57128c0c9d4e4b9a6181925a4
Reviewed-by: Pier Luigi Fiorini <pierluigi.fiorini@liri.io>

2 files changed, 22 insertions, 3 deletions

diff --git a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
index a8e662679..56d77ec4f 100644
--- a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
+++ b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
@@ -56,10 +56,11 @@ QWaylandXdgSurface::Toplevel::Toplevel(QWaylandXdgSurface *xdgSurface)
     : QtWayland::xdg_toplevel(xdgSurface->get_toplevel())
     , m_xdgSurface(xdgSurface)
 {
-    if (auto *decorationManager = m_xdgSurface->m_shell->decorationManager())
-        m_decoration = decorationManager->createToplevelDecoration(object());
-
     QWindow *window = xdgSurface->window()->window();
+    if (auto *decorationManager = m_xdgSurface->m_shell->decorationManager()) {
+        if (!(window->flags() & Qt::FramelessWindowHint))
+            m_decoration = decorationManager->createToplevelDecoration(object());
+    }
     requestWindowStates(window->windowStates());
     requestWindowFlags(window->flags());
 }
diff --git a/tests/auto/client/xdgdecorationv1/tst_xdgdecorationv1.cpp b/tests/auto/client/xdgdecorationv1/tst_xdgdecorationv1.cpp
index 386713cf5..391abd83b 100644
--- a/tests/auto/client/xdgdecorationv1/tst_xdgdecorationv1.cpp
+++ b/tests/auto/client/xdgdecorationv1/tst_xdgdecorationv1.cpp
@@ -153,6 +153,7 @@ private slots:
     void initTestCase();
     void cleanup() { QTRY_VERIFY2(isClean(), qPrintable(dirtyMessage())); }
     void clientSidePreferredByCompositor();
+    void initialFramelessWindowHint();
 };
 
 void tst_xdgdecorationv1::initTestCase()
@@ -182,5 +183,22 @@ void tst_xdgdecorationv1::clientSidePreferredByCompositor()
     QTRY_VERIFY(!window.frameMargins().isNull());
 }
 
+void tst_xdgdecorationv1::initialFramelessWindowHint()
+{
+    QRasterWindow window;
+    window.setFlag(Qt::FramelessWindowHint, true);
+    window.show();
+    QCOMPOSITOR_TRY_COMPARE(get<XdgDecorationManagerV1>()->resourceMap().size(), 1);
+    QCOMPOSITOR_TRY_VERIFY(xdgToplevel());
+    exec([=]{
+        xdgToplevel()->sendCompleteConfigure();
+    });
+    QCOMPOSITOR_TRY_VERIFY(xdgSurface()->m_committedConfigureSerial);
+
+    // The client should not have create a decoration object, because that allows the compositor
+    // to override our decision and add server side decorations to our window.
+    QCOMPOSITOR_TRY_VERIFY(!toplevelDecoration());
+}
+
 QCOMPOSITOR_TEST_MAIN(tst_xdgdecorationv1)
 #include "tst_xdgdecorationv1.moc"