Fix leak in multi-output compositor examples

When closing windows in e.g. multi-output, you will see warnings
that textures are leaking because the current context is not
shared with the context owning the texture.

The way Qt Wayland Compositor internals are made, they depend
on AA_ShareOpenGLContexts to be set, because buffers are consistently
referenced across window/context boundaries. Change
f1407493d6d25f24a3c71fbcedc00598baa44b56 mentions the requirement
on EGLStreams, but this is also required on multi-output compositors
to avoid leaks (and possibly sometimes crashes on some drivers).

Task-number: QTBUG-87597
Change-Id: Ib0ccc61dee5dbc63704b0af1432fbf69645d39eb
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

2 files changed, 6 insertions, 0 deletions

diff --git a/examples/wayland/multi-screen/doc/src/multi-screen.qdoc b/examples/wayland/multi-screen/doc/src/multi-screen.qdoc
index cd60213b5..5e8e74557 100644
--- a/examples/wayland/multi-screen/doc/src/multi-screen.qdoc
+++ b/examples/wayland/multi-screen/doc/src/multi-screen.qdoc
@@ -42,4 +42,8 @@
  * WaylandQuickItem::setPrimary() is called at appropriate times to set the
  * primary view for the ShellSurface, which is used when the client asks to be
  * maximized or fullscreen.
+ *
+ * \note In order to support multiple Wayland outputs in the same compositor, the
+ * \l Qt::AA_ShareOpenGLContexts attribute must be set before the \l QGuiApplication
+ * object is constructed.
  */
diff --git a/examples/wayland/multi-screen/main.cpp b/examples/wayland/multi-screen/main.cpp
index 304b13c4a..1edb18c34 100644
--- a/examples/wayland/multi-screen/main.cpp
+++ b/examples/wayland/multi-screen/main.cpp
@@ -57,6 +57,8 @@
 
 int main(int argc, char *argv[])
 {
+    // AA_ShareOpenGLContexts is required for compositors with multiple outputs
+    QCoreApplication::setAttribute(Qt::AA_ShareOpenGLContexts, true);
     QGuiApplication app(argc, argv);
 
     QQmlApplicationEngine appEngine(QUrl("qrc:///qml/main.qml"));