Compositor: Warn and clean up when client hardware buffer integrations fail

We've recently seen a number of performance issues on bugreports and on the
mailing list. The problem in many of these cases, is that no client hardware
buffer plugin is used. I.e. it's just due to our fallback to CPU buffers when
the compositor is configured incorrectly or run in a setup where hardware
buffers are not available.

This patch detects when client hardware buffer plugins fail and prints a
warning explaining the issue to the console.

This will make it easier to differentiate between expected and unexpected drops
in performance and will hopefully also guide users in the right direction
to fix their setup (set the right environment variables and perhaps recompile
Qt with a supported OpenGL version).

QtWayland::ClientBufferIntegration now returns a bool indicating success or
failure. The integration is now destroyed immediately if it failed, instead of
leaving it lying around until the compositor shuts down.

There has been some slight changes in the xcomposite plugins as well, turning
some qFatals into qCWarnings and failing more softly (with the warning
mentioned above).

Task-number: QTBUG-78483
Change-Id: I55293dbb3cf72768f3982c075fcf63e79329ada1
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

1 files changed, 23 insertions, 5 deletions

diff --git a/src/compositor/compositor_api/qwaylandcompositor.cpp b/src/compositor/compositor_api/qwaylandcompositor.cpp
index 7c3750207..52a6614bc 100644
--- a/src/compositor/compositor_api/qwaylandcompositor.cpp
+++ b/src/compositor/compositor_api/qwaylandcompositor.cpp
@@ -366,8 +366,6 @@ void QWaylandCompositorPrivate::initializeHardwareIntegration()
     loadClientBufferIntegration();
     loadServerBufferIntegration();
 
-    if (client_buffer_integration)
-        client_buffer_integration->initializeHardware(display);
     if (server_buffer_integration)
         server_buffer_integration->initializeHardware(q);
 #endif
@@ -399,12 +397,32 @@ void QWaylandCompositorPrivate::loadClientBufferIntegration()
     if (!targetKey.isEmpty()) {
         client_buffer_integration.reset(QtWayland::ClientBufferIntegrationFactory::create(targetKey, QStringList()));
         if (client_buffer_integration) {
+            qCDebug(qLcWaylandCompositorHardwareIntegration) << "Loaded client buffer integration:" << targetKey;
             client_buffer_integration->setCompositor(q);
-            if (hw_integration)
-                hw_integration->setClientBufferIntegration(targetKey);
+            if (!client_buffer_integration->initializeHardware(display)) {
+                qCWarning(qLcWaylandCompositorHardwareIntegration)
+                        << "Failed to initialize hardware for client buffer integration:" << targetKey;
+                client_buffer_integration.reset();
+            }
+        } else {
+            qCWarning(qLcWaylandCompositorHardwareIntegration)
+                    << "Failed to load client buffer integration:" << targetKey;
         }
     }
-    //BUG: if there is no client buffer integration, bad things will happen when opengl is used
+
+    if (!client_buffer_integration) {
+        qCWarning(qLcWaylandCompositorHardwareIntegration)
+                << "No client buffer integration was loaded, this means that clients will fall back"
+                << "to use CPU buffers (wl_shm) for transmitting buffers instead of using zero-copy"
+                << "GPU buffer handles. Expect serious performance impact with OpenGL clients due"
+                << "to potentially multiple copies between CPU and GPU memory per buffer.\n"
+                << "See the QtWayland readme for more info about how to build and configure Qt for"
+                << "your device.";
+        return;
+    }
+
+    if (client_buffer_integration && hw_integration)
+        hw_integration->setClientBufferIntegration(targetKey);
 #endif
 }