Client: Fail gracefully when wl_display_connect fails

[ChangeLog][QPA plugin] If we're unable to create a connection to the Wayland
display, fail gracefully so other platform integrations can be tried instead.

This also adds QWaylandIntegration::hasFailed() which can later be extended to
report that the platform plugin is unusable for other reasons. I.e. no
compatible shell extensions or similar.

Task-number: QTBUG-59762
Change-Id: I0f1ae73982e2860814235c1a189741d130e1db3e
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

8 files changed, 52 insertions, 9 deletions

diff --git a/src/client/qwaylanddisplay.cpp b/src/client/qwaylanddisplay.cpp
index 942494f93..179c0454e 100644
--- a/src/client/qwaylanddisplay.cpp
+++ b/src/client/qwaylanddisplay.cpp
@@ -142,9 +142,9 @@ QWaylandDisplay::QWaylandDisplay(QWaylandIntegration *waylandIntegration)
     qRegisterMetaType<uint32_t>("uint32_t");
 
     mDisplay = wl_display_connect(nullptr);
-    if (mDisplay == nullptr) {
-        qErrnoWarning(errno, "Failed to create display");
-        ::exit(1);
+    if (!mDisplay) {
+        qErrnoWarning(errno, "Failed to create wl_display");
+        return;
     }
 
     struct ::wl_registry *registry = wl_display_get_registry(mDisplay);
@@ -170,7 +170,8 @@ QWaylandDisplay::~QWaylandDisplay(void)
 #if QT_CONFIG(wayland_datadevice)
     delete mDndSelectionHandler.take();
 #endif
-    wl_display_disconnect(mDisplay);
+    if (mDisplay)
+        wl_display_disconnect(mDisplay);
 }
 
 void QWaylandDisplay::checkError() const
diff --git a/src/client/qwaylandintegration.cpp b/src/client/qwaylandintegration.cpp
index 698abd8fd..267e481ac 100644
--- a/src/client/qwaylandintegration.cpp
+++ b/src/client/qwaylandintegration.cpp
@@ -134,6 +134,10 @@ QWaylandIntegration::QWaylandIntegration()
 {
     initializeInputDeviceIntegration();
     mDisplay.reset(new QWaylandDisplay(this));
+    if (!mDisplay->isInitialized()) {
+        mFailed = true;
+        return;
+    }
 #if QT_CONFIG(clipboard)
     mClipboard.reset(new QWaylandClipboard(mDisplay.data()));
 #endif
diff --git a/src/client/qwaylandintegration_p.h b/src/client/qwaylandintegration_p.h
index 174eca253..17144b8d7 100644
--- a/src/client/qwaylandintegration_p.h
+++ b/src/client/qwaylandintegration_p.h
@@ -73,6 +73,8 @@ public:
     QWaylandIntegration();
     ~QWaylandIntegration();
 
+    bool hasFailed() { return mFailed; }
+
     bool hasCapability(QPlatformIntegration::Capability cap) const override;
     QPlatformWindow *createPlatformWindow(QWindow *window) const override;
 #if QT_CONFIG(opengl)
@@ -144,6 +146,7 @@ private:
 #if QT_CONFIG(accessibility)
     QScopedPointer<QPlatformAccessibility> mAccessibility;
 #endif
+    bool mFailed = false;
     bool mClientBufferIntegrationInitialized;
     bool mServerBufferIntegrationInitialized;
     bool mShellIntegrationInitialized;
diff --git a/src/plugins/platforms/qwayland-brcm-egl/main.cpp b/src/plugins/platforms/qwayland-brcm-egl/main.cpp
index 2640c8ea0..5fa40b8a7 100644
--- a/src/plugins/platforms/qwayland-brcm-egl/main.cpp
+++ b/src/plugins/platforms/qwayland-brcm-egl/main.cpp
@@ -56,7 +56,14 @@ QPlatformIntegration *QWaylandBrcmEglPlatformIntegrationPlugin::create(const QSt
 {
     Q_UNUSED(paramList);
     Q_UNUSED(system);
-    return new QWaylandBrcmEglPlatformIntegration();
+    auto *integration = new QWaylandBrcmEglPlatformIntegration();
+
+    if (integration->hasFailed()) {
+        delete integration;
+        integration = nullptr;
+    }
+
+    return integration;
 }
 
 }
diff --git a/src/plugins/platforms/qwayland-egl/main.cpp b/src/plugins/platforms/qwayland-egl/main.cpp
index ebeeff39f..76b82b3b2 100644
--- a/src/plugins/platforms/qwayland-egl/main.cpp
+++ b/src/plugins/platforms/qwayland-egl/main.cpp
@@ -56,7 +56,14 @@ QPlatformIntegration *QWaylandEglPlatformIntegrationPlugin::create(const QString
 {
     Q_UNUSED(paramList);
     Q_UNUSED(system);
-    return new QWaylandEglPlatformIntegration();
+    auto *integration = new QWaylandEglPlatformIntegration();
+
+    if (integration->hasFailed()) {
+        delete integration;
+        integration = nullptr;
+    }
+
+    return integration;
 }
 
 }
diff --git a/src/plugins/platforms/qwayland-generic/main.cpp b/src/plugins/platforms/qwayland-generic/main.cpp
index 08295c97c..e66a5d45c 100644
--- a/src/plugins/platforms/qwayland-generic/main.cpp
+++ b/src/plugins/platforms/qwayland-generic/main.cpp
@@ -56,7 +56,14 @@ QPlatformIntegration *QWaylandIntegrationPlugin::create(const QString& system, c
 {
     Q_UNUSED(paramList);
     Q_UNUSED(system);
-    return new QWaylandIntegration();
+    auto *integration =  new QWaylandIntegration();
+
+    if (integration->hasFailed()) {
+        delete integration;
+        integration = nullptr;
+    }
+
+    return integration;
 }
 
 }
diff --git a/src/plugins/platforms/qwayland-xcomposite-egl/main.cpp b/src/plugins/platforms/qwayland-xcomposite-egl/main.cpp
index 996f60848..d191bba92 100644
--- a/src/plugins/platforms/qwayland-xcomposite-egl/main.cpp
+++ b/src/plugins/platforms/qwayland-xcomposite-egl/main.cpp
@@ -56,7 +56,14 @@ QPlatformIntegration *QWaylandXCompositeEglPlatformIntegrationPlugin::create(con
 {
     Q_UNUSED(paramList);
     Q_UNUSED(system);
-    return new QWaylandXCompositeEglPlatformIntegration();
+    auto *integration = new QWaylandXCompositeEglPlatformIntegration();
+
+    if (integration->hasFailed()) {
+        delete integration;
+        integration = nullptr;
+    }
+
+    return integration;
 }
 
 }
diff --git a/src/plugins/platforms/qwayland-xcomposite-glx/main.cpp b/src/plugins/platforms/qwayland-xcomposite-glx/main.cpp
index 9f075ebb7..1dfbc0cf4 100644
--- a/src/plugins/platforms/qwayland-xcomposite-glx/main.cpp
+++ b/src/plugins/platforms/qwayland-xcomposite-glx/main.cpp
@@ -58,7 +58,14 @@ QPlatformIntegration *QWaylandXCompositeGlxPlatformIntegrationPlugin::create(con
 {
     Q_UNUSED(paramList);
     Q_UNUSED(system);
-    return new QWaylandXCompositeGlxPlatformIntegration();
+    auto *integration = new QWaylandXCompositeGlxPlatformIntegration();
+
+    if (integration->hasFailed()) {
+        delete integration;
+        integration = nullptr;
+    }
+
+    return integration;
 }
 
 }