Introduce path for surviving compositor restarts

This patch introduces an optional mechanism for clients to survive a
crash and reconnect seemingly seamlessly.

In the event of a disconnect from the compositor socket we simply try to
reconnect again and replay any data needed so that we maintain a
consistent state to where we left off.

From an application point-of-view any open popups will be dismissed and
we we potentially get a new framecallback, but it will be almost
entirely transparent. Users of custom QWaylandClientExtensions will be
notified via the activeChanged signal and rebuild as though the
compositor had withdrawn and re-announced the global.

OpenGL contexts will be marked as invalid, and handled the same way as a
GPU reset. On the next frame RHI will notice these are invalid and
recreate them, only now against a new wl_display and new EGLDisplay.

Users of low level EGL/native objects might be affected, but the
alternative at this point is being closed anyway. The entire codepath is
only activated via an environment variable.

Change-Id: I6c4acc885540e14cead7640794df86dd974fef4f
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

4 files changed, 17 insertions, 0 deletions

diff --git a/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow.cpp b/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow.cpp
index 8221d5d9..ca7d58f3 100644
--- a/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow.cpp
+++ b/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow.cpp
@@ -140,6 +140,12 @@ void QWaylandEglWindow::invalidateSurface()
     m_contentFBO = nullptr;
 }
 
+void QWaylandEglWindow::reinit()
+{
+    QWaylandWindow::reinit();
+    m_clientBufferIntegration = static_cast<QWaylandEglClientBufferIntegration *>(mDisplay->clientBufferIntegration());
+}
+
 EGLSurface QWaylandEglWindow::eglSurface() const
 {
     return m_eglSurface;
diff --git a/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow_p.h b/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow_p.h
index 5b9aa987..cfcdd577 100644
--- a/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow_p.h
+++ b/src/hardwareintegration/client/wayland-egl/qwaylandeglwindow_p.h
@@ -50,6 +50,7 @@ public:
     void bindContentFBO();
 
     void invalidateSurface() override;
+    void reinit() override;
 
 private:
     QWaylandEglClientBufferIntegration *m_clientBufferIntegration = nullptr;
diff --git a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp
index 0b64db5c..050b3eba 100644
--- a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp
+++ b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp
@@ -195,6 +195,10 @@ QWaylandGLContext::QWaylandGLContext(EGLDisplay eglDisplay, QWaylandDisplay *dis
                                      const QSurfaceFormat &fmt, QPlatformOpenGLContext *share)
     : QEGLPlatformContext(fmt, share, eglDisplay), m_display(display)
 {
+    m_reconnectionWatcher = QObject::connect(m_display, &QWaylandDisplay::reconnected, [this]() {
+        invalidateContext();
+    });
+
     switch (format().renderableType()) {
     case QSurfaceFormat::OpenVG:
         m_api = EGL_OPENVG_API;
@@ -260,6 +264,7 @@ void QWaylandGLContext::destroyTemporaryOffscreenSurface(EGLSurface eglSurface)
 
 QWaylandGLContext::~QWaylandGLContext()
 {
+    QObject::disconnect(m_reconnectionWatcher);
     delete m_blitter;
     m_blitter = nullptr;
     if (m_decorationsContext != EGL_NO_CONTEXT)
@@ -280,6 +285,10 @@ void QWaylandGLContext::endFrame()
 
 bool QWaylandGLContext::makeCurrent(QPlatformSurface *surface)
 {
+    if (!isValid()) {
+        return false;
+    }
+
     // in QWaylandGLContext() we called eglBindAPI with the correct value. However,
     // eglBindAPI's documentation says:
     // "eglBindAPI defines the current rendering API for EGL in the thread it is called from"
diff --git a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext_p.h b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext_p.h
index 00ef99b1..b985c667 100644
--- a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext_p.h
+++ b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext_p.h
@@ -62,6 +62,7 @@ private:
     wl_surface *m_wlSurface = nullptr;
     wl_egl_window *m_eglWindow = nullptr;
     QWaylandEglWindow *m_currentWindow = nullptr;
+    QMetaObject::Connection m_reconnectionWatcher;
 };
 
 }