Expose context loss

On platforms like Windows (and presumably on mobile devices too)
the loss of the context (e.g. the underlying D3D device in case of
ANGLE) is an event that can happen randomly and needs sufficient
handling.

Enhance QOpenGLContext::isValid() with the purpose of indicating
context loss.

Currently only the Windows EGL backend (ANGLE) has support for it.
Other platforms may be added later.

Task-number: QTBUG-43263
Change-Id: I8177694c1ee7cebbd5d330e34757fd94c563e6d6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

3 files changed, 20 insertions, 1 deletions

diff --git a/src/plugins/platforms/windows/qwindowseglcontext.cpp b/src/plugins/platforms/windows/qwindowseglcontext.cpp
index c0d0c1f77c..0872741e47 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowseglcontext.cpp
@@ -592,7 +592,17 @@ bool QWindowsEGLContext::makeCurrent(QPlatformSurface *surface)
             QWindowsEGLStaticContext::libEGL.eglSwapInterval(m_staticContext->display(), m_swapInterval);
         }
     } else {
-        qWarning("QWindowsEGLContext::makeCurrent: eglError: %x, this: %p \n", QWindowsEGLStaticContext::libEGL.eglGetError(), this);
+        int err = QWindowsEGLStaticContext::libEGL.eglGetError();
+        // EGL_CONTEXT_LOST (loss of the D3D device) is not necessarily fatal.
+        // Qt Quick is able to recover for example.
+        if (err == EGL_CONTEXT_LOST) {
+            m_eglContext = EGL_NO_CONTEXT;
+            qCDebug(lcQpaGl) << "Got EGL context lost in makeCurrent() for context" << this;
+            // Drop the surface. Will recreate on the next makeCurrent.
+            window->invalidateSurface();
+        } else {
+            qWarning("QWindowsEGLContext::makeCurrent: eglError: %x, this: %p \n", err, this);
+        }
     }
 
     return ok;
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 5d94ec3c38..5dfc48df99 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2294,6 +2294,14 @@ void *QWindowsWindow::surface(void *nativeConfig)
 #endif
 }
 
+void QWindowsWindow::invalidateSurface()
+{
+    if (m_surface) {
+        m_data.staticOpenGLContext->destroyWindowSurface(m_surface);
+        m_surface = 0;
+    }
+}
+
 void QWindowsWindow::setTouchWindowTouchTypeStatic(QWindow *window, QWindowsWindowFunctions::TouchWindowTouchTypes touchTypes)
 {
     if (!window->handle())
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index 66102511e0..3e2f488f46 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -254,6 +254,7 @@ public:
     void setWindowIcon(const QIcon &icon);
 
     void *surface(void *nativeConfig);
+    void invalidateSurface() Q_DECL_OVERRIDE;
 
 #ifndef Q_OS_WINCE
     void setAlertState(bool enabled);