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 <[email protected]>
leapmotion · Jan 22, 2015 · 2bc038a · 2bc038a
1 parent a2b358e
commit 2bc038a
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Showing 4 changed files with 31 additions and 3 deletions.
diff --git a/src/gui/kernel/qopenglcontext.cpp b/src/gui/kernel/qopenglcontext.cpp
@@ -590,10 +590,10 @@ QVariant QOpenGLContext::nativeHandle() const
 */
 bool QOpenGLContext::create()
 {
-    if (isValid())
+    Q_D(QOpenGLContext);
+    if (d->platformGLContext)
         destroy();
 
-    Q_D(QOpenGLContext);
     d->platformGLContext = QGuiApplicationPrivate::platformIntegration()->createPlatformOpenGLContext(this);
     if (!d->platformGLContext)
         return false;
@@ -676,6 +676,15 @@ QOpenGLContext::~QOpenGLContext()
 /*!
     Returns if this context is valid, i.e. has been successfully created.
 
+    On some platforms the return value of \c false for a context that was
+    successfully created previously indicates that the OpenGL context was lost.
+
+    The typical way to handle context loss scenarios in applications is to
+    check via this function whenever makeCurrent() fails and returns \c false.
+    If this function then returns \c false, recreate the underlying native
+    OpenGL context by calling create(), call makeCurrent() again and then
+    reinitialize all OpenGL resources.
+
     \sa create()
 */
 bool QOpenGLContext::isValid() const

diff --git 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
@@ -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
@@ -254,6 +254,7 @@ class QWindowsWindow : public QPlatformWindow
     void setWindowIcon(const QIcon &icon);
 
     void *surface(void *nativeConfig);
+    void invalidateSurface() Q_DECL_OVERRIDE;
 
 #ifndef Q_OS_WINCE
     void setAlertState(bool enabled);