WGL: support reset notifications via GL_ARB_robustness

Handling context losses is unavoidable with ANGLE. Introduce
some level of support for desktop GL too by making it possible
to opt in via a new flag.

Support is added for Windows (WGL, opengl32) only for now.
In case of Windows with ANGLE setting the flag is not necessary,
context losses will be reported regardless.

Change-Id: Ic354c1382e876566538c52a4381f7ff328b7477e
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

2 files changed, 51 insertions, 2 deletions

diff --git a/src/plugins/platforms/windows/qwindowsglcontext.cpp b/src/plugins/platforms/windows/qwindowsglcontext.cpp
index 0e3e6826ec..786a662287 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowsglcontext.cpp
@@ -135,6 +135,10 @@
 #define GL_CONTEXT_FLAG_DEBUG_BIT 0x00000002
 #endif
 
+// Common GL and WGL constants
+#define RESET_NOTIFICATION_STRATEGY_ARB 0x8256
+#define LOSE_CONTEXT_ON_RESET_ARB 0x8252
+
 QT_BEGIN_NAMESPACE
 
 QWindowsOpengl32DLL QOpenGLStaticContext::opengl32;
@@ -747,6 +751,12 @@ static HGLRC createContext(const QOpenGLStaticContext &staticContext,
             break;
         }
     }
+
+    if (format.testOption(QSurfaceFormat::ResetNotification)) {
+        attributes[attribIndex++] = RESET_NOTIFICATION_STRATEGY_ARB;
+        attributes[attribIndex++] = LOSE_CONTEXT_ON_RESET_ARB;
+    }
+
     qCDebug(lcQpaGl) << __FUNCTION__ << "Creating context version"
         << majorVersion << '.' << minorVersion <<  attribIndex / 2 << "attributes";
 
@@ -859,6 +869,10 @@ QWindowsOpenGLContextFormat QWindowsOpenGLContextFormat::current()
         result.options |= QSurfaceFormat::DeprecatedFunctions;
     if (value & GL_CONTEXT_FLAG_DEBUG_BIT)
         result.options |= QSurfaceFormat::DebugContext;
+    value = 0;
+    QOpenGLStaticContext::opengl32.glGetIntegerv(RESET_NOTIFICATION_STRATEGY_ARB, &value);
+    if (value == LOSE_CONTEXT_ON_RESET_ARB)
+        result.options |= QSurfaceFormat::ResetNotification;
     if (result.version < 0x0302)
         return result;
     // v3.2 onwards: Profiles
@@ -1032,7 +1046,9 @@ QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext,
     m_pixelFormat(0),
     m_extensionsUsed(false),
     m_swapInterval(-1),
-    m_ownsContext(true)
+    m_ownsContext(true),
+    m_getGraphicsResetStatus(0),
+    m_lost(false)
 {
     if (!m_staticContext) // Something went very wrong. Stop here, isValid() will return false.
         return;
@@ -1212,6 +1228,28 @@ bool QWindowsGLContext::updateObtainedParams(HDC hdc, int *obtainedSwapInterval)
     if (m_staticContext->wglGetSwapInternalExt && obtainedSwapInterval)
         *obtainedSwapInterval = m_staticContext->wglGetSwapInternalExt();
 
+    bool hasRobustness = false;
+    if (m_obtainedFormat.majorVersion() < 3) {
+        const char *exts = (const char *) QOpenGLStaticContext::opengl32.glGetString(GL_EXTENSIONS);
+        hasRobustness = exts && strstr(exts, "GL_ARB_robustness");
+    } else {
+        typedef const GLubyte * (APIENTRY *glGetStringi_t)(GLenum, GLuint);
+        glGetStringi_t glGetStringi = (glGetStringi_t) QOpenGLStaticContext::opengl32.wglGetProcAddress("glGetStringi");
+        if (glGetStringi) {
+            GLint n = 0;
+            QOpenGLStaticContext::opengl32.glGetIntegerv(GL_NUM_EXTENSIONS, &n);
+            for (GLint i = 0; i < n; ++i) {
+                const char *p = (const char *) glGetStringi(GL_EXTENSIONS, i);
+                if (p && !strcmp(p, "GL_ARB_robustness")) {
+                    hasRobustness = true;
+                    break;
+                }
+            }
+        }
+    }
+    if (hasRobustness)
+        m_getGraphicsResetStatus = (GLenum (APIENTRY *)()) QOpenGLStaticContext::opengl32.wglGetProcAddress("glGetGraphicsResetStatusARB");
+
     QOpenGLStaticContext::opengl32.wglMakeCurrent(prevSurface, prevContext);
     return true;
 }
@@ -1296,7 +1334,16 @@ bool QWindowsGLContext::makeCurrent(QPlatformSurface *surface)
     }
     m_windowContexts.append(newContext);
 
+    m_lost = false;
     bool success = QOpenGLStaticContext::opengl32.wglMakeCurrent(newContext.hdc, newContext.renderingContext);
+    if (!success) {
+        if (m_getGraphicsResetStatus && m_getGraphicsResetStatus()) {
+            m_lost = true;
+            qCDebug(lcQpaGl) << "makeCurrent(): context loss detected" << this;
+            // Drop the surface. Will recreate on the next makeCurrent.
+            window->invalidateSurface();
+        }
+    }
 
     // Set the swap interval
     if (m_staticContext->wglSwapInternalExt) {
diff --git a/src/plugins/platforms/windows/qwindowsglcontext.h b/src/plugins/platforms/windows/qwindowsglcontext.h
index 5f845f245e..27b0b2e191 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.h
+++ b/src/plugins/platforms/windows/qwindowsglcontext.h
@@ -232,7 +232,7 @@ public:
     explicit QWindowsGLContext(QOpenGLStaticContext *staticContext, QOpenGLContext *context);
     ~QWindowsGLContext();
     bool isSharing() const Q_DECL_OVERRIDE { return m_context->shareHandle(); }
-    bool isValid() const Q_DECL_OVERRIDE { return m_renderingContext; }
+    bool isValid() const Q_DECL_OVERRIDE { return m_renderingContext && !m_lost; }
     QSurfaceFormat format() const Q_DECL_OVERRIDE { return m_obtainedFormat; }
 
     void swapBuffers(QPlatformSurface *surface) Q_DECL_OVERRIDE;
@@ -262,6 +262,8 @@ private:
     bool m_extensionsUsed;
     int m_swapInterval;
     bool m_ownsContext;
+    GLenum (APIENTRY * m_getGraphicsResetStatus)();
+    bool m_lost;
 };
 
 QT_END_NAMESPACE