windows: Fall back to D3D9 when 11 fails

It is assumed that this happens automatically but that is not always the
case. Do not become stuck with a non-functional D3D11-backed EGL environment.
Instead, try again as if QT_ANGLE_PLATFORM=d3d9 was requested.

Task-number: QTBUG-52056
Change-Id: I12ac6ca5f1d06f9504d05120d8e1053e97edfab3
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 45 insertions, 24 deletions

diff --git a/src/plugins/platforms/windows/qwindowseglcontext.cpp b/src/plugins/platforms/windows/qwindowseglcontext.cpp
index 787a072a7a..9ae1ca8acb 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowseglcontext.cpp
@@ -347,26 +347,9 @@ QWindowsEGLStaticContext::QWindowsEGLStaticContext(EGLDisplay display)
 {
 }
 
-QWindowsEGLStaticContext *QWindowsEGLStaticContext::create(QWindowsOpenGLTester::Renderers preferredType)
+bool QWindowsEGLStaticContext::initializeAngle(QWindowsOpenGLTester::Renderers preferredType, HDC dc,
+                                               EGLDisplay *display, EGLint *major, EGLint *minor)
 {
-    const HDC dc = QWindowsContext::instance()->displayContext();
-    if (!dc){
-        qWarning("%s: No Display", __FUNCTION__);
-        return 0;
-    }
-
-    if (!libEGL.init()) {
-        qWarning("%s: Failed to load and resolve libEGL functions", __FUNCTION__);
-        return 0;
-    }
-    if (!libGLESv2.init()) {
-        qWarning("%s: Failed to load and resolve libGLESv2 functions", __FUNCTION__);
-        return 0;
-    }
-
-    EGLDisplay display = EGL_NO_DISPLAY;
-    EGLint major = 0;
-    EGLint minor = 0;
 #ifdef EGL_ANGLE_platform_angle
     if (libEGL.eglGetPlatformDisplayEXT
         && (preferredType & QWindowsOpenGLTester::AngleBackendMask)) {
@@ -384,16 +367,52 @@ QWindowsEGLStaticContext *QWindowsEGLStaticContext::create(QWindowsOpenGLTester:
         else if (preferredType & QWindowsOpenGLTester::AngleRendererD3d11Warp)
             attributes = anglePlatformAttributes[2];
         if (attributes) {
-            display = libEGL.eglGetPlatformDisplayEXT(EGL_PLATFORM_ANGLE_ANGLE, dc, attributes);
-            if (!libEGL.eglInitialize(display, &major, &minor)) {
-                display = EGL_NO_DISPLAY;
-                major = minor = 0;
+            *display = libEGL.eglGetPlatformDisplayEXT(EGL_PLATFORM_ANGLE_ANGLE, dc, attributes);
+            if (!libEGL.eglInitialize(*display, major, minor)) {
+                libEGL.eglTerminate(*display);
+                *display = EGL_NO_DISPLAY;
+                *major = *minor = 0;
+                return false;
             }
         }
     }
 #else // EGL_ANGLE_platform_angle
-    Q_UNUSED(preferredType)
+    Q_UNUSED(preferredType);
+    Q_UNUSED(dc);
+    Q_UNUSED(display);
+    Q_UNUSED(major);
+    Q_UNUSED(minor);
 #endif
+    return true;
+}
+
+QWindowsEGLStaticContext *QWindowsEGLStaticContext::create(QWindowsOpenGLTester::Renderers preferredType)
+{
+    const HDC dc = QWindowsContext::instance()->displayContext();
+    if (!dc){
+        qWarning("%s: No Display", __FUNCTION__);
+        return 0;
+    }
+
+    if (!libEGL.init()) {
+        qWarning("%s: Failed to load and resolve libEGL functions", __FUNCTION__);
+        return 0;
+    }
+    if (!libGLESv2.init()) {
+        qWarning("%s: Failed to load and resolve libGLESv2 functions", __FUNCTION__);
+        return 0;
+    }
+
+    EGLDisplay display = EGL_NO_DISPLAY;
+    EGLint major = 0;
+    EGLint minor = 0;
+
+    if (!initializeAngle(preferredType, dc, &display, &major, &minor)
+        && (preferredType & QWindowsOpenGLTester::AngleRendererD3d11)) {
+        preferredType &= ~QWindowsOpenGLTester::AngleRendererD3d11;
+        initializeAngle(preferredType, dc, &display, &major, &minor);
+    }
+
     if (display == EGL_NO_DISPLAY)
         display = libEGL.eglGetDisplay(dc);
     if (!display) {
diff --git a/src/plugins/platforms/windows/qwindowseglcontext.h b/src/plugins/platforms/windows/qwindowseglcontext.h
index 6945939941..1a6058c921 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.h
+++ b/src/plugins/platforms/windows/qwindowseglcontext.h
@@ -271,6 +271,8 @@ public:
 
 private:
     explicit QWindowsEGLStaticContext(EGLDisplay display);
+    static bool initializeAngle(QWindowsOpenGLTester::Renderers preferredType, HDC dc,
+                                EGLDisplay *display, EGLint *major, EGLint *minor);
 
     const EGLDisplay m_display;
 };