From bdb1c18e411a1660f038e4f0e219d363d38e987a Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Date: Tue, 22 Mar 2016 15:32:36 +0100
Subject: [PATCH] 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>
---
 .../platforms/windows/qwindowseglcontext.cpp  | 71 ++++++++++++-------
 .../platforms/windows/qwindowseglcontext.h    |  2 +
 2 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowseglcontext.cpp b/src/plugins/platforms/windows/qwindowseglcontext.cpp
index 787a072a7a1..9ae1ca8acbe 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowseglcontext.cpp
@@ -347,6 +347,45 @@ QWindowsEGLStaticContext::QWindowsEGLStaticContext(EGLDisplay display)
 {
 }
 
+bool QWindowsEGLStaticContext::initializeAngle(QWindowsOpenGLTester::Renderers preferredType, HDC dc,
+                                               EGLDisplay *display, EGLint *major, EGLint *minor)
+{
+#ifdef EGL_ANGLE_platform_angle
+    if (libEGL.eglGetPlatformDisplayEXT
+        && (preferredType & QWindowsOpenGLTester::AngleBackendMask)) {
+        const EGLint anglePlatformAttributes[][5] = {
+            { EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE, EGL_NONE },
+            { EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_D3D9_ANGLE, EGL_NONE },
+            { EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE,
+              EGL_PLATFORM_ANGLE_DEVICE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_DEVICE_TYPE_WARP_ANGLE, EGL_NONE }
+        };
+        const EGLint *attributes = 0;
+        if (preferredType & QWindowsOpenGLTester::AngleRendererD3d11)
+            attributes = anglePlatformAttributes[0];
+        else if (preferredType & QWindowsOpenGLTester::AngleRendererD3d9)
+            attributes = anglePlatformAttributes[1];
+        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)) {
+                libEGL.eglTerminate(*display);
+                *display = EGL_NO_DISPLAY;
+                *major = *minor = 0;
+                return false;
+            }
+        }
+    }
+#else // EGL_ANGLE_platform_angle
+    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();
@@ -367,33 +406,13 @@ QWindowsEGLStaticContext *QWindowsEGLStaticContext::create(QWindowsOpenGLTester:
     EGLDisplay display = EGL_NO_DISPLAY;
     EGLint major = 0;
     EGLint minor = 0;
-#ifdef EGL_ANGLE_platform_angle
-    if (libEGL.eglGetPlatformDisplayEXT
-        && (preferredType & QWindowsOpenGLTester::AngleBackendMask)) {
-        const EGLint anglePlatformAttributes[][5] = {
-            { EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE, EGL_NONE },
-            { EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_D3D9_ANGLE, EGL_NONE },
-            { EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE,
-              EGL_PLATFORM_ANGLE_DEVICE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_DEVICE_TYPE_WARP_ANGLE, EGL_NONE }
-        };
-        const EGLint *attributes = 0;
-        if (preferredType & QWindowsOpenGLTester::AngleRendererD3d11)
-            attributes = anglePlatformAttributes[0];
-        else if (preferredType & QWindowsOpenGLTester::AngleRendererD3d9)
-            attributes = anglePlatformAttributes[1];
-        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;
-            }
-        }
+
+    if (!initializeAngle(preferredType, dc, &display, &major, &minor)
+        && (preferredType & QWindowsOpenGLTester::AngleRendererD3d11)) {
+        preferredType &= ~QWindowsOpenGLTester::AngleRendererD3d11;
+        initializeAngle(preferredType, dc, &display, &major, &minor);
     }
-#else // EGL_ANGLE_platform_angle
-    Q_UNUSED(preferredType)
-#endif
+
     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 6945939941d..1a6058c9210 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;
 };