From 1c5e709e76a0c8e8ac373c75d823b235f9d1ca78 Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.agocs@qt.io>
Date: Wed, 22 Apr 2020 17:50:44 +0200
Subject: [PATCH] WIP: Limited workaround for device loss

Change-Id: Ia7f7a58ab91eb34cc2cb6283673158e211cadf78
---
 .../platforms/windows/qwindowseglcontext.cpp  | 40 ++++++++++++++++---
 .../platforms/windows/qwindowseglcontext.h    |  3 ++
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowseglcontext.cpp b/src/plugins/platforms/windows/qwindowseglcontext.cpp
index 4ae087dfaa..a6c83b2116 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowseglcontext.cpp
@@ -461,6 +461,37 @@ QWindowsEGLContext::~QWindowsEGLContext()
     }
 }
 
+void QWindowsEGLContext::handleContextLost(QWindowsWindow *window)
+{
+    // Newer ANGLE requires destroying all existing contexts associated with the
+    // EGLDisplay before a subsequent eglCreateContext() is allowed to succeed.
+    QWindowsEGLStaticContext::libEGL.eglDestroyContext(m_eglDisplay, m_eglContext);
+    m_eglContext = EGL_NO_CONTEXT;
+
+    window->invalidateSurface();
+
+
+
+    // ### NB! The following is technically incorrect and is almost certainly guaranteed
+    // to break if more than one QOpenGLContext or window are involved. It does work in a
+    // single QQuickWindow type of applications but is not suitable otherwise. It is also
+    // insufficient for QQuickWidget and friends.
+    //
+    // Instead, the QWindowsEGLStaticContext would need to implement the proper
+    // infrastructure for tracking all associated resources (in a thread safe manner!),
+    // and having a central point of reinitializing which would then invalidate all
+    // associated handles etc. etc.
+
+
+
+    // In addition the EGLDisplay needs to be terminated and reinitialized. (why? is this
+    // a bug in ANGLE?)
+    EGLint major = 0;
+    EGLint minor = 0;
+    QWindowsEGLStaticContext::libEGL.eglTerminate(m_eglDisplay);
+    QWindowsEGLStaticContext::libEGL.eglInitialize(m_eglDisplay, &major, &minor);
+}
+
 bool QWindowsEGLContext::makeCurrent(QPlatformSurface *surface)
 {
     Q_ASSERT(surface->surface()->supportsOpenGL());
@@ -473,8 +504,8 @@ bool QWindowsEGLContext::makeCurrent(QPlatformSurface *surface)
     auto eglSurface = static_cast<EGLSurface>(window->surface(m_eglConfig, &err));
     if (eglSurface == EGL_NO_SURFACE) {
         if (err == EGL_CONTEXT_LOST) {
-            m_eglContext = EGL_NO_CONTEXT;
             qCDebug(lcQpaGl) << "Got EGL context lost in createWindowSurface() for context" << this;
+            handleContextLost(window);
         } else if (err == EGL_BAD_ACCESS) {
             // With ANGLE this means no (D3D) device and can happen when disabling/changing graphics adapters.
             qCDebug(lcQpaGl) << "Bad access (missing device?) in createWindowSurface() for context" << this;
@@ -505,10 +536,9 @@ bool QWindowsEGLContext::makeCurrent(QPlatformSurface *surface)
         // 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();
+            handleContextLost(window);
         } else {
             qWarning("%s: Failed to make surface current. eglError: %x, this: %p", __FUNCTION__, err, this);
         }
@@ -534,8 +564,8 @@ void QWindowsEGLContext::swapBuffers(QPlatformSurface *surface)
     auto eglSurface = static_cast<EGLSurface>(window->surface(m_eglConfig, &err));
     if (eglSurface == EGL_NO_SURFACE) {
         if (err == EGL_CONTEXT_LOST) {
-            m_eglContext = EGL_NO_CONTEXT;
             qCDebug(lcQpaGl) << "Got EGL context lost in createWindowSurface() for context" << this;
+            handleContextLost(window);
         }
         return;
     }
@@ -544,8 +574,8 @@ void QWindowsEGLContext::swapBuffers(QPlatformSurface *surface)
     if (!ok) {
         err =  QWindowsEGLStaticContext::libEGL.eglGetError();
         if (err == EGL_CONTEXT_LOST) {
-            m_eglContext = EGL_NO_CONTEXT;
             qCDebug(lcQpaGl) << "Got EGL context lost in eglSwapBuffers()";
+            handleContextLost(window);
         } else {
             qWarning("%s: Failed to swap buffers. eglError: %d, this: %p", __FUNCTION__, err, this);
         }
diff --git a/src/plugins/platforms/windows/qwindowseglcontext.h b/src/plugins/platforms/windows/qwindowseglcontext.h
index d96e266159..b556d5bd2a 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.h
+++ b/src/plugins/platforms/windows/qwindowseglcontext.h
@@ -46,6 +46,8 @@
 
 QT_BEGIN_NAMESPACE
 
+class QWindowsWindow;
+
 struct QWindowsLibEGL
 {
     bool init();
@@ -160,6 +162,7 @@ public:
 
 private:
     EGLConfig chooseConfig(const QSurfaceFormat &format);
+    void handleContextLost(QWindowsWindow *window);
 
     QWindowsEGLStaticContext *m_staticContext;
     EGLContext m_eglContext;
-- 
2.23.0.windows.1