1 files changed, 53 insertions, 0 deletions
diff --git a/src/core/browser_main_parts_qt.cpp b/src/core/browser_main_parts_qt.cpp
index 8f39386d4..056d6fda8 100644
--- a/src/core/browser_main_parts_qt.cpp
+++ b/src/core/browser_main_parts_qt.cpp
@@ -59,6 +59,12 @@
 #include <QEventLoop>
 #include <QObject>
 #include <QTimerEvent>
+#include <QtGui/qtgui-config.h>
+
+#if QT_CONFIG(opengl)
+#include "ui/gl/gl_context.h"
+#include <QOpenGLContext>
+#endif
 
 #if defined(OS_MACOSX)
 #include "ui/base/idle/idle.h"
@@ -156,8 +162,55 @@ protected:
     }
 
 private:
+    // Both Qt and Chromium keep track of the current GL context by using
+    // thread-local variables, and naturally they are completely unaware of each
+    // other. As a result, when a QOpenGLContext is made current, the previous
+    // gl::GLContext is not released, and vice-versa. This is fine as long as
+    // each thread uses exclusively either Qt or Chromium GL bindings, which is
+    // usually the case.
+    //
+    // The only exception is when the GL driver is considered thread-unsafe
+    // (QOpenGLContext::supportsThreadedOpenGL() is false), in which case we
+    // have to run all GL operations, including Chromium's GPU service, on the
+    // UI thread. Now the bindings are being mixed and both Qt and Chromium get
+    // quite confused regarding the current state of the surface.
+    //
+    // To get this to work we have to release the current QOpenGLContext before
+    // executing any tasks from Chromium's GPU service and the gl::GLContext
+    // afterwards. Since GPU service just posts tasks to the UI thread task
+    // runner, we'll have to instrument the entire UI thread message pump.
+    class ScopedGLContextChecker
+    {
+#if QT_CONFIG(opengl)
+    public:
+        ScopedGLContextChecker()
+        {
+            if (!m_enabled)
+                return;
+
+            if (QOpenGLContext *context = QOpenGLContext::currentContext())
+                context->doneCurrent();
+        }
+
+        ~ScopedGLContextChecker()
+        {
+            if (!m_enabled)
+                return;
+
+            if (gl::GLContext *context = gl::GLContext::GetCurrent())
+                context->ReleaseCurrent(nullptr);
+        }
+
+    private:
+        bool m_enabled = !QOpenGLContext::supportsThreadedOpenGL();
+#endif // QT_CONFIG(opengl)
+    };
+
+
     void handleScheduledWork()
     {
+        ScopedGLContextChecker glContextChecker;
+
         bool more_work_is_plausible = m_delegate->DoWork();
 
         base::TimeTicks delayed_work_time;