Change from QOpenGLWidget to QWindow

While QOpenGLWidget sounds like a good idea, it has issues which are
harder to debug due to how Qt manages the context behind the scenes. We
could probably work around any of these issues over time, but its
probably easier to do it ourselves with a QWindow directly.

Plus using QWindow + createWindowContainer is the easiest to use
configuration for Qt + Vulkan so this is probably much better in the
long run.

src/citra_qt/bootmanager.h

@@ -7,8 +7,9 @@
 #include <atomic>
 #include <condition_variable>
 #include <mutex>
-#include <QOpenGLWidget>
 #include <QThread>
+#include <QWidget>
+#include <QWindow>
 #include "common/thread.h"
 #include "core/core.h"
 #include "core/frontend/emu_window.h"
@@ -117,7 +118,25 @@ signals:
     void ErrorThrown(Core::System::ResultStatus, std::string);
 };
 
-class GRenderWindow : public QOpenGLWidget, public Frontend::EmuWindow {
+class OpenGLWindow : public QWindow {
+    Q_OBJECT
+public:
+    explicit OpenGLWindow(QWindow* parent, QOpenGLContext* shared_context);
+
+    ~OpenGLWindow();
+
+    void Present();
+
+protected:
+    bool event(QEvent* event) override;
+
+    void exposeEvent(QExposeEvent* event) override;
+
+private:
+    QOpenGLContext* context;
+};
+
+class GRenderWindow : public QWidget, public Frontend::EmuWindow {
     Q_OBJECT
 
 public:
@@ -130,9 +149,6 @@ public:
     void PollEvents() override;
     std::unique_ptr<Frontend::GraphicsContext> CreateSharedContext() const override;
 
-    void initializeGL() override;
-    void paintGL() override;
-
     void BackupGeometry();
     void RestoreGeometry();
     void restoreGeometry(const QByteArray& geometry); // overridden
@@ -181,6 +197,14 @@ private:
 
     QByteArray geometry;
 
+    /// Native window handle that backs this presentation widget
+    QWindow* child_window = nullptr;
+
+    /// In order to embed the window into GRenderWindow, you need to use createWindowContainer to
+    /// put the child_window into a widget then add it to the layout. This child_widget can be
+    /// parented to GRenderWindow and use Qt's lifetime system
+    QWidget* child_widget = nullptr;
+
     EmuThread* emu_thread;
 
     /// Temporary storage of the screenshot taken