Revert "gl: simplify tls"

This reverts commit e7413c2.
rendering thread can have multiple contexts, OpenGLVideo in each context
should not share the same tls one.

src/opengl/OpenGLVideo.cpp

@@ -117,21 +117,24 @@ void OpenGLVideoPrivate::updateGeometry(VideoShader* shader, const QRectF &t, co
         tex_target = shader->textureTarget();
         update_geo = true;
     }
-    // unlike thread_local, QThreadStorage<T*> will delete ptr at thread exit, so we store quintptr
-    static QThreadStorage<quintptr> tls_gr; // TODO: only update VAO, not the whole GeometryRenderer
-    if (!tls_gr.hasLocalData()) {
-        qDebug("creating GeometryRenderer...");
-        GeometryRenderer* tls_gr_ptr = new GeometryRenderer(); // local var is captured by lambda
-        tls_gr.setLocalData(quintptr(tls_gr_ptr));
+    bool update_gr = false;
+    static QThreadStorage<bool> new_thread;
+    if (!new_thread.hasLocalData())
+        new_thread.setLocalData(true);
+
+    update_gr = new_thread.localData();
+    if (!gr || update_gr) { // TODO: only update VAO, not the whole GeometryRenderer
         update_geo = true;
+        new_thread.setLocalData(false);
+        GeometryRenderer *r = new GeometryRenderer(); // local var is captured by lambda 
+        gr = r;
 #if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0) && defined(Q_COMPILER_LAMBDA)
-        QObject::connect(QOpenGLContext::currentContext(), &QOpenGLContext::aboutToBeDestroyed, [tls_gr_ptr]{
-            qDebug("destroy GeometryRenderer %p", tls_gr_ptr);
-            delete tls_gr_ptr;
+        QObject::connect(QOpenGLContext::currentContext(), &QOpenGLContext::aboutToBeDestroyed, [r]{
+            qDebug("destroy GeometryRenderer %p", r);
+            delete r;
         });
 #endif
     }
-    gr = reinterpret_cast<GeometryRenderer*>(tls_gr.localData());
     // (-1, -1, 2, 2) must flip y
     QRectF target_rect = norm_viewport ? QRectF(-1, 1, 2, -2) : rect;
     if (target.isValid()) {