diff --git a/src/output/video/OpenGLWindowRenderer.cpp b/src/output/video/OpenGLWindowRenderer.cpp
index b24d92b0..dc71561f 100644
--- a/src/output/video/OpenGLWindowRenderer.cpp
+++ b/src/output/video/OpenGLWindowRenderer.cpp
@@ -68,4 +68,9 @@ void OpenGLWindowRenderer::resizeEvent(QResizeEvent *e)
     QOpenGLWindow::resizeEvent(e); //will call resizeGL(). TODO:will call paintEvent()?
 }
 
+void OpenGLWindowRenderer::showEvent(QShowEvent *)
+{
+    onShowEvent();
+    resizeGL(width(), height());
+}
 } //namespace QtAV
diff --git a/widgets/GLWidgetRenderer2.cpp b/widgets/GLWidgetRenderer2.cpp
index 780b5300..94407c24 100644
--- a/widgets/GLWidgetRenderer2.cpp
+++ b/widgets/GLWidgetRenderer2.cpp
@@ -92,6 +92,6 @@ void GLWidgetRenderer2::resizeEvent(QResizeEvent *e)
 void GLWidgetRenderer2::showEvent(QShowEvent *)
 {
     onShowEvent();
+    resizeGL(width(), height());
 }
-
 } //namespace QtAV
diff --git a/widgets/OpenGLWidgetRenderer.cpp b/widgets/OpenGLWidgetRenderer.cpp
index 6fa8ceda..4f15982b 100644
--- a/widgets/OpenGLWidgetRenderer.cpp
+++ b/widgets/OpenGLWidgetRenderer.cpp
@@ -62,6 +62,8 @@ void OpenGLWidgetRenderer::resizeGL(int w, int h)
 {
     // QGLWidget uses window()->windowHandle()->devicePixelRatio() for resizeGL(), while QOpenGLWidget does not, so scale here
 #if QT_VERSION >= QT_VERSION_CHECK(5, 5, 0)
+    if (!context())
+        return;
     const qreal dpr = context()->screen()->devicePixelRatio();
 #elif QT_VERSION >= QT_VERSION_CHECK(5, 1, 0)
     // qApp->devicePixelRatio() is global, window()->windowHandle()->devicePixelRatio() depends on screen, check window() and windowHandle() is required.
@@ -79,9 +81,9 @@ void OpenGLWidgetRenderer::resizeEvent(QResizeEvent *e)
     QOpenGLWidget::resizeEvent(e); //will call resizeGL(). TODO:will call paintEvent()?
 }
 
-void OpenGLWidgetRenderer::showEvent(QShowEvent *)
+void OpenGLWidgetRenderer::showEvent(QShowEvent *e)
 {
-    onShowEvent();
+    onShowEvent(); // TODO: onShowEvent(w, h)?
+    resizeGL(width(), height());
 }
-
 } //namespace QtAV