From 1ea73bc29b7542141bfcfa138cc194404c283bd5 Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.agocs@qt.io>
Date: Thu, 10 Mar 2022 15:14:43 +0100
Subject: [PATCH] Fix losing QOpenGLWidget paints when a child widget is
 invisible
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Pick-to: 6.3 6.2
Change-Id: I136b486d30e31acadd6b1b837dc7e834ee3e23fb
Fixes: QTBUG-101620
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Christian Strømme <christian.stromme@qt.io>
---
 src/widgets/kernel/qwidget.cpp                |  7 ++++++
 .../qopenglwidget/tst_qopenglwidget.cpp       | 25 +++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 1527ec679f..3918a46da4 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -11049,6 +11049,13 @@ void QWidgetPrivate::update(T r)
 {
     Q_Q(QWidget);
 
+#ifndef QT_NO_OPENGL
+    if (renderToTexture && !q->isVisible()) {
+        renderToTextureReallyDirty = 1;
+        return;
+    }
+#endif
+
     if (!q->isVisible() || !q->updatesEnabled())
         return;
 
diff --git a/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp b/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp
index 3d7bb36f24..12ea9e6eef 100644
--- a/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp
+++ b/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp
@@ -66,6 +66,7 @@ private slots:
     void stackWidgetOpaqueChildIsVisible();
     void offscreen();
     void offscreenThenOnscreen();
+    void paintWhileHidden();
 
 #ifdef QT_BUILD_INTERNAL
     void staticTextDanglingPointer();
@@ -694,6 +695,30 @@ void tst_QOpenGLWidget::offscreenThenOnscreen()
     QVERIFY(image.pixel(30, 40) == qRgb(0, 0, 255));
 }
 
+void tst_QOpenGLWidget::paintWhileHidden()
+{
+    QScopedPointer<QWidget> tlw(new QWidget);
+    tlw->resize(640, 480);
+
+    ClearWidget *w = new ClearWidget(0, 640, 480);
+    w->setParent(tlw.data());
+    w->setClearColor(0, 0, 1);
+
+    tlw->show();
+    QVERIFY(QTest::qWaitForWindowExposed(tlw.data()));
+
+    // QTBUG-101620: Now make visible=false and call update and see if we get to
+    // paintEvent/paintGL eventually, to ensure the updating of the texture is
+    // not optimized permanently away even though there is no composition
+    // on-screen at the point when update() is called.
+
+    w->setVisible(false);
+    w->m_paintCalled = 0;
+    w->update();
+    w->setVisible(true);
+    QTRY_VERIFY(w->m_paintCalled > 0);
+}
+
 class StaticTextPainterWidget : public QOpenGLWidget
 {
 public: