1 files changed, 118 insertions, 1 deletions

diff --git a/tests/auto/widgets/kernel/qwidgetrepaintmanager/tst_qwidgetrepaintmanager.cpp b/tests/auto/widgets/kernel/qwidgetrepaintmanager/tst_qwidgetrepaintmanager.cpp
index 52b179fedb..490c2a7d8c 100644
--- a/tests/auto/widgets/kernel/qwidgetrepaintmanager/tst_qwidgetrepaintmanager.cpp
+++ b/tests/auto/widgets/kernel/qwidgetrepaintmanager/tst_qwidgetrepaintmanager.cpp
@@ -29,7 +29,8 @@
 
 #include <QTest>
 #include <QPainter>
-#include <QWidget>
+#include <QScrollArea>
+#include <QScrollBar>
 #include <QApplication>
 
 #include <private/qhighdpiscaling_p.h>
@@ -94,6 +95,7 @@ private slots:
     void opaqueChildren();
     void staticContents();
     void scroll();
+    void moveWithOverlap();
 
 private:
     const int m_fuzz;
@@ -246,5 +248,120 @@ void tst_QWidgetRepaintManager::scroll()
     QCOMPARE(widget.takePaintedRegions(), QRegion());
 }
 
+
+/*!
+    Verify that overlapping children are repainted correctly when
+    a widget is moved (via a scroll area) for such a distance that
+    none of the old area is still visible. QTBUG-26269
+*/
+void tst_QWidgetRepaintManager::moveWithOverlap()
+{
+    if (QStringList{"android"}.contains(QGuiApplication::platformName()))
+        QSKIP("This test fails on Android");
+
+    class MainWindow : public QWidget
+    {
+    public:
+        MainWindow(QWidget *parent = 0)
+            : QWidget(parent, Qt::WindowStaysOnTopHint)
+        {
+            m_scrollArea = new QScrollArea(this);
+            QWidget *w = new QWidget;
+            w->setPalette(QPalette(Qt::gray));
+            w->setAutoFillBackground(true);
+            m_scrollArea->setWidget(w);
+            m_scrollArea->resize(500, 100);
+            w->resize(5000, 600);
+
+            m_topWidget = new QWidget(this);
+            m_topWidget->setPalette(QPalette(Qt::red));
+            m_topWidget->setAutoFillBackground(true);
+            m_topWidget->resize(300, 200);
+        }
+
+        void resizeEvent(QResizeEvent *e) override
+        {
+            QWidget::resizeEvent(e);
+            // move scroll area and top widget to the center of the main window
+            scrollArea()->move((width() - scrollArea()->width()) / 2, (height() - scrollArea()->height()) / 2);
+            topWidget()->move((width() - topWidget()->width()) / 2, (height() - topWidget()->height()) / 2);
+        }
+
+
+        inline QScrollArea *scrollArea() const { return m_scrollArea; }
+        inline QWidget *topWidget() const { return m_topWidget; }
+
+        bool grabWidgetBackground(QWidget *w)
+        {
+            // To check widget's background we should compare two screenshots:
+            // the first one is taken by system tools through QScreen::grabWindow(),
+            // the second one is taken by Qt rendering to a pixmap via QWidget::grab().
+
+            QScreen *screen = w->screen();
+            const QRect screenGeometry = screen->geometry();
+            QPoint globalPos = w->mapToGlobal(QPoint(0, 0));
+            if (globalPos.x() >= screenGeometry.width())
+                globalPos.rx() -= screenGeometry.x();
+            if (globalPos.y() >= screenGeometry.height())
+                globalPos.ry() -= screenGeometry.y();
+
+            return QTest::qWaitFor([&]{
+                QImage systemScreenshot = screen->grabWindow(winId(),
+                                                             globalPos.x(), globalPos.y(),
+                                                             w->width(), w->height()).toImage();
+                systemScreenshot = systemScreenshot.convertToFormat(QImage::Format_RGB32);
+                QImage qtScreenshot = w->grab().toImage().convertToFormat(systemScreenshot.format());
+                return systemScreenshot == qtScreenshot;
+            });
+        };
+
+    private:
+        QScrollArea *m_scrollArea;
+        QWidget *m_topWidget;
+    };
+
+    MainWindow w;
+    w.showFullScreen();
+
+    QVERIFY(QTest::qWaitForWindowActive(&w));
+
+    bool result = w.grabWidgetBackground(w.topWidget());
+    // if this fails already, then the system we test on can't compare screenshots from grabbed widgets,
+    // and we have to skip this test. Possible reasons are that showing the window took too long, differences
+    // in surface formats, or unrelated bugs in QScreen::grabWindow.
+    if (!result)
+        QSKIP("Cannot compare QWidget::grab with QScreen::grabWindow on this machine");
+
+    // scroll the horizontal slider to the right side
+    {
+        w.scrollArea()->horizontalScrollBar()->setValue(w.scrollArea()->horizontalScrollBar()->maximum());
+        QVERIFY(w.grabWidgetBackground(w.topWidget()));
+    }
+
+    // scroll the vertical slider down
+    {
+        w.scrollArea()->verticalScrollBar()->setValue(w.scrollArea()->verticalScrollBar()->maximum());
+        QVERIFY(w.grabWidgetBackground(w.topWidget()));
+    }
+
+    // hide the top widget
+    {
+        w.topWidget()->hide();
+        QVERIFY(w.grabWidgetBackground(w.scrollArea()->viewport()));
+    }
+
+    // scroll the horizontal slider to the left side
+    {
+        w.scrollArea()->horizontalScrollBar()->setValue(w.scrollArea()->horizontalScrollBar()->minimum());
+        QVERIFY(w.grabWidgetBackground(w.scrollArea()->viewport()));
+    }
+
+    // scroll the vertical slider up
+    {
+        w.scrollArea()->verticalScrollBar()->setValue(w.scrollArea()->verticalScrollBar()->minimum());
+        QVERIFY(w.grabWidgetBackground(w.scrollArea()->viewport()));
+    }
+}
+
 QTEST_MAIN(tst_QWidgetRepaintManager)
 #include "tst_qwidgetrepaintmanager.moc"