From 29dea7f3173783a97f85d84623241d8dc388c701 Mon Sep 17 00:00:00 2001
From: Friedemann Kleint <Friedemann.Kleint@qt.io>
Date: Tue, 4 May 2021 14:35:39 +0200
Subject: [PATCH] QMdiArea: Fix top level window title when using
 DontMaximizeSubWindowOnActivation

When trying to find the original window title, check for another
maximized sub window and use its title. Protect the calls to
setWindowTitle to prevent the original title from being cleared.

Fixes: QTBUG-92240
Change-Id: I55175382ab261b4cf8b5528304adaaec4fbe2c31
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
(cherry picked from commit 8886462872db9cdab4d7683823fd24fb9f8920c4)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/widgets/widgets/qmdisubwindow.cpp         | 31 +++++++++++--
 src/widgets/widgets/qmdisubwindow_p.h         |  1 +
 .../widgets/widgets/qmdiarea/tst_qmdiarea.cpp | 43 ++++++++++++++++++-
 3 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/src/widgets/widgets/qmdisubwindow.cpp b/src/widgets/widgets/qmdisubwindow.cpp
index 89d77574f09..1c03b02ab80 100644
--- a/src/widgets/widgets/qmdisubwindow.cpp
+++ b/src/widgets/widgets/qmdisubwindow.cpp
@@ -263,11 +263,28 @@ static inline ControlElement<T> *ptr(QWidget *widget)
     return nullptr;
 }
 
+QString QMdiSubWindowPrivate::originalWindowTitleHelper() const
+{
+    Q_Q(const QMdiSubWindow);
+    // QTBUG-92240: When DontMaximizeSubWindowOnActivation is set and
+    // there is another subwindow maximized, use its original title.
+    if (auto *mdiArea = q->mdiArea()) {
+        const auto &subWindows = mdiArea->subWindowList();
+        for (auto *subWindow : subWindows) {
+            if (subWindow != q && subWindow->isMaximized()) {
+                auto *subWindowD = static_cast<QMdiSubWindowPrivate *>(qt_widget_private(subWindow));
+                if (!subWindowD->originalTitle.isNull())
+                    return subWindowD->originalTitle;
+            }
+        }
+    }
+    return q->window()->windowTitle();
+}
+
 QString QMdiSubWindowPrivate::originalWindowTitle()
 {
-    Q_Q(QMdiSubWindow);
     if (originalTitle.isNull()) {
-        originalTitle = q->window()->windowTitle();
+        originalTitle = originalWindowTitleHelper();
         if (originalTitle.isNull())
             originalTitle = QLatin1String("");
     }
@@ -282,11 +299,17 @@ void QMdiSubWindowPrivate::setNewWindowTitle()
         return;
     QString original = originalWindowTitle();
     if (!original.isEmpty()) {
-        if (!original.contains(QMdiSubWindow::tr("- [%1]").arg(childTitle)))
-            q->window()->setWindowTitle(QMdiSubWindow::tr("%1 - [%2]").arg(original, childTitle));
+        if (!original.contains(QMdiSubWindow::tr("- [%1]").arg(childTitle))) {
+            auto title = QMdiSubWindow::tr("%1 - [%2]").arg(original, childTitle);
+            ignoreWindowTitleChange = true;
+            q->window()->setWindowTitle(title);
+            ignoreWindowTitleChange = false;
+        }
 
     } else {
+        ignoreWindowTitleChange = true;
         q->window()->setWindowTitle(childTitle);
+        ignoreWindowTitleChange = false;
     }
 }
 
diff --git a/src/widgets/widgets/qmdisubwindow_p.h b/src/widgets/widgets/qmdisubwindow_p.h
index d3513b6708c..043cf922012 100644
--- a/src/widgets/widgets/qmdisubwindow_p.h
+++ b/src/widgets/widgets/qmdisubwindow_p.h
@@ -286,6 +286,7 @@ public:
 #endif
     void updateInternalWindowTitle();
     QString originalWindowTitle();
+    QString originalWindowTitleHelper() const;
     void setNewWindowTitle();
 
     inline int titleBarHeight() const
diff --git a/tests/auto/widgets/widgets/qmdiarea/tst_qmdiarea.cpp b/tests/auto/widgets/widgets/qmdiarea/tst_qmdiarea.cpp
index 6df7c74bdc8..225b349f081 100644
--- a/tests/auto/widgets/widgets/qmdiarea/tst_qmdiarea.cpp
+++ b/tests/auto/widgets/widgets/qmdiarea/tst_qmdiarea.cpp
@@ -1,4 +1,4 @@
-/****************************************************************************
+/****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
@@ -281,6 +281,8 @@ private slots:
     void nativeSubWindows();
     void task_209615();
     void task_236750();
+    void qtbug92240_title_data();
+    void qtbug92240_title();
 
 private:
     QMdiSubWindow *activeWindow;
@@ -2697,6 +2699,45 @@ void tst_QMdiArea::task_236750()
     subWindow->showMinimized();
 }
 
+// QTBUG-92240: When subwindows are maximized, their title is supposed to
+// appear on the main window. When DontMaximizeSubWindowOnActivation was set,
+// titles of previously created maximized windows interfered, resulting in
+// "QTBUG-92240 - [1] - [2]".
+void tst_QMdiArea::qtbug92240_title_data()
+{
+    QTest::addColumn<bool>("dontMaximize");
+    QTest::newRow("default") << false;
+    QTest::newRow("dontMaximize") << true;
+}
+
+void tst_QMdiArea::qtbug92240_title()
+{
+    QFETCH(bool, dontMaximize);
+
+#ifdef Q_OS_MACOS
+    QSKIP("Not supported on macOS");
+#endif
+
+    QMainWindow w;
+    const QString title = QStringLiteral("QTBUG-92240");
+    w.setWindowTitle(title);
+    w.menuBar()->addMenu(QStringLiteral("File"));
+    w.show();
+
+    auto *mdiArea = new QMdiArea;
+    w.setCentralWidget(mdiArea);
+    if (dontMaximize)
+        mdiArea->setOption(QMdiArea::DontMaximizeSubWindowOnActivation);
+    auto *sw1 = mdiArea->addSubWindow(new QWidget);
+    sw1->setWindowTitle(QStringLiteral("1"));
+    sw1->showMaximized();
+    QTRY_COMPARE(w.windowTitle(), QLatin1String("QTBUG-92240 - [1]"));
+    auto *sw2 = mdiArea->addSubWindow(new QWidget);
+    sw2->setWindowTitle(QStringLiteral("2"));
+    sw2->showMaximized();
+    QTRY_COMPARE(w.windowTitle(), QLatin1String("QTBUG-92240 - [2]"));
+}
+
 QTEST_MAIN(tst_QMdiArea)
 #include "tst_qmdiarea.moc"