DolphinTabPage: Prevent re-entrant signal activation for slotViewActivated

When switching tabs with split view enabled and the filter bar visible,
a storm of activation calls is triggered and at the end signal/slot
connections for both views is a mess (no listeners, navigation buttons
linked to unfocused view etc.).

Disconnect DolphinTabPage slot when it changes its own state.

BUG: 508554, 512011, 508405, 511076, 503576

3 files changed, 98 insertions, 1 deletions

diff --git a/src/dolphintabpage.cpp b/src/dolphintabpage.cpp
index ca47130c0..f4922bf70 100644
--- a/src/dolphintabpage.cpp
+++ b/src/dolphintabpage.cpp
@@ -60,7 +60,13 @@ DolphinTabPage::DolphinTabPage(const QUrl &primaryUrl, const QUrl &secondaryUrl,
         m_secondaryViewContainer->show();
     }
 
+    // DolphinView::setActive(true) calls setFocus() then emits activated().
+    // activated() is connected to slotViewActivated() which toggles
+    // m_primaryViewActive — correct for user-initiated pane switches, but
+    // wrong here during construction. Disconnect to prevent the spurious toggle.
+    disconnectViewActivatedSignals();
     m_primaryViewContainer->setActive(true);
+    connectViewActivatedSignals();
 }
 
 bool DolphinTabPage::primaryViewActive() const
@@ -364,12 +370,22 @@ void DolphinTabPage::restoreState(const QByteArray &state)
     }
 
     stream >> m_primaryViewActive;
+    // DolphinView::setActive(true) calls setFocus() then emits activated().
+    // activated() is connected to slotViewActivated() which toggles
+    // m_primaryViewActive — correct for user-initiated pane switches, but
+    // wrong here during session restore. Disconnect to prevent the spurious toggle.
+    disconnectViewActivatedSignals();
     if (m_primaryViewActive) {
+        if (m_splitViewEnabled) {
+            m_secondaryViewContainer->setActive(false);
+        }
         m_primaryViewContainer->setActive(true);
     } else {
         Q_ASSERT(m_splitViewEnabled);
+        m_primaryViewContainer->setActive(false);
         m_secondaryViewContainer->setActive(true);
     }
+    connectViewActivatedSignals();
 
     QByteArray splitterState;
     stream >> splitterState;
@@ -393,8 +409,16 @@ void DolphinTabPage::setActive(bool active)
         // we should bypass changing active view in split mode
         m_active = !m_splitViewEnabled;
     }
-    // we want view to fire activated when goes from false to true
+    // DolphinView::setActive(true) calls setFocus() then emits activated().
+    // activated() is connected to slotViewActivated() which toggles
+    // m_primaryViewActive — correct for user-initiated pane switches, but
+    // wrong here during tab switch. Disconnect to prevent the spurious toggle.
+    disconnectViewActivatedSignals();
+    if (active && m_splitViewEnabled) {
+        inactiveViewContainer()->setActive(false);
+    }
     activeViewContainer()->setActive(active);
+    connectViewActivatedSignals();
 }
 
 void DolphinTabPage::setCustomLabel(const QString &label)
@@ -518,6 +542,22 @@ void DolphinTabPage::switchActiveView()
     }
 }
 
+void DolphinTabPage::connectViewActivatedSignals()
+{
+    connect(m_primaryViewContainer->view(), &DolphinView::activated, this, &DolphinTabPage::slotViewActivated);
+    if (m_secondaryViewContainer) {
+        connect(m_secondaryViewContainer->view(), &DolphinView::activated, this, &DolphinTabPage::slotViewActivated);
+    }
+}
+
+void DolphinTabPage::disconnectViewActivatedSignals()
+{
+    disconnect(m_primaryViewContainer->view(), &DolphinView::activated, this, &DolphinTabPage::slotViewActivated);
+    if (m_secondaryViewContainer) {
+        disconnect(m_secondaryViewContainer->view(), &DolphinView::activated, this, &DolphinTabPage::slotViewActivated);
+    }
+}
+
 DolphinViewContainer *DolphinTabPage::createViewContainer(const QUrl &url) const
 {
     DolphinViewContainer *container = new DolphinViewContainer(url, m_splitter);
diff --git a/src/dolphintabpage.h b/src/dolphintabpage.h
index b6135d360..421496ce9 100644
--- a/src/dolphintabpage.h
+++ b/src/dolphintabpage.h
@@ -204,6 +204,15 @@ private:
      */
     void startExpandViewAnimation(DolphinViewContainer *expandingContainer);
 
+    /**
+     * Connect/disconnect DolphinView::activated → slotViewActivated for all
+     * current view containers. Used to suppress the signal during programmatic
+     * activation (tab switch, construction, session restore) so that
+     * slotViewActivated does not spuriously toggle m_primaryViewActive.
+     */
+    void connectViewActivatedSignals();
+    void disconnectViewActivatedSignals();
+
 private:
     DolphinTabPageSplitter *m_splitter;
 
diff --git a/src/tests/dolphinmainwindowtest.cpp b/src/tests/dolphinmainwindowtest.cpp
index 26bb52a8e..a1727afdb 100644
--- a/src/tests/dolphinmainwindowtest.cpp
+++ b/src/tests/dolphinmainwindowtest.cpp
@@ -71,6 +71,7 @@ private Q_SLOTS:
     void testThumbnailAfterRename();
     void testViewModeAfterDynamicView();
     void testActivationAndTabTitleAfterRenameOpeningFolder();
+    void testActiveViewAfterTabSwitchWithSplitView();
     void cleanupTestCase();
 
 private:
@@ -1292,6 +1293,53 @@ void DolphinMainWindowTest::testActivationAndTabTitleAfterRenameOpeningFolder()
     QCOMPARE(tabWidget->tabText(1), expectedNewTab1Title);
 }
 
+// Test that switching tabs does not spuriously toggle which split-view pane is active.
+// Regression test for the bug where DolphinTabPage::setActive(true) during tab switch
+// caused DolphinView::activated() to reach slotViewActivated(), which toggled
+// m_primaryViewActive and connected MainWindow signals to the wrong view container.
+void DolphinMainWindowTest::testActiveViewAfterTabSwitchWithSplitView()
+{
+    m_mainWindow->openDirectories({QUrl::fromLocalFile(QDir::homePath())}, false);
+    m_mainWindow->show();
+    QVERIFY(QTest::qWaitForWindowExposed(m_mainWindow.data()));
+    QVERIFY(m_mainWindow->isVisible());
+
+    auto tabWidget = m_mainWindow->findChild<DolphinTabWidget *>("tabWidget");
+    QVERIFY(tabWidget);
+
+    // Enable split view on the first tab. After this, the secondary (right) pane
+    // becomes active via slotViewActivated(), so primaryViewActive() is false.
+    m_mainWindow->actionCollection()->action(QStringLiteral("split_view"))->trigger();
+    QVERIFY(tabWidget->currentTabPage()->splitViewEnabled());
+    QVERIFY(!tabWidget->currentTabPage()->primaryViewActive());
+    auto firstTabPage = tabWidget->currentTabPage();
+    auto firstTabSecondary = firstTabPage->secondaryViewContainer();
+    QVERIFY(firstTabSecondary->isActive());
+
+    // Open a second tab and switch to it.
+    tabWidget->openNewActivatedTab(QUrl::fromLocalFile(QDir::homePath()));
+    QCOMPARE(tabWidget->count(), 2);
+    QCOMPARE(tabWidget->currentIndex(), 1);
+
+    // Spy on activeViewChanged to count emissions during the tab switch back.
+    QSignalSpy activeViewChangedSpy(tabWidget, &DolphinTabWidget::activeViewChanged);
+
+    // Switch back to the first tab.
+    tabWidget->setCurrentIndex(0);
+    QCOMPARE(tabWidget->currentTabPage(), firstTabPage);
+
+    // activeViewChanged must be emitted exactly once — by currentTabChanged itself.
+    // A spurious second emission would indicate slotViewActivated() fired during
+    // the programmatic setActive(true) and toggled m_primaryViewActive.
+    QCOMPARE(activeViewChangedSpy.count(), 1);
+
+    // The secondary pane must still be the designated active one.
+    QVERIFY(!firstTabPage->primaryViewActive());
+    QCOMPARE(firstTabPage->activeViewContainer(), firstTabSecondary);
+    QVERIFY(firstTabSecondary->isActive());
+    QVERIFY(!firstTabPage->primaryViewContainer()->isActive());
+}
+
 void DolphinMainWindowTest::cleanupTestCase()
 {
     m_mainWindow->showNormal();