3 files changed, 73 insertions, 26 deletions

diff --git a/src/plugins/coreplugin/editormanager/editormanager.cpp b/src/plugins/coreplugin/editormanager/editormanager.cpp
index 9041d2bd4a..95eb0def6c 100644
--- a/src/plugins/coreplugin/editormanager/editormanager.cpp
+++ b/src/plugins/coreplugin/editormanager/editormanager.cpp
@@ -1724,6 +1724,8 @@ void EditorManagerPrivate::setCurrentEditor(IEditor *editor, bool ignoreNavigati
 
     updateActions();
 
+    if (QTC_GUARD(!d->m_currentView.isEmpty()) && d->m_currentView.constFirst() != previousView)
+        emit d->currentViewChanged();
     if (d->m_currentEditor != previousEditor)
         emit m_instance->currentEditorChanged(d->m_currentEditor);
 }
@@ -1742,6 +1744,8 @@ void EditorManagerPrivate::setCurrentView(EditorView *view)
             previousView->update();
         if (d->m_currentView.constFirst())
             view->update();
+
+        emit d->currentViewChanged();
     }
 
     setCurrentEditor(view->currentEditor());
@@ -1869,6 +1873,8 @@ void EditorManagerPrivate::addEditorArea(EditorArea *area)
             // If we didn't find a better view, so be it
         },
         Qt::QueuedConnection);
+    connect(area, &SplitterOrView::splitStateChanged, d, &EditorManagerPrivate::viewCountChanged);
+    emit d->viewCountChanged();
 }
 
 void EditorManagerPrivate::splitNewWindow(EditorView *view)
@@ -2280,31 +2286,33 @@ void EditorManagerPrivate::editorAreaDestroyed(QObject *area)
         }
     }
     // check if the destroyed editor area had the current view or current editor
-    if (currentEditorView())
-        return;
-    // we need to set a new current editor or view
-    if (!newActiveArea) {
-        // some window managers behave weird and don't activate another window
-        // or there might be a Qt Creator toplevel activated that doesn't have editor windows
-        newActiveArea = d->m_editorAreas.first();
-    }
-
-    // check if the focusWidget points to some view
-    SplitterOrView *focusSplitterOrView = nullptr;
-    QWidget *candidate = newActiveArea->focusWidget();
-    while (candidate && candidate != newActiveArea) {
-        if ((focusSplitterOrView = qobject_cast<SplitterOrView *>(candidate)))
-            break;
-        candidate = candidate->parentWidget();
+    if (!currentEditorView()) {
+        // we need to set a new current editor or view
+        if (!newActiveArea) {
+            // some window managers behave weird and don't activate another window
+            // or there might be a Qt Creator toplevel activated that doesn't have editor windows
+            newActiveArea = d->m_editorAreas.first();
+        }
+
+        // check if the focusWidget points to some view
+        SplitterOrView *focusSplitterOrView = nullptr;
+        QWidget *candidate = newActiveArea->focusWidget();
+        while (candidate && candidate != newActiveArea) {
+            if ((focusSplitterOrView = qobject_cast<SplitterOrView *>(candidate)))
+                break;
+            candidate = candidate->parentWidget();
+        }
+        // focusWidget might have been 0
+        if (!focusSplitterOrView)
+            focusSplitterOrView = newActiveArea->findFirstView()->parentSplitterOrView();
+        QTC_ASSERT(focusSplitterOrView, focusSplitterOrView = newActiveArea);
+        EditorView *focusView
+            = focusSplitterOrView->findFirstView(); // can be just focusSplitterOrView
+        QTC_ASSERT(focusView, focusView = newActiveArea->findFirstView());
+        if (QTC_GUARD(focusView))
+            EditorManagerPrivate::activateView(focusView);
     }
-    // focusWidget might have been 0
-    if (!focusSplitterOrView)
-        focusSplitterOrView = newActiveArea->findFirstView()->parentSplitterOrView();
-    QTC_ASSERT(focusSplitterOrView, focusSplitterOrView = newActiveArea);
-    EditorView *focusView = focusSplitterOrView->findFirstView(); // can be just focusSplitterOrView
-    QTC_ASSERT(focusView, focusView = newActiveArea->findFirstView());
-    QTC_ASSERT(focusView, return);
-    EditorManagerPrivate::activateView(focusView);
+    emit viewCountChanged();
 }
 
 void EditorManagerPrivate::autoSave()
@@ -2665,6 +2673,14 @@ QList<EditorView *> EditorManagerPrivate::allEditorViews()
     return views;
 }
 
+bool EditorManagerPrivate::hasMoreThanOneview()
+{
+    if (d->m_editorAreas.size() > 1)
+        return true;
+    QTC_ASSERT(d->m_editorAreas.size() > 0, return false);
+    return d->m_editorAreas.constFirst()->isSplitter();
+}
+
 /*!
     Returns the pointer to the instance. Only use for connecting to signals.
 */
diff --git a/src/plugins/coreplugin/editormanager/editormanager_p.h b/src/plugins/coreplugin/editormanager/editormanager_p.h
index 789acd16e1..db5bf759ae 100644
--- a/src/plugins/coreplugin/editormanager/editormanager_p.h
+++ b/src/plugins/coreplugin/editormanager/editormanager_p.h
@@ -61,6 +61,7 @@ public:
     static EditorArea *mainEditorArea();
     static EditorView *currentEditorView();
     static QList<EditorView *> allEditorViews();
+    static bool hasMoreThanOneview();
     static void setCurrentEditor(IEditor *editor, bool ignoreNavigationHistory = false);
     static IEditor *openEditor(EditorView *view,
                                const Utils::FilePath &filePath,
@@ -137,6 +138,8 @@ public slots:
 
 signals:
     void placeholderTextChanged(const QString &text);
+    void currentViewChanged();
+    void viewCountChanged();
 
 private:
     static void gotoNextDocHistory();
diff --git a/src/plugins/coreplugin/editormanager/editorview.cpp b/src/plugins/coreplugin/editormanager/editorview.cpp
index 6aa20510cb..ae9c047a77 100644
--- a/src/plugins/coreplugin/editormanager/editorview.cpp
+++ b/src/plugins/coreplugin/editormanager/editorview.cpp
@@ -14,10 +14,11 @@
 
 #include <utils/algorithm.h>
 #include <utils/infobar.h>
-#include <utils/qtcassert.h>
-#include <utils/theme/theme.h>
 #include <utils/layoutbuilder.h>
 #include <utils/link.h>
+#include <utils/overlaywidget.h>
+#include <utils/qtcassert.h>
+#include <utils/theme/theme.h>
 #include <utils/utilsicons.h>
 
 #include <QFileInfo>
@@ -125,6 +126,33 @@ EditorView::EditorView(SplitterOrView *parentSplitterOrView, QWidget *parent) :
             this, &EditorView::openDroppedFiles);
 
     updateNavigatorActions();
+
+    auto currentViewOverlay = new OverlayWidget;
+    currentViewOverlay->attachToWidget(this);
+    currentViewOverlay->setPaintFunction([this](QWidget *w, QPainter &p, QPaintEvent *) {
+        const int width = 2;
+        const QPoint margin{0, width};
+        p.setPen({w->palette().color(QPalette::Highlight), width});
+        p.drawLine(
+            m_toolBar->geometry().bottomLeft() + margin,
+            m_toolBar->geometry().bottomRight() + margin);
+    });
+    currentViewOverlay->setVisible(false);
+    const auto updateCurrentViewOverlay = [this, currentViewOverlay] {
+        currentViewOverlay->setVisible(
+            EditorManagerPrivate::hasMoreThanOneview()
+            && EditorManagerPrivate::currentEditorView() == this);
+    };
+    connect(
+        EditorManagerPrivate::instance(),
+        &EditorManagerPrivate::currentViewChanged,
+        currentViewOverlay,
+        updateCurrentViewOverlay);
+    connect(
+        EditorManagerPrivate::instance(),
+        &EditorManagerPrivate::viewCountChanged,
+        currentViewOverlay,
+        updateCurrentViewOverlay);
 }
 
 EditorView::~EditorView() = default;