Output panes: Fix auto-scrolling issue

The idea is that the user turns auto-scrolling off by manually moving the
scrollbar up and turns it back on again by moving it all the way down.
However, at least on my machine I am no longer able to do the
latter -- the scrollbar position is always at least one below the
maximum. I don't know when, why or how that changed, nor do I know
whether it's about Qt, the window system or something else. Either way,
we have to account for it.

Change-Id: I83aab758d72735d4db45d228eca8bbc7a8eebd93
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/coreplugin/outputwindow.cpp

@@ -155,6 +155,8 @@ OutputWindow::OutputWindow(Context context, const QString &settingsKey, QWidget
 
     connect(verticalScrollBar(), &QAbstractSlider::sliderMoved,
             this, &OutputWindow::updateAutoScroll);
+    connect(verticalScrollBar(), &QAbstractSlider::sliderReleased,
+            this, &OutputWindow::updateAutoScroll);
 
     undoAction->setEnabled(false);
     redoAction->setEnabled(false);
@@ -449,7 +451,7 @@ void OutputWindow::handleOutputChunk(const QString &output, OutputFormat format)
 
 void OutputWindow::updateAutoScroll()
 {
-    d->scrollToBottom = isScrollbarAtBottom();
+    d->scrollToBottom = verticalScrollBar()->value() >= verticalScrollBar()->maximum() - 1;
 }
 
 void OutputWindow::setMaxCharCount(int count)
@@ -473,11 +475,6 @@ void OutputWindow::appendMessage(const QString &output, OutputFormat format)
         d->queueTimer.start();
 }
 
-bool OutputWindow::isScrollbarAtBottom() const
-{
-    return verticalScrollBar()->value() == verticalScrollBar()->maximum();
-}
-
 QMimeData *OutputWindow::createMimeDataFromSelection() const
 {
     const auto mimeData = new QMimeData;

src/plugins/coreplugin/outputwindow.h

@@ -91,7 +91,6 @@ public slots:
     void setWordWrapEnabled(bool wrap);
 
 protected:
-    bool isScrollbarAtBottom() const;
     virtual void handleLink(const QPoint &pos);
 
 private: