LogViewForm: follow bottom of the log

Minor improvement of log viewer form: if vertical scrollbar is on the
bottom and new text is appended, scroll to bottom after appending it so
that we can still see the newest entries. If the scrollbar is not on the
bottom, preserve its position so that we can still see the same entry
(as it used to be).

2 files changed, 10 insertions, 0 deletions

diff --git a/src/gui/logviewform.cpp b/src/gui/logviewform.cpp
index fdf0f71..834496b 100644
--- a/src/gui/logviewform.cpp
+++ b/src/gui/logviewform.cpp
@@ -25,6 +25,12 @@ LogViewForm::~LogViewForm()
 	// no need to delete child widgets, Qt does it all for us
 }
 
+bool LogViewForm::isOnBottom() const
+{
+	const QScrollBar* vsb = logTextEdit->verticalScrollBar();
+	return (vsb->value() == vsb->maximum());
+}
+
 void LogViewForm::scrollToBottom()
 {
 	QScrollBar* vsb = logTextEdit->verticalScrollBar();
@@ -86,7 +92,10 @@ void LogViewForm::update(bool log_zapped)
 	if (logstream) {
 		QString s = logstream->read();
 		if (!s.isNull() && !s.isEmpty()) {
+			bool bottom = isOnBottom();
 			logTextEdit->appendPlainText(s);
+			if (bottom)
+				scrollToBottom();
 		}
 	}
 }
diff --git a/src/gui/logviewform.h b/src/gui/logviewform.h
index d91f7c6..ab4ec0b 100644
--- a/src/gui/logviewform.h
+++ b/src/gui/logviewform.h
@@ -15,6 +15,7 @@ private:
     QFile* logfile;
     QTextStream* logstream;
 
+    bool isOnBottom() const;
     void scrollToBottom();
 
 public: