From d5e0fca4909b44042ae01bd1983efd9169752cf0 Mon Sep 17 00:00:00 2001
From: Adriaan de Groot <groot@kde.org>
Date: Mon, 14 Mar 2022 16:28:44 +0100
Subject: [PATCH] [libcalamaresui] Allow starting and stopping the
 log-follower.

---
 .../viewpages/ExecutionViewStep.cpp            | 12 +++++++++++-
 src/libcalamaresui/widgets/LogWidget.cpp       | 18 ++++++++++++++++++
 src/libcalamaresui/widgets/LogWidget.h         |  9 ++++++++-
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/libcalamaresui/viewpages/ExecutionViewStep.cpp b/src/libcalamaresui/viewpages/ExecutionViewStep.cpp
index 4cf9a06a0..b227971fb 100644
--- a/src/libcalamaresui/viewpages/ExecutionViewStep.cpp
+++ b/src/libcalamaresui/viewpages/ExecutionViewStep.cpp
@@ -228,12 +228,22 @@ ExecutionViewStep::updateFromJobQueue( qreal percent, const QString& message )
 void
 ExecutionViewStep::toggleLog()
 {
-    m_tab_widget->setCurrentIndex( ( m_tab_widget->currentIndex() + 1 ) % m_tab_widget->count() );
+    const bool logBecomesVisible = m_tab_widget->currentIndex() == 0;  // ie. is not visible right now
+    if ( logBecomesVisible )
+    {
+        m_log_widget->start();
+    }
+    else
+    {
+        m_log_widget->stop();
+    }
+    m_tab_widget->setCurrentIndex( logBecomesVisible ? 1 : 0 );
 }
 
 void
 ExecutionViewStep::onLeave()
 {
+    m_log_widget->stop();
     m_slideshow->changeSlideShowState( Slideshow::Stop );
 }
 
diff --git a/src/libcalamaresui/widgets/LogWidget.cpp b/src/libcalamaresui/widgets/LogWidget.cpp
index 7a253b78c..8e559be7d 100644
--- a/src/libcalamaresui/widgets/LogWidget.cpp
+++ b/src/libcalamaresui/widgets/LogWidget.cpp
@@ -70,6 +70,7 @@ LogWidget::LogWidget( QWidget* parent )
 
     connect( &m_log_thread, &LogThread::onLogChunk, this, &LogWidget::handleLogChunk );
 
+    m_log_thread.setPriority( QThread::LowestPriority );
     m_log_thread.start();
 }
 
@@ -81,4 +82,21 @@ LogWidget::handleLogChunk( const QString& logChunk )
     m_text->ensureCursorVisible();
 }
 
+void
+LogWidget::start()
+{
+    if ( !m_log_thread.isRunning() )
+    {
+        m_text->clear();
+        m_log_thread.start();
+    }
+}
+
+void
+LogWidget::stop()
+{
+    m_log_thread.requestInterruption();
+}
+
+
 }  // namespace Calamares
diff --git a/src/libcalamaresui/widgets/LogWidget.h b/src/libcalamaresui/widgets/LogWidget.h
index 2d0ef9ab5..2abb07596 100644
--- a/src/libcalamaresui/widgets/LogWidget.h
+++ b/src/libcalamaresui/widgets/LogWidget.h
@@ -18,7 +18,7 @@ public:
     explicit LogThread( QObject* parent = nullptr );
     ~LogThread() override;
 
-signals:
+Q_SIGNALS:
     void onLogChunk( const QString& logChunk );
 };
 
@@ -32,7 +32,14 @@ class LogWidget : public QWidget
 public:
     explicit LogWidget( QWidget* parent = nullptr );
 
+public Q_SLOTS:
+    /// @brief Called by the thread when there is new data
     void handleLogChunk( const QString& logChunk );
+
+    /// @brief Stop watching for log data
+    void stop();
+    /// @brief Start watching for new log data
+    void start();
 };
 
 }  // namespace Calamares