remember scroll position when reloading msg

src/librssguard/gui/messagebrowser.cpp

@@ -192,3 +192,11 @@ void MessageBrowser::loadMessage(const Message& message, RootItem* root) {
   m_txtBrowser->verticalScrollBar()->triggerAction(QScrollBar::SliderToMinimum);
   m_searchWidget->hide();
 }
+
+double MessageBrowser::verticalScrollBarPosition() const {
+  return m_txtBrowser->verticalScrollBar()->value();
+}
+
+void MessageBrowser::setVerticalScrollBarPosition(double pos) {
+  m_txtBrowser->verticalScrollBar()->setValue(pos);
+}

src/librssguard/gui/messagebrowser.h

@@ -22,7 +22,10 @@ class MessageBrowser : public QWidget {
   public:
     explicit MessageBrowser(QWidget* parent = nullptr);
 
+    double verticalScrollBarPosition() const;
+
   public slots:
+    void setVerticalScrollBarPosition(double pos);
     void clear();
     void reloadFontSettings();
     void loadMessage(const Message& message, RootItem* root);

src/librssguard/gui/messagepreviewer.cpp

@@ -12,6 +12,7 @@
 
 #if defined (USE_WEBENGINE)
 #include "gui/webbrowser.h"
+#include "gui/webviewer.h"
 #else
 #include "gui/messagebrowser.h"
 #endif
@@ -41,7 +42,7 @@ void MessagePreviewer::createConnections() {
 }
 
 MessagePreviewer::MessagePreviewer(QWidget* parent)
-  : QWidget(parent), m_layout(new QGridLayout(this)), m_toolBar(new QToolBar(this)) {
+  : QWidget(parent), m_layout(new QGridLayout(this)), m_toolBar(new QToolBar(this)), m_verticalScrollBarPosition(0.0) {
 #if defined (USE_WEBENGINE)
   m_txtMessage = new WebBrowser(this);
 #else
@@ -75,6 +76,10 @@ WebBrowser* MessagePreviewer::webBrowser() const {
 void MessagePreviewer::clear() {
   m_txtMessage->clear();
   hide();
+
+  m_verticalScrollBarPosition = 0.0;
+  m_root.clear();
+  m_message = Message();
 }
 
 void MessagePreviewer::hideToolbar() {
@@ -82,6 +87,10 @@ void MessagePreviewer::hideToolbar() {
 }
 
 void MessagePreviewer::loadMessage(const Message& message, RootItem* root) {
+  m_verticalScrollBarPosition = m_txtMessage->verticalScrollBarPosition();
+
+  bool same_message = message.m_id == m_message.m_id && m_root == root;
+
   m_message = message;
   m_root = root;
 
@@ -90,6 +99,10 @@ void MessagePreviewer::loadMessage(const Message& message, RootItem* root) {
     show();
     m_actionSwitchImportance->setChecked(m_message.m_isImportant);
     m_txtMessage->loadMessage(message, root);
+
+    if (same_message) {
+      m_txtMessage->setVerticalScrollBarPosition(m_verticalScrollBarPosition);
+    }
   }
 }
 

src/librssguard/gui/messagepreviewer.h

@@ -61,6 +61,7 @@ class MessagePreviewer : public QWidget {
     MessageBrowser* m_txtMessage;
 #endif
 
+    double m_verticalScrollBarPosition;
     Message m_message;
     QPointer<RootItem> m_root;
     QAction* m_actionMarkRead;

src/librssguard/gui/messagesview.h

@@ -77,6 +77,7 @@ class MessagesView : public QTreeView {
     // Notify others about message selections.
     void currentMessageChanged(const Message& message, RootItem* root);
     void currentMessageRemoved();
+    void willReselectSameMessage();
 
   private:
     void sort(int column, Qt::SortOrder order, bool repopulate_data, bool change_header, bool emit_changed_from_header);

src/librssguard/gui/webbrowser.cpp

@@ -88,13 +88,33 @@ WebBrowser::~WebBrowser() {
   delete m_layout;
 }
 
+double WebBrowser::verticalScrollBarPosition() const {
+  double position;
+  QEventLoop loop;
+
+  viewer()->page()->runJavaScript(QSL("window.pageYOffset;"), [&position, &loop](const QVariant& val) {
+    position = val.toDouble();
+    loop.exit();
+  });
+  loop.exec();
+
+  return position;
+}
+
+void WebBrowser::setVerticalScrollBarPosition(double pos) {
+  viewer()->page()->runJavaScript(QSL("window.scrollTo(0, %1);").arg(pos));
+}
+
 void WebBrowser::reloadFontSettings() {
   QFont fon;
 
   fon.fromString(qApp->settings()->value(GROUP(Messages),
                                          SETTING(Messages::PreviewerFontStandard)).toString());
-  QWebEngineSettings::globalSettings()->setFontFamily(QWebEngineSettings::StandardFont, fon.family());
-  QWebEngineSettings::globalSettings()->setFontSize(QWebEngineSettings::DefaultFontSize, fon.pointSize());
+
+  QWebEngineSettings::defaultSettings()->setFontFamily(QWebEngineSettings::StandardFont, fon.family());
+  QWebEngineSettings::defaultSettings()->setFontFamily(QWebEngineSettings::SerifFont, fon.family());
+  QWebEngineSettings::defaultSettings()->setFontFamily(QWebEngineSettings::SansSerifFont, fon.family());
+  QWebEngineSettings::defaultSettings()->setFontSize(QWebEngineSettings::DefaultFontSize, fon.pointSize());
 }
 
 void WebBrowser::increaseZoom() {

src/librssguard/gui/webbrowser.h

@@ -34,7 +34,10 @@ class WebBrowser : public TabContent {
     WebBrowser* webBrowser() const;
     WebViewer* viewer() const;
 
+    double verticalScrollBarPosition() const;
+
   public slots:
+    void setVerticalScrollBarPosition(double pos);
     void reloadFontSettings();
 
     void increaseZoom();