Highlight lines coming into view

Add a profile option that would, when enabled, highlight the lines that are
coming into view. A thin blue line on the left of the terminal will highlight
the new lines in the following situations:
- scrolling with the mouse
- using the scroll bar
- using the keyboard to move up/down
- new lines resulting from the output of a command

src/EditProfileDialog.cpp

@@ -1587,6 +1587,12 @@ void EditProfileDialog::setupScrollingPage(const Profile::Ptr &profile)
 
     setupRadio(pageamounts, scrollFullPage);
 
+
+    const auto options = QVector<BooleanOption>{
+        {_scrollingUi->highlightScrolledLinesButton, Profile::HighlightScrolledLines, SLOT(toggleHighlightScrolledLines(bool))}
+    };
+    setupCheckBoxes(options, profile);
+
     // signals and slots
     connect(_scrollingUi->historySizeWidget, &Konsole::HistorySizeWidget::historySizeChanged, this,
             &Konsole::EditProfileDialog::historySizeChanged);
@@ -1612,6 +1618,11 @@ void EditProfileDialog::scrollHalfPage()
     updateTempProfileProperty(Profile::ScrollFullPage, Enum::ScrollPageHalf);
 }
 
+void EditProfileDialog::toggleHighlightScrolledLines(bool enable)
+{
+    updateTempProfileProperty(Profile::HighlightScrolledLines, enable);
+}
+
 void EditProfileDialog::setupMousePage(const Profile::Ptr &profile)
 {
     const auto options = QVector<BooleanOption>{

src/EditProfileDialog.h

@@ -176,6 +176,7 @@ private Q_SLOTS:
 
     void scrollFullPage();
     void scrollHalfPage();
+    void toggleHighlightScrolledLines(bool enable);
 
     // keyboard page
     void editKeyBinding();

src/EditProfileScrollingPage.ui

@@ -189,6 +189,45 @@
        </attribute>
       </widget>
      </item>
+     <item row="8" column="1">
+      <spacer>
+       <property name="orientation">
+        <enum>Qt::Vertical</enum>
+       </property>
+       <property name="sizeType">
+        <enum>QSizePolicy::Fixed</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>20</width>
+         <height>16</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+     <item row="9" column="0" alignment="Qt::AlignRight|Qt::AlignVCenter">
+      <widget class="QLabel" name="label">
+       <property name="sizePolicy">
+        <sizepolicy hsizetype="Fixed" vsizetype="Preferred">
+         <horstretch>0</horstretch>
+         <verstretch>0</verstretch>
+        </sizepolicy>
+       </property>
+       <property name="text">
+        <string>Highlighting:</string>
+       </property>
+       <property name="alignment">
+        <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+       </property>
+      </widget>
+     </item>
+     <item row="9" column="1">
+      <widget class="QCheckBox" name="highlightScrolledLinesButton">
+       <property name="text">
+        <string>Highlight the lines coming into view</string>
+       </property>
+      </widget>
+     </item>
     </layout>
    </item>
    <item>

src/Profile.cpp

@@ -93,6 +93,7 @@ const Profile::PropertyInfo Profile::DefaultPropertyNames[] = {
     , { HistorySize , "HistorySize" , SCROLLING_GROUP , QVariant::Int }
     , { ScrollBarPosition , "ScrollBarPosition" , SCROLLING_GROUP , QVariant::Int }
     , { ScrollFullPage , "ScrollFullPage" , SCROLLING_GROUP , QVariant::Bool }
+    , { HighlightScrolledLines , "HighlightScrolledLines" , SCROLLING_GROUP , QVariant::Bool }
 
     // Terminal Features
     , { UrlHintsModifiers , "UrlHintsModifiers" , TERMINAL_GROUP , QVariant::Int }
@@ -188,6 +189,7 @@ void Profile::useFallback()
     setProperty(HistorySize, 1000);
     setProperty(ScrollBarPosition, Enum::ScrollBarRight);
     setProperty(ScrollFullPage, false);
+    setProperty(HighlightScrolledLines, true);
 
     setProperty(FlowControlEnabled, true);
     setProperty(UrlHintsModifiers, 0);

src/Profile.h

@@ -152,6 +152,10 @@ public:
          * height or half height.
              */
         ScrollFullPage,
+        /** (bool) Specifies whether the the lines that are scrolled into view
+         * should be highlighted.
+             */
+        HighlightScrolledLines,
         /** (bool) Specifies whether the terminal will enable Bidirectional
          * text display
          */

src/TerminalDisplay.cpp

@@ -1264,8 +1264,11 @@ void TerminalDisplay::updateImage()
         dirtyRegion |= QRect(0, _contentRect.top() + (_screenWindow->currentResultLine() - _screenWindow->currentLine()) * _fontHeight,
                              _columns * _fontWidth, _fontHeight);
     }
-    _screenWindow->resetScrollCount();
 
+    if (_highlightScrolledLinesControl.enabled) {
+        dirtyRegion |= highlightScrolledLinesRegion();
+    }
+    _screenWindow->resetScrollCount();
 
     // update the parts of the display which have changed
     update(dirtyRegion);
@@ -1333,6 +1336,7 @@ void TerminalDisplay::paintEvent(QPaintEvent* pe)
         drawContents(paint, rect);
     }
     drawCurrentResultRect(paint);
+    highlightScrolledLines(paint);
     drawInputMethodPreeditString(paint, preeditRect());
     paintFilters(paint);
 
@@ -1767,6 +1771,75 @@ void TerminalDisplay::drawCurrentResultRect(QPainter& painter)
     painter.fillRect(_searchResultRect, QColor(0, 0, 255, 80));
 }
 
+void TerminalDisplay::highlightScrolledLines(QPainter& painter)
+{
+    if (!_highlightScrolledLinesControl.enabled) {
+        return;
+    }
+
+    QColor color = QColor(_colorTable[Color4Index]);
+    color.setAlpha(_highlightScrolledLinesControl.timer->isActive() ? 255 : 150);
+    painter.fillRect(_highlightScrolledLinesControl.rect, color);
+}
+
+QRect TerminalDisplay::highlightScrolledLinesRegion()
+{
+    QRect result;
+
+    if (_scrollBar->maximum() == 0) {
+        // De-highlight when entering something like 'vim'
+        if (!_highlightScrolledLinesControl.rect.isEmpty()) {
+            result = _highlightScrolledLinesControl.rect;
+            _highlightScrolledLinesControl.rect.setRect(0, 0, 0, 0);
+        }
+    } else {
+        const int highlightLeftPosition = _scrollbarLocation == Enum::ScrollBarLeft ? _scrollBar->width() : 0;
+
+        if (_highlightScrolledLinesControl.previousScrollCount != 0) {
+            // De-highlight previously scrolled lines
+            if (_screenWindow->scrollCount() == 0 && _scrollBar->value() == _scrollBar->maximum()) {
+                // Nothing has moved, we can reuse _highlightScrolledLinesControl.rect to clear
+                result = _highlightScrolledLinesControl.rect;
+                _highlightScrolledLinesControl.rect.setRect(0, 0, 0, 0);
+            } else {
+                int start = 0;
+                const int nb_lines = abs(_highlightScrolledLinesControl.previousScrollCount);
+                if (_screenWindow->scrollCount() * _highlightScrolledLinesControl.previousScrollCount > 0) {
+                    start = _screenWindow->scrollCount() < 0 ? abs(_screenWindow->scrollCount()) :
+                            _screenWindow->windowLines() - _screenWindow->scrollCount() - _highlightScrolledLinesControl.previousScrollCount;
+                } else {
+                    start = _highlightScrolledLinesControl.previousScrollCount > 0 ? _screenWindow->windowLines() - _highlightScrolledLinesControl.previousScrollCount : 0;
+                }
+                result = QRect(highlightLeftPosition, _contentRect.top() + start * _fontHeight, HIGHLIGHT_SCROLLED_LINES_WIDTH, nb_lines * _fontHeight);
+            }
+        }
+
+        // Highlight the new lines coming into view
+        int nb_lines = abs(_screenWindow->scrollCount());
+        if (nb_lines > 0) {
+            if (_highlightScrolledLinesControl.timer->isActive() && (_screenWindow->scrollCount() * _highlightScrolledLinesControl.previousScrollCount > 0)) {
+                nb_lines += abs(_highlightScrolledLinesControl.previousScrollCount);
+                nb_lines = std::min(nb_lines, _screenWindow->windowLines());
+                _highlightScrolledLinesControl.previousScrollCount += _screenWindow->scrollCount();
+            } else {
+                _highlightScrolledLinesControl.previousScrollCount = _screenWindow->scrollCount();
+            }
+            const int start = _screenWindow->scrollCount() > 0 ? std::max(_screenWindow->windowLines() - nb_lines, 0) : 0;
+            _highlightScrolledLinesControl.rect.setRect(highlightLeftPosition, _contentRect.top() + start * _fontHeight,
+                                                        HIGHLIGHT_SCROLLED_LINES_WIDTH, nb_lines * _fontHeight);
+            result |= _highlightScrolledLinesControl.rect;
+            _highlightScrolledLinesControl.timer->start();
+        }
+    }
+
+    return result;
+}
+
+void TerminalDisplay::highlightScrolledLinesEvent()
+{
+    update(_highlightScrolledLinesControl.rect);
+}
+
 QRect TerminalDisplay::imageToWidget(const QRect& imageArea) const
 {
     QRect result;
@@ -2002,7 +2075,8 @@ void TerminalDisplay::calcGeometry()
         contentsRect().height() - headerHeight // height
     );
 
-    _contentRect = contentsRect().adjusted(_margin, _margin, -_margin, -_margin);
+    _contentRect = contentsRect().adjusted(_margin + (_highlightScrolledLinesControl.enabled ? HIGHLIGHT_SCROLLED_LINES_WIDTH : 0), _margin,
+                                           -_margin - (_highlightScrolledLinesControl.enabled ? HIGHLIGHT_SCROLLED_LINES_WIDTH : 0), -_margin);
 
     switch (_scrollbarLocation) {
     case Enum::ScrollBarHidden :
@@ -2161,6 +2235,19 @@ bool TerminalDisplay::scrollFullPage() const
     return _scrollFullPage;
 }
 
+void TerminalDisplay::setHighlightScrolledLines(bool highlight)
+{
+    _highlightScrolledLinesControl.enabled = highlight;
+
+    if (_highlightScrolledLinesControl.enabled && _highlightScrolledLinesControl.timer == nullptr) {
+        // setup timer for diming the highlight on scrolled lines
+        _highlightScrolledLinesControl.timer = new QTimer(this);
+        _highlightScrolledLinesControl.timer->setSingleShot(true);
+        _highlightScrolledLinesControl.timer->setInterval(250);
+        connect(_highlightScrolledLinesControl.timer, &QTimer::timeout, this, &Konsole::TerminalDisplay::highlightScrolledLinesEvent);
+    }
+}
+
 /* ------------------------------------------------------------------------- */
 /*                                                                           */
 /*                                  Mouse                                    */
@@ -4064,6 +4151,9 @@ void TerminalDisplay::applyProfile(const Profile::Ptr &profile)
     setMiddleClickPasteMode(Enum::MiddleClickPasteModeEnum(profile->property<int>(Profile::MiddleClickPasteMode)));
     setCopyTextAsHTML(profile->property<bool>(Profile::CopyTextAsHTML));
 
+    // highlight lines scrolled into view (must be applied before margin/center)
+    setHighlightScrolledLines(profile->property<bool>(Profile::HighlightScrolledLines));
+
     // margin/center
     setMargin(profile->property<int>(Profile::TerminalMargin));
     setCenterContents(profile->property<bool>(Profile::TerminalCenter));

src/TerminalDisplay.h

@@ -117,6 +117,8 @@ public:
 
     void setScrollFullPage(bool fullPage);
     bool scrollFullPage() const;
+    void setHighlightScrolledLines(bool highlight);
+
     /**
      * Returns the display's filter chain.  When the image for the display is updated,
      * the text is passed through each filter in the chain.  Each filter can define
@@ -614,6 +616,7 @@ protected Q_SLOTS:
     void scrollBarPositionChanged(int value);
     void blinkTextEvent();
     void blinkCursorEvent();
+    void highlightScrolledLinesEvent();
 
 private Q_SLOTS:
 
@@ -634,6 +637,11 @@ private:
     void drawContents(QPainter &painter, const QRect &rect);
     // draw a transparent rectangle over the line of the current match
     void drawCurrentResultRect(QPainter &painter);
+    // draw a thin highlight on the left of the screen for lines that have been scrolled into view
+    void highlightScrolledLines(QPainter& painter);
+    // compute which region need to be repainted for scrolled lines highlight
+    QRect highlightScrolledLinesRegion(void);
+
     // draws a section of text, all the text in this section
     // has a common color and style
     void drawTextFragment(QPainter &painter, const QRect &rect, const QString &text,
@@ -891,6 +899,14 @@ private:
     bool _drawOverlay;
     Qt::Edge _overlayEdge;
 
+    struct {
+        bool enabled = false;
+        QRect rect;
+        int previousScrollCount = 0;
+        QTimer *timer = nullptr;
+    } _highlightScrolledLinesControl;
+    static const int HIGHLIGHT_SCROLLED_LINES_WIDTH = 3;
+
     bool _hasCompositeFocus;
 
     QSharedPointer<Filter::HotSpot> _currentlyHoveredHotspot;