ComboTabBar: Add support for drawing drop indicator

It's just a solid line now, should be improved later.

src/lib/tabwidget/combotabbar.cpp

@@ -799,6 +799,17 @@ void ComboTabBar::setUsesScrollButtons(bool useButtons)
     m_mainTabBarWidget->setUsesScrollButtons(useButtons);
 }
 
+void ComboTabBar::showDropIndicator(int index, DropIndicatorPosition position)
+{
+    localTabBar(index)->showDropIndicator(toLocalIndex(index), position);
+}
+
+void ComboTabBar::clearDropIndicator()
+{
+    m_mainTabBar->clearDropIndicator();
+    m_pinnedTabBar->clearDropIndicator();
+}
+
 bool ComboTabBar::isDragInProgress() const
 {
     return m_mainTabBar->isDragInProgress() || m_pinnedTabBar->isDragInProgress();
@@ -1041,6 +1052,19 @@ void TabBarHelper::useFastTabSizeHint(bool enabled)
     m_useFastTabSizeHint = enabled;
 }
 
+void TabBarHelper::showDropIndicator(int index, ComboTabBar::DropIndicatorPosition position)
+{
+    m_dropIndicatorIndex = index;
+    m_dropIndicatorPosition = position;
+    update();
+}
+
+void TabBarHelper::clearDropIndicator()
+{
+    m_dropIndicatorIndex = -1;
+    update();
+}
+
 bool TabBarHelper::isDisplayedOnViewPort(int globalLeft, int globalRight)
 {
     bool isVisible = true;
@@ -1209,6 +1233,18 @@ void TabBarHelper::paintEvent(QPaintEvent* event)
 
         p.drawControl(QStyle::CE_TabBarTab, tab);
     }
+
+    // Draw drop indicator
+    if (m_dropIndicatorIndex != -1) {
+        p.setPen(QPen(palette().text(), 3));
+        QRect r = tabRect(m_dropIndicatorIndex);
+        if (m_dropIndicatorPosition == ComboTabBar::BeforeTab) {
+            r.moveLeft(r.x() - 1);
+            p.drawLine(r.topLeft(), r.bottomLeft());
+        } else {
+            p.drawLine(r.topRight(), r.bottomRight());
+        }
+    }
 }
 
 void TabBarHelper::mousePressEvent(QMouseEvent* event)

src/lib/tabwidget/combotabbar.h

@@ -52,6 +52,11 @@ public:
         ExtraReservedWidth
     };
 
+    enum DropIndicatorPosition {
+        BeforeTab,
+        AfterTab
+    };
+
     explicit ComboTabBar(QWidget* parent = 0);
 
     int addTab(const QString &text);
@@ -136,6 +141,9 @@ public:
     bool usesScrollButtons() const;
     void setUsesScrollButtons(bool useButtons);
 
+    void showDropIndicator(int index, DropIndicatorPosition position);
+    void clearDropIndicator();
+
     bool isDragInProgress() const;
     bool isScrollInProgress() const;
     bool isMainBarOverflowed() const;
@@ -234,6 +242,9 @@ public:
     void setScrollArea(QScrollArea* scrollArea);
     void useFastTabSizeHint(bool enabled);
 
+    void showDropIndicator(int index, ComboTabBar::DropIndicatorPosition position);
+    void clearDropIndicator();
+
     bool isDisplayedOnViewPort(int globalLeft, int globalRight);
     bool isDragInProgress() const;
 
@@ -266,6 +277,8 @@ private:
     bool m_activeTabBar;
     bool m_isPinnedTabBar;
     bool m_useFastTabSizeHint;
+    int m_dropIndicatorIndex = -1;
+    ComboTabBar::DropIndicatorPosition m_dropIndicatorPosition;
 };
 
 class FALKON_EXPORT TabScrollBar : public QScrollBar