Remove spacers in non-LargeSideBar modes for FancyTabWidget

To maintain behavior with the older FancyTabWidget, spacers are now
removed and stored when switching to a non-LargeSideBar mode.
And subsequently restored when switching back to LargeSideBar mode.

src/widgets/fancytabwidget.cpp

@@ -31,6 +31,7 @@
 #include <QTimer>
 #include <QVBoxLayout>
 #include <QSettings>
+#include <QMap>
 
 const QSize FancyTabWidget::IconSize_LargeSidebar = QSize(24,24);
 const QSize FancyTabWidget::IconSize_SmallSidebar = QSize(22,22);
@@ -42,6 +43,7 @@ class FancyTabBar: public QTabBar {
 private:
     int mouseHoverTabIndex = -1;
     QMap<QWidget*,QString> labelCache;
+    QMap<int, QWidget*> spacers;
 
 public:
     explicit FancyTabBar(QWidget* parent=0) : QTabBar(parent) {
@@ -102,6 +104,26 @@ class FancyTabBar: public QTabBar {
         if(tabWidget->mode() == FancyTabWidget::Mode_SmallSidebar)
             verticalTextTabs = true;
 
+        // if LargeSidebar, restore spacers
+        if (spacers.count() > 0 && tabWidget->mode() == FancyTabWidget::Mode_LargeSidebar) {
+            for (int index : spacers.keys()) {
+                tabWidget->insertTab(index, spacers[index], QIcon(), QString());
+                tabWidget->setTabEnabled(index, false);
+            }
+            spacers.clear();
+        }
+        if (tabWidget->mode() != FancyTabWidget::Mode_LargeSidebar) {
+            // traverse in the opposite order to save indices of spacers
+            for (int i = count() - 1; i >= 0; --i) {
+                // spacers are disabled tabs
+                if (!isTabEnabled(i) && !spacers.contains(i)) {
+                    spacers[i] = tabWidget->widget(i);
+                    tabWidget->removeTab(i);
+                    --i;
+                }
+            }
+        }
+
         // Restore any label text that was hidden/cached for the IconOnlyTabs mode
         if(labelCache.count() > 0 && tabWidget->mode() != FancyTabWidget::Mode_IconOnlyTabs) {
                 for(int i =0; i < count(); i++) {