add compact flag

Add an option to render the list compactly (without blank lines between `ListItem`s). This flag will be ignored if `showSecondaryText` is set to true.

list.go

@@ -194,6 +194,10 @@ type List struct {
 	// The height of the list the last time it was drawn.
 	height int
 
+	// If true, will render each ListItem without blank lines in between. This flag 
+	// is ignored if `showSecondaryText` is true.
+	compact bool
+
 	sync.RWMutex
 }
 
@@ -209,6 +213,7 @@ func NewList() *List {
 		selectedTextColor:       Styles.PrimitiveBackgroundColor,
 		scrollBarColor:          Styles.ScrollBarColor,
 		selectedBackgroundColor: Styles.PrimaryTextColor,
+		compact:				 false,
 	}
 
 	l.ContextMenu = NewContextMenu(l)
@@ -519,6 +524,15 @@ func (l *List) SetDoneFunc(handler func()) {
 	l.done = handler
 }
 
+// SetCompactList sets the flag that determines whether a blank line is drawn between 
+// each ListItem. This flag will be ignored if `showSecondaryText` is true. 
+func (l *List) SetCompactList(compact bool) {
+	l.Lock()
+	defer l.Unlock()
+
+	l.compact = compact
+}
+
 // AddItem calls InsertItem() with an index of -1.
 func (l *List) AddItem(item *ListItem) {
 	l.InsertItem(-1, item)
@@ -799,7 +813,11 @@ func (l *List) updateOffset() {
 		}
 	} else {
 		if l.currentItem-l.itemOffset >= h {
-			l.itemOffset = l.currentItem + 1 - h
+			if l.compact {
+				l.itemOffset = l.currentItem - h
+			} else {
+				l.itemOffset = l.currentItem + 1 - h
+			}
 		}
 	}
 
@@ -978,7 +996,10 @@ func (l *List) Draw(screen tcell.Screen) {
 
 		RenderScrollBar(screen, l.scrollBarVisibility, scrollBarX, y, scrollBarHeight, len(l.items), scrollBarCursor, index-l.itemOffset, l.hasFocus, l.scrollBarColor)
 
-		y++
+		// Compact List
+		if !l.compact {
+			y++
+		}
 
 		if y >= bottomLimit {
 			break