Add List.Transform

CHANGELOG

@@ -1,7 +1,7 @@
 v1.4.5 (WIP)
 - Add multithreading support
 - Add ContextMenu (initially supported by List)
-- Add TreeView.Transform
+- Add List.Transform and TreeView.Transform
 - Merge upstream mouse support
 
 v1.4.4 (2020-02-24)

list.go

@@ -537,6 +537,63 @@ func (l *List) HasFocus() bool {
 	return l.hasFocus
 }
 
+// Transform modifies the current selection.
+func (l *List) Transform(tr Transformation) {
+	l.Lock()
+	defer l.Unlock()
+
+	l.transform(tr)
+}
+
+func (l *List) transform(tr Transformation) {
+	var decreasing bool
+
+	switch tr {
+	case TransformFirstItem:
+		l.currentItem = 0
+		decreasing = true
+	case TransformLastItem:
+		l.currentItem = len(l.items) - 1
+	case TransformPreviousItem:
+		l.currentItem -= 1
+		decreasing = true
+	case TransformNextItem:
+		l.currentItem += 1
+	case TransformPreviousPage:
+		l.currentItem -= 5
+		decreasing = true
+	case TransformNextPage:
+		l.currentItem += 5
+	}
+
+	for i := 0; i < len(l.items); i++ {
+		if l.currentItem < 0 {
+			if l.wrapAround {
+				l.currentItem = len(l.items) - 1
+			} else {
+				l.currentItem = 0
+			}
+		} else if l.currentItem >= len(l.items) {
+			if l.wrapAround {
+				l.currentItem = 0
+			} else {
+				l.currentItem = len(l.items) - 1
+			}
+		}
+
+		item := l.items[l.currentItem]
+		if item.Enabled {
+			break
+		}
+
+		if decreasing {
+			l.currentItem--
+		} else {
+			l.currentItem++
+		}
+	}
+}
+
 // Draw draws this primitive onto the screen.
 func (l *List) Draw(screen tcell.Screen) {
 	l.Box.Draw(screen)
@@ -750,18 +807,18 @@ func (l *List) InputHandler() func(event *tcell.EventKey, setFocus func(p Primit
 		previousItem := l.currentItem
 
 		switch key := event.Key(); key {
-		case tcell.KeyTab, tcell.KeyDown, tcell.KeyRight:
-			l.currentItem++
-		case tcell.KeyBacktab, tcell.KeyUp, tcell.KeyLeft:
-			l.currentItem--
 		case tcell.KeyHome:
-			l.currentItem = 0
+			l.transform(TransformFirstItem)
 		case tcell.KeyEnd:
-			l.currentItem = len(l.items) - 1
-		case tcell.KeyPgDn:
-			l.currentItem += 5
+			l.transform(TransformLastItem)
+		case tcell.KeyBacktab, tcell.KeyUp, tcell.KeyLeft:
+			l.transform(TransformPreviousItem)
+		case tcell.KeyTab, tcell.KeyDown, tcell.KeyRight:
+			l.transform(TransformNextItem)
 		case tcell.KeyPgUp:
-			l.currentItem -= 5
+			l.transform(TransformPreviousPage)
+		case tcell.KeyPgDn:
+			l.transform(TransformNextPage)
 		case tcell.KeyEnter:
 			if event.Modifiers()&tcell.ModAlt != 0 {
 				// Do we show any shortcuts?
@@ -829,34 +886,6 @@ func (l *List) InputHandler() func(event *tcell.EventKey, setFocus func(p Primit
 			}
 		}
 
-		decreasing := l.currentItem < previousItem
-		for i := 0; i < len(l.items); i++ {
-			if l.currentItem < 0 {
-				if l.wrapAround {
-					l.currentItem = len(l.items) - 1
-				} else {
-					l.currentItem = 0
-				}
-			} else if l.currentItem >= len(l.items) {
-				if l.wrapAround {
-					l.currentItem = 0
-				} else {
-					l.currentItem = len(l.items) - 1
-				}
-			}
-
-			item := l.items[l.currentItem]
-			if item.Enabled {
-				break
-			}
-
-			if decreasing {
-				l.currentItem--
-			} else {
-				l.currentItem++
-			}
-		}
-
 		if l.currentItem != previousItem && l.currentItem < len(l.items) && l.changed != nil {
 			item := l.items[l.currentItem]
 			l.Unlock()