Update README

CHANGELOG

@@ -1,4 +1,4 @@
-v1.4.4 (WIP)
+v1.4.4 (2020-02-24)
 - Fix panic when navigating empty list
 - Fix resize event dimensions on Windows
 - Clarify that Box does not have inner text

README.md

@@ -67,6 +67,9 @@ the program in the "demos/presentation" subdirectory.
 
 Package documentation is available via [godoc](https://docs.rocketnine.space/gitlab.com/tslocum/cview).
 
+**This package is not thread-safe.** Most functions may only be called from the
+main thread, as documented in [Concurrency](https://docs.rocketnine.space/gitlab.com/tslocum/cview/#hdr-Concurrency).
+
 An [introduction tutorial](https://rocketnine.space/post/tview-and-you/) is also available.
 
 ## Dependencies

application.go

@@ -757,7 +757,7 @@ func (a *Application) QueueEvent(event tcell.Event) *Application {
 
 // RingBell sends a bell code to the terminal.
 func (a *Application) RingBell() {
-	a.Lock()
-	fmt.Print(string(byte(7)))
-	a.Unlock()
+	a.QueueUpdate(func() {
+		fmt.Print(string(byte(7)))
+	})
 }

list.go

@@ -509,6 +509,7 @@ func (l *List) Draw(screen tcell.Screen) {
 	// Overdraw scroll bar when necessary.
 	for y < bottomLimit {
 		RenderScrollBar(screen, l.scrollBarVisibility, scrollBarX, y, scrollBarHeight, len(l.items), l.currentItem, bottomLimit-y, l.hasFocus, l.scrollBarColor)
+
 		y++
 	}
 }