Add logic for focusing

box.go

@@ -294,6 +294,14 @@ func (this *box) boxUnder (point image.Point) anyBox {
 	}
 }
 
+func (this *box) handleFocusEnter () {
+	this.on.focusEnter.Broadcast()
+}
+
+func (this *box) handleFocusLeave () {
+	this.on.focusLeave.Broadcast()
+}
+
 func (this *box) handleMouseDown (button input.Button) {
 	for _, listener := range this.on.mouseDown.Listeners() {
 		listener(button)

system.go

@@ -48,8 +48,19 @@ type anyBox interface {
 	boxUnder      (image.Point) anyBox
 	recalculateMinimumSize ()
 
-	handleMouseDown (input.Button)
-	handleMouseUp   (input.Button)
+	handleFocusEnter ()
+	handleFocusLeave ()
+	// handleDndEnter   ()
+	// handleDndLeave   ()
+	// handleDndDrop    (data.Data)
+	// handleMouseEnter ()
+	// handleMouseLeave ()
+	// handleMouseMove  ()
+	handleMouseDown  (input.Button)
+	handleMouseUp    (input.Button)
+	// handleScroll     (float64, float64)
+	// handleKeyDown    (input.Key, bool)
+	// handleKeyUp      (input.Key, bool)
 }
 
 func assertAnyBox (unknown tomo.Box) anyBox {
@@ -100,9 +111,18 @@ func (window *window) invalidateLayout (box anyBox) {
 
 func (window *window) focus (box anyBox) {
 	if window.focused == box { return }
-	window.invalidateDraw(window.focused)
+	
+	previous := window.focused
 	window.focused = box
-	window.invalidateDraw(box)
+	
+	if previous != nil {
+		window.invalidateDraw(previous)
+		previous.handleFocusLeave()
+	}
+	if box != nil {
+		window.invalidateDraw(box)
+		box.handleFocusEnter()
+	}
 }
 
 func (this *window) boxUnder (point image.Point) anyBox {

textbox.go

@@ -149,14 +149,6 @@ func (this *textBox) doLayout () {
 	innerBounds := this.InnerBounds()
 	this.drawer.SetMaxWidth(innerBounds.Dx())
 	this.drawer.SetMaxHeight(innerBounds.Dy())
-	// if this.hOverflow && !this.wrap {
-		// this.drawer.SetMaxWidth(0)
-	// } else {
-	// }
-	// if this.vOverflow {
-		// this.drawer.SetMaxHeight(0)
-	// } else {
-	// }
 	
 	this.contentBounds = this.normalizedLayoutBoundsSpace().Sub(this.scroll)