4 files changed, 37 insertions, 32 deletions
diff --git a/lib/ui/borders.go b/lib/ui/borders.go
index 9b7860e..cffd3ca 100644
--- a/lib/ui/borders.go
+++ b/lib/ui/borders.go
@@ -12,6 +12,7 @@ const (
 )
 
 type Bordered struct {
+	Invalidatable
 	borders      uint
 	content      Drawable
 	onInvalidate func(d Drawable)
@@ -35,13 +36,7 @@ func (bordered *Bordered) Children() []Drawable {
 }
 
 func (bordered *Bordered) Invalidate() {
-	if bordered.onInvalidate != nil {
-		bordered.onInvalidate(bordered)
-	}
-}
-
-func (bordered *Bordered) OnInvalidate(onInvalidate func(d Drawable)) {
-	bordered.onInvalidate = onInvalidate
+	bordered.DoInvalidate(bordered)
 }
 
 func (bordered *Bordered) Draw(ctx *Context) {
diff --git a/lib/ui/grid.go b/lib/ui/grid.go
index 87b94bd..3ac43a4 100644
--- a/lib/ui/grid.go
+++ b/lib/ui/grid.go
@@ -6,12 +6,12 @@ import (
 )
 
 type Grid struct {
+	Invalidatable
 	rows         []GridSpec
 	rowLayout    []gridLayout
 	columns      []GridSpec
 	columnLayout []gridLayout
 	cells        []*GridCell
-	onInvalidate func(d Drawable)
 	invalid      bool
 }
 
@@ -141,9 +141,7 @@ func (grid *Grid) reflow(ctx *Context) {
 
 func (grid *Grid) invalidateLayout() {
 	grid.invalid = true
-	if grid.onInvalidate != nil {
-		grid.onInvalidate(grid)
-	}
+	grid.DoInvalidate(grid)
 }
 
 func (grid *Grid) Invalidate() {
@@ -153,10 +151,6 @@ func (grid *Grid) Invalidate() {
 	}
 }
 
-func (grid *Grid) OnInvalidate(onInvalidate func(d Drawable)) {
-	grid.onInvalidate = onInvalidate
-}
-
 func (grid *Grid) AddChild(content Drawable) *GridCell {
 	cell := &GridCell{
 		RowSpan: 1,
@@ -193,7 +187,5 @@ func (grid *Grid) cellInvalidated(drawable Drawable) {
 		panic(fmt.Errorf("Attempted to invalidate unknown cell"))
 	}
 	cell.invalid = true
-	if grid.onInvalidate != nil {
-		grid.onInvalidate(grid)
-	}
+	grid.DoInvalidate(grid)
 }
diff --git a/lib/ui/invalidatable.go b/lib/ui/invalidatable.go
new file mode 100644
index 0000000..9275712
--- /dev/null
+++ b/lib/ui/invalidatable.go
@@ -0,0 +1,24 @@
+package ui
+
+import (
+	"sync/atomic"
+)
+
+type Invalidatable struct {
+	onInvalidate atomic.Value
+}
+
+func (i *Invalidatable) OnInvalidate(f func(d Drawable)) {
+	i.onInvalidate.Store(f)
+}
+
+func (i *Invalidatable) DoInvalidate(d Drawable) {
+	v := i.onInvalidate.Load()
+	if v == nil {
+		return
+	}
+	f := v.(func(d Drawable))
+	if f != nil {
+		f(d)
+	}
+}
diff --git a/lib/ui/text.go b/lib/ui/text.go
index 761673c..8aea8eb 100644
--- a/lib/ui/text.go
+++ b/lib/ui/text.go
@@ -12,13 +12,13 @@ const (
 )
 
 type Text struct {
-	text         string
-	strategy     uint
-	fg           tcell.Color
-	bg           tcell.Color
-	bold         bool
-	reverse      bool
-	onInvalidate func(d Drawable)
+	Invalidatable
+	text     string
+	strategy uint
+	fg       tcell.Color
+	bg       tcell.Color
+	bold     bool
+	reverse  bool
 }
 
 func NewText(text string) *Text {
@@ -80,12 +80,6 @@ func (t *Text) Draw(ctx *Context) {
 	ctx.Printf(x, 0, style, t.text)
 }
 
-func (t *Text) OnInvalidate(onInvalidate func(d Drawable)) {
-	t.onInvalidate = onInvalidate
-}
-
 func (t *Text) Invalidate() {
-	if t.onInvalidate != nil {
-		t.onInvalidate(t)
-	}
+	t.DoInvalidate(t)
 }