Add NotifyAt (#5)

grid.go

@@ -130,6 +130,14 @@ func (m *Grid) MergeAt(x, y int16, tile, mask Tile) {
 	}
 }
 
+// NotifyAt triggers the notification event for all of the observers at a given tile.
+func (m *Grid) NotifyAt(x, y int16) {
+	if x >= 0 && y >= 0 && x < m.Size.X && y < m.Size.Y {
+		tile := m.pages[m.indexOf(x/3, y/3)].Get(x, y)
+		m.observers.Notify(At(x/3*3, y/3*3), At(x, y), tile)
+	}
+}
+
 // Neighbors iterates over the direct neighbouring tiles
 func (m *Grid) Neighbors(x, y int16, fn Iterator) {
 
@@ -166,7 +174,7 @@ func (m *Grid) Neighbors(x, y int16, fn Iterator) {
 func (m *Grid) View(rect Rect, fn Iterator) *View {
 	view := &View{
 		Grid:  m,
-		Inbox: make(chan Update, 8),
+		Inbox: make(chan Update, 16),
 		rect:  NewRect(-1, -1, -1, -1),
 	}
 

view_test.go

@@ -10,18 +10,25 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-// BenchmarkView/write-8         	11170822	       105.1 ns/op	      16 B/op	       1 allocs/op
-// BenchmarkView/move-8          	    9049	    163019 ns/op	       0 B/op	       0 allocs/op
+/*
+cpu: Intel(R) Core(TM) i7-9700K CPU @ 3.60GHz
+BenchmarkView/write-8         	 5910660	       191.7 ns/op	      16 B/op	       1 allocs/op
+BenchmarkView/move-8          	    8253	    138149 ns/op	       0 B/op	       0 allocs/op
+BenchmarkView/notify-8        	 6024670	       197.5 ns/op	      16 B/op	       1 allocs/op
+*/
 func BenchmarkView(b *testing.B) {
 	m := mapFrom("300x300.png")
 	v := m.View(NewRect(100, 0, 199, 99), nil)
+	go func() {
+		for range v.Inbox {
+		}
+	}()
 
 	b.Run("write", func(b *testing.B) {
 		b.ReportAllocs()
 		b.ResetTimer()
 		for n := 0; n < b.N; n++ {
 			v.WriteAt(152, 52, Tile{})
-			<-v.Inbox
 		}
 	})
 
@@ -37,6 +44,14 @@ func BenchmarkView(b *testing.B) {
 			v.MoveAt(locs[n%2], nil)
 		}
 	})
+
+	b.Run("notify", func(b *testing.B) {
+		b.ReportAllocs()
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			m.NotifyAt(150, 50)
+		}
+	})
 }
 
 func TestView(t *testing.T) {
@@ -133,6 +148,21 @@ func TestObserversNil(t *testing.T) {
 	})
 }
 
+func TestNotifyAt(t *testing.T) {
+	m := mapFrom("300x300.png")
+
+	// Create a new view
+	c := counter(0)
+	v := m.View(NewRect(0, 0, 99, 99), c.count)
+	assert.NotNil(t, v)
+	assert.Equal(t, 10000, int(c))
+
+	m.NotifyAt(1, 1)
+	update := <-v.Inbox
+	assert.Equal(t, int16(1), update.X)
+	assert.Equal(t, int16(1), update.Y)
+}
+
 type fakeView func(*Update)
 
 func (f fakeView) onUpdate(e *Update) {