fixed panic when writing to zero-sized buffer

buffer.go

@@ -42,7 +42,9 @@ func (b *Buffer[T]) y(y int) int {
 
 // Set sets the value at position (x,y) to c
 func (b *Buffer[T]) Set(x, y int, v T) {
-	b.data[b.y(y)][b.x(x)] = v
+	if b.width >= 0 && b.height >= 0 {
+		b.data[b.y(y)][b.x(x)] = v
+	}
 }
 
 // Get returns the value at position (x,y)
@@ -65,6 +67,13 @@ func (b *Buffer[T]) Height() int {
 	return b.height
 }
 
+// ForEach calls f for every value in this buffer
+func (b *Buffer[T]) ForEachLine(f func(line int, content []T)) {
+	for line, content := range b.data {
+		f(line, content)
+	}
+}
+
 // ForEach calls f for every value in this buffer
 func (b *Buffer[T]) ForEach(f func(x, y int, v T)) {
 	for y, col := range b.data {
@@ -95,8 +104,8 @@ func (b *Buffer[T]) Sub(x, y, w, h int) *Buffer[T] {
 	// sanitize inputs
 	x = limit(x, 0, b.width-1)
 	y = limit(y, 0, b.height-1)
-	w = limit(w, 1, b.width-x)
-	h = limit(h, 1, b.height-y)
+	w = limit(w, 0, b.width-x)
+	h = limit(h, 0, b.height-y)
 
 	// make slice references
 	data := make([][]T, h)

buffer_test.go

@@ -17,3 +17,8 @@ func TestSub(t *testing.T) {
 	fmt.Println(strings.Repeat("-", 10))
 	fmt.Println(s)
 }
+
+func TestSet(t *testing.T) {
+	b := NewBuffer(10, 10, ' ')
+	b.Set(11, 0, 'a')
+}