OffsetX and OffsetY introduced

buffer.go

@@ -7,6 +7,7 @@ import (
 // Buffer is a 2-dimensional buffer
 type Buffer[T any] struct {
 	data       [][]T
+	x, y       int
 	width      int
 	height     int
 	parent     *Buffer[T]
@@ -24,6 +25,7 @@ func NewBuffer[T any](width, height int, defaultValue T) *Buffer[T] {
 	}
 
 	return &Buffer[T]{
+		x: 0, y: 0,
 		data:       b,
 		width:      width,
 		height:     height,
@@ -32,18 +34,18 @@ func NewBuffer[T any](width, height int, defaultValue T) *Buffer[T] {
 	}
 }
 
-func (b *Buffer[T]) x(x int) int {
+func (b *Buffer[T]) limX(x int) int {
 	return limit(x, 0, b.width-1)
 }
 
-func (b *Buffer[T]) y(y int) int {
+func (b *Buffer[T]) limY(y int) int {
 	return limit(y, 0, b.height-1)
 }
 
 // Set sets the value at position (x,y) to c
 func (b *Buffer[T]) Set(x, y int, v T) {
 	if b.width > 0 && b.height > 0 {
-		b.data[b.y(y)][b.x(x)] = v
+		b.data[b.limY(y)][b.limX(x)] = v
 	}
 }
 
@@ -67,14 +69,26 @@ func (b *Buffer[T]) Height() int {
 	return b.height
 }
 
-// ForEach calls f for every value in this buffer
+// OffsetX returns the horizontal offset of b relative to its parent buffer.
+// OffsetX returns 0 if b has no parent
+func (b *Buffer[T]) OffsetX() int {
+	return b.x
+}
+
+// OffsetY returns the vertical offset of b relative to its parent buffer.
+// OffsetY returns 0 if b has no parent
+func (b *Buffer[T]) OffsetY() int {
+	return b.y
+}
+
+// ForEachLine calls f for each line in b
 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
+// ForEach calls f for every value in b
 func (b *Buffer[T]) ForEach(f func(x, y int, v T)) {
 	for y, col := range b.data {
 		for x, v := range col {
@@ -116,6 +130,7 @@ func (b *Buffer[T]) Sub(x, y, w, h int) *Buffer[T] {
 
 	// make buffer
 	return &Buffer[T]{
+		x: x, y: y,
 		data:       data,
 		width:      w,
 		height:     h,

buffer_test.go

@@ -22,3 +22,9 @@ func TestSet(t *testing.T) {
 	b := NewBuffer(0, 0, ' ')
 	b.Set(0, 0, 'a')
 }
+
+func TestOffset(t *testing.T) {
+	b := NewBuffer(10, 10, ' ')
+	b = b.Sub(3, 3, 3, 3)
+	fmt.Println(b.OffsetX(), b.OffsetY())
+}