Fix #23 by implementing Block.InnerBounds() and associated test.

block.go

@@ -68,6 +68,13 @@ func (d *Block) align() {
 
 }
 
+// InnerBounds returns the internal bounds of the block after aligning and
+// calculating the padding and border, if any.
+func (d *Block) InnerBounds() (x, y, width, height int) {
+	d.align()
+	return d.innerX, d.innerY, d.innerWidth, d.innerHeight
+}
+
 // Buffer implements Bufferer interface.
 // Draw background and border (if any).
 func (d *Block) Buffer() []Point {

block_test.go

@@ -0,0 +1,46 @@
+package termui
+
+import "testing"
+
+func TestBlock_InnerBounds(t *testing.T) {
+	b := NewBlock()
+	b.X = 10
+	b.Y = 11
+	b.Width = 12
+	b.Height = 13
+
+	assert := func(name string, x, y, w, h int) {
+		t.Log(name)
+		cx, cy, cw, ch := b.InnerBounds()
+		if cx != x {
+			t.Errorf("expected x to be %d but got %d", x, cx)
+		}
+		if cy != y {
+			t.Errorf("expected y to be %d but got %d", y, cy)
+		}
+		if cw != w {
+			t.Errorf("expected width to be %d but got %d", w, cw)
+		}
+		if ch != h {
+			t.Errorf("expected height to be %d but got %d", h, ch)
+		}
+	}
+
+	b.HasBorder = false
+	assert("no border, no padding", 10, 11, 12, 13)
+
+	b.HasBorder = true
+	assert("border, no padding", 11, 12, 10, 11)
+
+	b.PaddingBottom = 2
+	assert("border, 2b padding", 11, 12, 10, 9)
+
+	b.PaddingTop = 3
+	assert("border, 2b 3t padding", 11, 15, 10, 6)
+
+	b.PaddingLeft = 4
+	assert("border, 2b 3t 4l padding", 15, 15, 6, 6)
+
+	b.PaddingRight = 5
+	assert("border, 2b 3t 4l 5r padding", 15, 15, 1, 6)
+}