Fix https://github.com/gizak/termui/issues/18

Add Block.chopOverflow and apply it to all widgets

bar.go

@@ -120,5 +120,5 @@ func (bc *BarChart) Buffer() []Point {
 		}
 	}
 
-	return ps
+	return bc.Block.chopOverflow(ps)
 }

block.go

@@ -122,3 +122,21 @@ func (d *Block) SetY(y int) {
 func (d *Block) SetWidth(w int) {
 	d.Width = w
 }
+
+// chop the overflow parts
+func (d *Block) chopOverflow(ps []Point) []Point {
+	nps := make([]Point, 0, len(ps))
+	x := d.X
+	y := d.Y
+	w := d.Width
+	h := d.Height
+	for _, v := range ps {
+		if v.X >= x &&
+			v.X < x+w &&
+			v.Y >= y &&
+			v.Y < y+h {
+			nps = append(nps, v)
+		}
+	}
+	return nps
+}

chart.go

@@ -327,5 +327,5 @@ func (lc *LineChart) Buffer() []Point {
 		ps = append(ps, lc.renderBraille()...)
 	}
 
-	return ps
+	return lc.Block.chopOverflow(ps)
 }

gauge.go

@@ -79,5 +79,5 @@ func (g *Gauge) Buffer() []Point {
 		}
 		ps = append(ps, p)
 	}
-	return ps
+	return g.Block.chopOverflow(ps)
 }

list.go

@@ -100,5 +100,5 @@ func (l *List) Buffer() []Point {
 			}
 		}
 	}
-	return ps
+	return l.Block.chopOverflow(ps)
 }

p.go

@@ -67,5 +67,5 @@ func (p *Par) Buffer() []Point {
 		k++
 		j += w
 	}
-	return ps
+	return p.Block.chopOverflow(ps)
 }

sparkline.go

@@ -152,5 +152,5 @@ func (sl *Sparklines) Buffer() []Point {
 		oftY += l.displayHeight
 	}
 
-	return ps
+	return sl.Block.chopOverflow(ps)
 }