Refactor RequiredWidth off the Y object.

widgets/linechart/axes/axes.go

@@ -76,14 +76,15 @@ func (y *Y) Update(minVal, maxVal float64) {
 }
 
 // RequiredWidth calculates the minimum width required in order to draw the Y
-// axis and its labels.
-func (y *Y) RequiredWidth() int {
+// axis and its labels when displaying values that have this minimum and
+// maximum among all the series.
+func RequiredWidth(minVal, maxVal float64) int {
 	// This is an estimation only, it is possible that more labels in the
 	// middle will be generated and might be wider than this. Such cases are
 	// handled on the call to Details when the size of canvas is known.
 	return longestLabel([]*Label{
-		{Value: y.min},
-		{Value: y.max},
+		{Value: NewValue(minVal, nonZeroDecimals)},
+		{Value: NewValue(maxVal, nonZeroDecimals)},
 	}) + axisWidth
 }
 
@@ -94,7 +95,7 @@ func (y *Y) Details(cvsAr image.Rectangle, reqXHeight int, mode YScaleMode) (*YD
 	cvsWidth := cvsAr.Dx()
 	cvsHeight := cvsAr.Dy()
 	maxWidth := cvsWidth - 1 // Reserve one column for the line chart itself.
-	if req := y.RequiredWidth(); maxWidth < req {
+	if req := RequiredWidth(y.min.Value, y.max.Value); maxWidth < req {
 		return nil, fmt.Errorf("the available maxWidth %d is smaller than the reported required width %d", maxWidth, req)
 	}
 

widgets/linechart/axes/axes_test.go

@@ -186,7 +186,7 @@ func TestY(t *testing.T) {
 				y.Update(tc.update.minVal, tc.update.maxVal)
 			}
 
-			gotWidth := y.RequiredWidth()
+			gotWidth := RequiredWidth(tc.minVal, tc.maxVal)
 			if gotWidth != tc.wantWidth {
 				t.Errorf("RequiredWidth => got %v, want %v", gotWidth, tc.wantWidth)
 			}

widgets/linechart/linechart.go

@@ -81,6 +81,8 @@ type LineChart struct {
 
 	// yAxis is the Y axis of the line chart.
 	yAxis *axes.Y
+	// yMin are the min and max values for the Y axis.
+	yMin, yMax float64
 
 	// opts are the provided options.
 	opts *options
@@ -188,7 +190,10 @@ func (lc *LineChart) Series(label string, values []float64, opts ...SeriesOption
 	}
 
 	lc.series[label] = series
-	lc.yAxis = axes.NewY(lc.yMinMax())
+	yMin, yMax := lc.yMinMax()
+	lc.yAxis = axes.NewY(yMin, yMax)
+	lc.yMin = yMin
+	lc.yMax = yMax
 	return nil
 }
 
@@ -335,7 +340,7 @@ func (lc *LineChart) minSize() image.Point {
 	// At the very least we need:
 	// - n cells width for the Y axis and its labels as reported by it.
 	// - at least 1 cell width for the graph.
-	reqWidth := lc.yAxis.RequiredWidth() + 1
+	reqWidth := axes.RequiredWidth(lc.yMin, lc.yMax) + 1
 
 	// And for the height:
 	// - n cells width for the X axis and its labels as reported by it.