potential fix for issue with large deltas rounding the y axis

_examples/scatter/main.go

@@ -16,26 +16,8 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 					StrokeWidth: chart.Disabled,
 					DotWidth:    3,
 				},
-				XValues: chart.Sequence.Random(32, 1024),
-				YValues: chart.Sequence.Random(32, 1024),
-			},
-			chart.ContinuousSeries{
-				Style: chart.Style{
-					Show:        true,
-					StrokeWidth: chart.Disabled,
-					DotWidth:    5,
-				},
-				XValues: chart.Sequence.Random(16, 1024),
-				YValues: chart.Sequence.Random(16, 1024),
-			},
-			chart.ContinuousSeries{
-				Style: chart.Style{
-					Show:        true,
-					StrokeWidth: chart.Disabled,
-					DotWidth:    7,
-				},
-				XValues: chart.Sequence.Random(8, 1024),
-				YValues: chart.Sequence.Random(8, 1024),
+				XValues: chart.Sequence.Random(4096, 1024),
+				YValues: chart.Sequence.Random(4096, 1024),
 			},
 		},
 	}

chart.go

@@ -98,11 +98,11 @@ func (c Chart) Render(rp RendererProvider, w io.Writer) error {
 	xr, yr, yra := c.getRanges()
 	canvasBox := c.getDefaultCanvasBox()
 	xf, yf, yfa := c.getValueFormatters()
+
 	xr, yr, yra = c.setRangeDomains(canvasBox, xr, yr, yra)
 
 	err = c.checkRanges(xr, yr, yra)
 	if err != nil {
-		// (try to) dump the raw background to the stream.
 		r.Save(w)
 		return err
 	}
@@ -260,12 +260,16 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 		yrange.SetMin(miny)
 		yrange.SetMax(maxy)
 
+		// only round if we're showing the axis
+		if c.YAxis.Style.Show {
 			delta := yrange.GetDelta()
 			roundTo := Math.GetRoundToForDelta(delta)
 			rmin, rmax := Math.RoundDown(yrange.GetMin(), roundTo), Math.RoundUp(yrange.GetMax(), roundTo)
+
 			yrange.SetMin(rmin)
 			yrange.SetMax(rmax)
 		}
+	}
 
 	if len(c.YAxisSecondary.Ticks) > 0 {
 		tickMin, tickMax := math.MaxFloat64, -math.MaxFloat64

defaults.go

@@ -205,6 +205,7 @@ func GetAlternateColor(index int) drawing.Color {
 var (
 	// DefaultAnnotationPadding is the padding around an annotation.
 	DefaultAnnotationPadding = Box{Top: 5, Left: 5, Right: 5, Bottom: 5}
+
 	// DefaultBackgroundPadding is the default canvas padding config.
 	DefaultBackgroundPadding = Box{Top: 5, Left: 5, Right: 5, Bottom: 5}
 )