From 231ff42904c42c330209fa755fca34446b62cfcb Mon Sep 17 00:00:00 2001
From: Alexey Kirpichnikov <alex.kirp@gmail.com>
Date: Thu, 23 May 2019 15:59:57 +0500
Subject: [PATCH] Explicitly prevent empty ranges

---
 tick.go      |  4 ++++
 tick_test.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/tick.go b/tick.go
index d5d5a7b..be94dd3 100644
--- a/tick.go
+++ b/tick.go
@@ -133,6 +133,10 @@ func GeneratePrettyContinuousTicks(r Renderer, ra Range, isVertical bool, style
 
 	rangeMin, rangeMax := ra.GetMin(), ra.GetMax()
 
+	if rangeMin >= rangeMax || ra.GetDomain() == 0 {
+		return []Tick{}
+	}
+
 	renderedLabelExample := vf(rangeMin)
 	style.GetTextOptions().WriteToRenderer(r)
 	renderedLabelSizePx := r.MeasureText(renderedLabelExample)
diff --git a/tick_test.go b/tick_test.go
index 446a098..b88ee0a 100644
--- a/tick_test.go
+++ b/tick_test.go
@@ -95,6 +95,37 @@ func TestGenerateContinuousPrettyTicks(t *testing.T) {
 		{Label: "60.00", Value: 60}})
 }
 
+func TestGenerateContinuousPrettyTicksForEmptyRange(t *testing.T) {
+	assert := assert.New(t)
+
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+
+	r, err := PNG(1024, 1024)
+	assert.Nil(err)
+	r.SetFont(f)
+
+	ra := &ContinuousRange{
+		Min:    1.0,
+		Max:    1.0,
+		Domain: 256,
+	}
+
+	vf := FloatValueFormatter
+
+	ticks := GeneratePrettyContinuousTicks(r, ra, false, Style{}, vf)
+	assert.Empty(ticks)
+
+	ra = &ContinuousRange{
+		Min:    1.0,
+		Max:    2.0,
+		Domain: 0,
+	}
+
+	ticks = GeneratePrettyContinuousTicks(r, ra, false, Style{}, vf)
+	assert.Empty(ticks)
+}
+
 func TestGeneratePrettyTicksForVerySmallRange(t *testing.T) {
 	assert := assert.New(t)