Fix for bug #64, exception on extreme zoom on NumberAxis

jfree · Oct 24, 2020 · 6dc65fc · 6dc65fc
1 parent 7881741
commit 6dc65fc
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diff --git a/README.md b/README.md
@@ -74,7 +74,8 @@ History
 
 ##### Version 1.6.0 (not yet released)
 - update required JDK to version 1.8;
-- modify buffer in ChartPanel to handle high DPI displays (bug #170)
+- modify buffer in ChartPanel to handle high DPI displays (bug #170);
+- fix for exception on extreme zoom on NumberAxis (bug #64);
 - added generics 
 - DefaultIntervalCategoryDataset no longer allows null keys in constructor (this
   is a consequence of introducing generics)

diff --git a/src/main/java/org/jfree/chart/axis/NumberAxis.java b/src/main/java/org/jfree/chart/axis/NumberAxis.java
@@ -776,27 +776,36 @@ protected void selectHorizontalAutoTickUnit(Graphics2D g2,
 
         TickUnit unit = getTickUnit();
         TickUnitSource tickUnitSource = getStandardTickUnits();
-        // we should use the current tick unit if it gives a count in the range
-        // 2 to 40 otherwise just estimate one that will give a count <= 20
+
+        // we should start with the current tick unit if it gives a count in 
+        // the range 3 to 40 otherwise estimate one that will give a count <= 10
         double length = getRange().getLength();
         int count = (int) (length / unit.getSize());
-        if (count < 2 || count > 40) {
-            unit = tickUnitSource.getCeilingTickUnit(length / 20);
+        if (count < 3 || count > 40) {
+            unit = tickUnitSource.getCeilingTickUnit(length / 10);
         }
-        double tickLabelWidth = estimateMaximumTickLabelWidth(g2, unit);
 
+        // now consider the label size relative to the width of the tick unit
+        // and make a guess at the ideal size
         TickUnit unit1 = tickUnitSource.getCeilingTickUnit(unit);
+        double tickLabelWidth = estimateMaximumTickLabelWidth(g2, unit1);
         double unit1Width = lengthToJava2D(unit1.getSize(), dataArea, edge);
-
-        // then extrapolate...
+        NumberTickUnit unit2 = (NumberTickUnit) unit1;
         double guess = (tickLabelWidth / unit1Width) * unit1.getSize();
-        NumberTickUnit unit2 = (NumberTickUnit) 
-                tickUnitSource.getCeilingTickUnit(guess);
-        double unit2Width = lengthToJava2D(unit2.getSize(), dataArea, edge);
 
-        tickLabelWidth = estimateMaximumTickLabelWidth(g2, unit2);
-        if (tickLabelWidth > unit2Width) {
-            unit2 = (NumberTickUnit) tickUnitSource.getLargerTickUnit(unit2);
+        // due to limitations of double precision, when you zoom very far into
+        // a chart, eventually the visible axis range will get reported as 
+        // having length 0, and then 'guess' above will be infinite ... in that 
+        // case we'll just stick with the tick unit we have, it's better than 
+        // throwing an exception 
+        // https://github.com/jfree/jfreechart/issues/64
+        if (Double.isFinite(guess)) {
+            unit2 = (NumberTickUnit) tickUnitSource.getCeilingTickUnit(guess);
+            double unit2Width = lengthToJava2D(unit2.getSize(), dataArea, edge);
+            tickLabelWidth = estimateMaximumTickLabelWidth(g2, unit2);
+            if (tickLabelWidth > unit2Width) {
+                unit2 = (NumberTickUnit) tickUnitSource.getLargerTickUnit(unit2);
+            }
         }
         setTickUnit(unit2, false, false);
     }
@@ -833,7 +842,6 @@ protected void selectVerticalAutoTickUnit(Graphics2D g2,
         if (tickLabelHeight > unit2Height) {
             unit2 = (NumberTickUnit) tickUnits.getLargerTickUnit(unit2);
         }
-
         setTickUnit(unit2, false, false);
 
     }

diff --git a/src/main/java/org/jfree/chart/axis/NumberTickUnit.java b/src/main/java/org/jfree/chart/axis/NumberTickUnit.java
@@ -2,7 +2,7 @@
  * JFreeChart : a free chart library for the Java(tm) platform
  * ===========================================================
  *
- * (C) Copyright 2000-2016, by Object Refinery Limited and Contributors.
+ * (C) Copyright 2000-2020, by Object Refinery Limited and Contributors.
  *
  * Project Info:  http://www.jfree.org/jfreechart/index.html
  *
@@ -147,7 +147,8 @@ public boolean equals(Object obj) {
      */
     @Override
     public String toString() {
-        return "[size=" + this.valueToString(this.getSize()) + "]";
+        return "[NumberTickUnit: size=" + this.valueToString(this.getSize()) 
+                + ", formatter=" + this.formatter + "]";
     }
 
     /**

diff --git a/src/main/java/org/jfree/chart/axis/NumberTickUnitSource.java b/src/main/java/org/jfree/chart/axis/NumberTickUnitSource.java
@@ -2,7 +2,7 @@
  * JFreeChart : a free chart library for the Java(tm) platform
  * ===========================================================
  *
- * (C) Copyright 2000-2016, by Object Refinery Limited and Contributors.
+ * (C) Copyright 2000-2020, by Object Refinery Limited and Contributors.
  *
  * Project Info:  http://www.jfree.org/jfreechart/index.html
  *

diff --git a/src/main/java/org/jfree/chart/axis/StandardTickUnitSource.java b/src/main/java/org/jfree/chart/axis/StandardTickUnitSource.java
@@ -2,7 +2,7 @@
  * JFreeChart : a free chart library for the Java(tm) platform
  * ===========================================================
  *
- * (C) Copyright 2000-2016, by Object Refinery Limited and Contributors.
+ * (C) Copyright 2000-2020, by Object Refinery Limited and Contributors.
  *
  * Project Info:  http://www.jfree.org/jfreechart/index.html
  *
@@ -27,16 +27,11 @@
  * ---------------------------
  * StandardTickUnitSource.java
  * ---------------------------
- * (C) Copyright 2003-2008, by Object Refinery Limited.
+ * (C) Copyright 2003-2020, by Object Refinery Limited.
  *
  * Original Author:  David Gilbert (for Object Refinery Limited);
  * Contributor(s):   -;
  *
- * Changes
- * -------
- * 23-Sep-2003 : Version 1 (DG);
- * 25-Oct-2007 : Implemented Serializable and equals() method (DG);
- *
  */
 
 package org.jfree.chart.axis;