JAL-3206 avoid divide by zero when threshold is graphMin / graphMax

diff --git a/src/jalview/schemes/AnnotationColourGradient.java b/src/jalview/schemes/AnnotationColourGradient.java
index c28ea5f..c74fdbc 100755 (executable)
--- a/src/jalview/schemes/AnnotationColourGradient.java
+++ b/src/jalview/schemes/AnnotationColourGradient.java
@@ -185,7 +185,7 @@ public class AnnotationColourGradient extends FollowerColourScheme
       }
       else
       {
-        seqannot = new IdentityHashMap<SequenceI, AlignmentAnnotation>();
+        seqannot = new IdentityHashMap<>();
       }
       // resolve the context containing all the annotation for the sequence
       AnnotatedCollectionI alcontext = alignment instanceof AlignmentI
@@ -414,14 +414,17 @@ public class AnnotationColourGradient extends FollowerColourScheme
             && aboveAnnotationThreshold == ABOVE_THRESHOLD
             && value >= ann.threshold.value)
     {
-      range = (value - ann.threshold.value)
+      range = ann.graphMax == ann.threshold.value ? 1f
+              : (value - ann.threshold.value)
               / (ann.graphMax - ann.threshold.value);
     }
     else if (thresholdIsMinMax && ann.threshold != null
             && aboveAnnotationThreshold == BELOW_THRESHOLD
             && value <= ann.threshold.value)
     {
-      range = (value - ann.graphMin) / (ann.threshold.value - ann.graphMin);
+      range = ann.graphMin == ann.threshold.value ? 0f
+              : (value - ann.graphMin)
+                      / (ann.threshold.value - ann.graphMin);
     }
     else
     {

diff --git a/test/jalview/schemes/AnnotationColourGradientTest.java b/test/jalview/schemes/AnnotationColourGradientTest.java
index b7a5164..be8b58d 100644 (file)
--- a/test/jalview/schemes/AnnotationColourGradientTest.java
+++ b/test/jalview/schemes/AnnotationColourGradientTest.java
@@ -124,6 +124,18 @@ public class AnnotationColourGradientTest
       Color result = testee.shadeCalculation(ann, col);
       assertEquals(result, expected, "for column " + col);
     }
+
+    /*
+     * test for boundary case threshold == graphMax (JAL-3206)
+     */
+    float thresh = ann.threshold.value;
+    ann.threshold.value = ann.graphMax;
+    Color result = testee.shadeCalculation(ann, WIDTH - 1);
+    assertEquals(result, maxColour);
+    testee.setThresholdIsMinMax(false);
+    result = testee.shadeCalculation(ann, WIDTH - 1);
+    assertEquals(result, maxColour);
+    ann.threshold.value = thresh; // reset
   }
 
   /**
@@ -174,6 +186,18 @@ public class AnnotationColourGradientTest
       Color result = testee.shadeCalculation(ann, col);
       assertEquals(result, expected, "for column " + col);
     }
+
+    /*
+     * test for boundary case threshold == graphMin (JAL-3206)
+     */
+    float thresh = ann.threshold.value;
+    ann.threshold.value = ann.graphMin;
+    Color result = testee.shadeCalculation(ann, 0);
+    assertEquals(result, minColour);
+    testee.setThresholdIsMinMax(false);
+    result = testee.shadeCalculation(ann, 0);
+    assertEquals(result, minColour);
+    ann.threshold.value = thresh; // reset
   }
 
   /**