setXAxisMaxLabelCount() not to affect Y Axis in HeatMapCharts

xchart/src/main/java/org/knowm/xchart/internal/chartpart/AxisTickCalculator_Category.java

@@ -63,36 +63,38 @@ private void calculate(List<?> categories, Series.DataType axisType) {
       throw new IllegalArgumentException("Unsupported max label count equal to 1");
     }
 
-    if (0 < xAxisMaxLabelCount && xAxisMaxLabelCount < categories.size()) {
-      List<Object> sparseCategories = new ArrayList<>();
-      double step = categories.size() / (double) (xAxisMaxLabelCount - 1);
-      for (double stepIdx = 0; Math.round(stepIdx) < categories.size(); stepIdx += step) {
-        int idx = (int) Math.round(stepIdx);
-        Object label = categories.get(idx);
-        sparseCategories.add(label);
+    if (this.axisDirection == Direction.X) {
+      if (0 < xAxisMaxLabelCount && xAxisMaxLabelCount < categories.size()) {
+        List<Object> sparseCategories = new ArrayList<>();
+        double step = categories.size() / (double) (xAxisMaxLabelCount - 1);
+        for (double stepIdx = 0; Math.round(stepIdx) < categories.size(); stepIdx += step) {
+          int idx = (int) Math.round(stepIdx);
+          Object label = categories.get(idx);
+          sparseCategories.add(label);
+        }
+
+        Object lastLabel = categories.get(categories.size() - 1);
+        sparseCategories.add(lastLabel);
+        categories = sparseCategories;
+
+        gridStep = (tickSpace / (categories.size() - 1));
+        firstPosition = 0;
       }
 
-      Object lastLabel = categories.get(categories.size() - 1);
-      sparseCategories.add(lastLabel);
-      categories = sparseCategories;
-
-      gridStep = (tickSpace / (categories.size() - 1));
-      firstPosition = 0;
-    }
-
-    // set up String formatters that may be encountered
-    if (axisType == Series.DataType.String) {
-      axisFormat = new Formatter_String();
-    } else if (axisType == Series.DataType.Number) {
-      axisFormat = new Formatter_Number(styler, axisDirection, minValue, maxValue);
-    } else if (axisType == Series.DataType.Date) {
-      if (styler.getDatePattern() == null) {
-        throw new RuntimeException("You need to set the Date Formatting Pattern!!!");
+      // set up String formatters that may be encountered
+      if (axisType == Series.DataType.String) {
+        axisFormat = new Formatter_String();
+      } else if (axisType == Series.DataType.Number) {
+        axisFormat = new Formatter_Number(styler, axisDirection, minValue, maxValue);
+      } else if (axisType == Series.DataType.Date) {
+        if (styler.getDatePattern() == null) {
+          throw new RuntimeException("You need to set the Date Formatting Pattern!!!");
+        }
+        SimpleDateFormat simpleDateformat =
+            new SimpleDateFormat(styler.getDatePattern(), styler.getLocale());
+        simpleDateformat.setTimeZone(styler.getTimezone());
+        axisFormat = simpleDateformat;
       }
-      SimpleDateFormat simpleDateformat =
-          new SimpleDateFormat(styler.getDatePattern(), styler.getLocale());
-      simpleDateformat.setTimeZone(styler.getTimezone());
-      axisFormat = simpleDateformat;
     }
 
     int counter = 0;

xchart/src/test/java/org/knowm/xchart/HeatMapChartTest.java

@@ -0,0 +1,76 @@
+package org.knowm.xchart;
+
+import java.io.ByteArrayOutputStream;
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.Arrays;
+import org.junit.Assert;
+import org.junit.Test;
+import org.knowm.xchart.internal.chartpart.Axis;
+import org.knowm.xchart.internal.chartpart.AxisPair;
+import org.knowm.xchart.internal.chartpart.Chart;
+import org.knowm.xchart.style.theme.XChartTheme;
+
+public class HeatMapChartTest {
+
+  java.util.List<Integer> xData;
+  java.util.List<String> yData;
+  java.util.List<Number[]> data;
+
+  {
+    int N = 12;
+    xData = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
+    yData =
+        Arrays.asList(
+            "January",
+            "February",
+            "March",
+            "April",
+            "May",
+            "June",
+            "July",
+            "August",
+            "September",
+            "October",
+            "November",
+            "December");
+    data = new ArrayList<>();
+    for (int i = 0; i < N; i++) {
+      for (int j = 0; j < N; j++) {
+        data.add(new Integer[] {i, j, (i * 2 + j * 3) % 7});
+      }
+    }
+  }
+
+  @Test
+  public void shouldApplyMaxLabelCountOnlyToXAxis() throws Exception {
+    // given
+    HeatMapChart chart = new HeatMapChart(800, 600);
+    chart.addSeries("only", xData, yData, data);
+    chart.getStyler().setTheme(new XChartTheme());
+
+    // when
+    chart.getStyler().setXAxisMaxLabelCount(5);
+    BitmapEncoder.saveBitmap(chart, new ByteArrayOutputStream(), BitmapEncoder.BitmapFormat.PNG);
+
+    // test
+    Assert.assertEquals(5, getXAxis(chart).getAxisTickCalculator().getTickLocations().size());
+    Assert.assertEquals(12, getYAxis(chart).getAxisTickCalculator().getTickLocations().size());
+  }
+
+  private AxisPair<?, ?> getAxisPair(Chart<?, ?> chart) throws ReflectiveOperationException {
+    Field f = Chart.class.getDeclaredField("axisPair");
+    f.setAccessible(true);
+    return (AxisPair<?, ?>) f.get(chart);
+  }
+
+  public Axis<?, ?> getXAxis(Chart<?, ?> chart) throws ReflectiveOperationException {
+    return getAxisPair(chart).getXAxis();
+  }
+
+  public Axis<?, ?> getYAxis(Chart<?, ?> chart) throws ReflectiveOperationException {
+    Field f = AxisPair.class.getDeclaredField("yAxis");
+    f.setAccessible(true);
+    return (Axis<?, ?>) f.get(getAxisPair(chart));
+  }
+}