don't annotate pie chart slice if not enough room

xchart-demo/src/main/java/org/knowm/xchart/demo/XChartDemo.java

@@ -61,6 +61,7 @@ import org.knowm.xchart.demo.charts.line.LineChart06;
 import org.knowm.xchart.demo.charts.line.LineChart07;
 import org.knowm.xchart.demo.charts.pie.PieChart01;
 import org.knowm.xchart.demo.charts.pie.PieChart02;
+import org.knowm.xchart.demo.charts.pie.PieChart03;
 import org.knowm.xchart.demo.charts.realtime.RealtimeChart01;
 import org.knowm.xchart.demo.charts.realtime.RealtimeChart02;
 import org.knowm.xchart.demo.charts.realtime.RealtimeChart03;
@@ -228,7 +229,10 @@ public class XChartDemo extends JPanel implements TreeSelectionListener {
     defaultMutableTreeNode = new DefaultMutableTreeNode(new ChartInfo("PieChart01 - Pie Chart with 4 Slices", new PieChart01().getChart()));
     category.add(defaultMutableTreeNode);
 
-    defaultMutableTreeNode = new DefaultMutableTreeNode(new ChartInfo("PieChart012 - Pie Chart Custom Color Palette", new PieChart02().getChart()));
+    defaultMutableTreeNode = new DefaultMutableTreeNode(new ChartInfo("PieChart02 - Pie Chart Custom Color Palette", new PieChart02().getChart()));
+    category.add(defaultMutableTreeNode);
+
+    defaultMutableTreeNode = new DefaultMutableTreeNode(new ChartInfo("PieChart03 - Pie Chart Custom GGPlot2 Theme", new PieChart03().getChart()));
     category.add(defaultMutableTreeNode);
 
     // Line category

xchart-demo/src/main/java/org/knowm/xchart/demo/charts/pie/PieChart03.java

+/**
+ * Copyright 2015-2016 Knowm Inc. (http://knowm.org) and contributors.
+ * Copyright 2011-2015 Xeiam LLC (http://xeiam.com) and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.knowm.xchart.demo.charts.pie;
+
+import org.knowm.xchart.ChartBuilder_Pie;
+import org.knowm.xchart.Chart_Pie;
+import org.knowm.xchart.SwingWrapper;
+import org.knowm.xchart.demo.charts.ExampleChart;
+import org.knowm.xchart.internal.style.Styler.ChartTheme;
+
+/**
+ * Pie Chart with 5 Slices and customization
+ * <p>
+ * Demonstrates the following:
+ * <ul>
+ * <li>Pie Chart
+ * <li>ChartBuilderPie
+ * <li>GGPlot2 Theme
+ */
+public class PieChart03 implements ExampleChart<Chart_Pie> {
+
+  public static void main(String[] args) {
+
+    ExampleChart<Chart_Pie> exampleChart = new PieChart03();
+    Chart_Pie chart = exampleChart.getChart();
+    new SwingWrapper(chart).displayChart();
+  }
+
+  @Override
+  public Chart_Pie getChart() {
+
+    // Create Chart
+    Chart_Pie chart = new ChartBuilder_Pie().width(400).height(500).title(getClass().getSimpleName()).theme(ChartTheme.GGPlot2).build();
+    chart.addSeries("Prague", 2);
+    chart.addSeries("Dresden", 4);
+    chart.addSeries("Munich", 34);
+    chart.addSeries("Hamburg", 22);
+    chart.addSeries("Berlin", 29);
+
+    return chart;
+  }
+
+}

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

@@ -136,17 +136,50 @@ public class PlotContent_Pie<ST extends Styler, S extends Series> extends PlotCo
       double xOffset = xCenter + Math.cos(Math.toRadians(angle)) * (pieBounds.getWidth() / 2 * stylerPie.getAnnotationDistance());
       double yOffset = yCenter - Math.sin(Math.toRadians(angle)) * (pieBounds.getHeight() / 2 * stylerPie.getAnnotationDistance());
 
-      g.setColor(stylerPie.getChartFontColor());
-      g.setFont(stylerPie.getChartTitleFont());
-
+      // get annotation width
       Shape shape = textLayout.getOutline(null);
-      AffineTransform orig = g.getTransform();
-      AffineTransform at = new AffineTransform();
-      at.translate(xOffset, yOffset);
-      g.transform(at);
-      g.fill(shape);
-      g.setTransform(orig);
-
+      Rectangle2D annotationBounds = shape.getBounds2D();
+      double annotationWidth = annotationBounds.getWidth();
+      // System.out.println("annotationWidth= " + annotationWidth);
+      double annotationHeight = annotationBounds.getHeight();
+      // System.out.println("annotationHeight= " + annotationHeight);
+
+      // get slice area
+      double xOffset1 = xCenter + Math.cos(Math.toRadians(startAngle)) * (pieBounds.getWidth() / 2 * stylerPie.getAnnotationDistance());
+      double yOffset1 = yCenter - Math.sin(Math.toRadians(startAngle)) * (pieBounds.getHeight() / 2 * stylerPie.getAnnotationDistance());
+      double xOffset2 = xCenter + Math.cos(Math.toRadians((arcAngle + startAngle))) * (pieBounds.getWidth() / 2 * stylerPie.getAnnotationDistance());
+      double yOffset2 = yCenter - Math.sin(Math.toRadians((arcAngle + startAngle))) * (pieBounds.getHeight() / 2 * stylerPie.getAnnotationDistance());
+      // System.out.println("xOffset1= " + xOffset1);
+      // System.out.println("yOffset1= " + yOffset1);
+      // System.out.println("xOffset2= " + xOffset2);
+      // System.out.println("yOffset2= " + yOffset2);
+      double xDiff = Math.abs(xOffset1 - xOffset2);
+      double yDiff = Math.abs(yOffset1 - yOffset2);
+      // System.out.println("xDiff= " + xDiff);
+      // System.out.println("yDiff= " + yDiff);
+      // double max = Math.max(xDiff, yDiff);
+      // System.out.println(" ================== ");
+      boolean annotationWillFit = false;
+      if (xDiff > yDiff) {// assume more vertically orientated slice
+        if (annotationWidth < xDiff) {
+          annotationWillFit = true;
+        }
+      }
+      else if (xDiff < yDiff) {// assume more horizontally orientated slice
+        if (annotationHeight < yDiff) {
+          annotationWillFit = true;
+        }
+      }
+      if (annotationWillFit) {
+        g.setColor(stylerPie.getChartFontColor());
+        g.setFont(stylerPie.getChartTitleFont());
+        AffineTransform orig = g.getTransform();
+        AffineTransform at = new AffineTransform();
+        at.translate(xOffset, yOffset);
+        g.transform(at);
+        g.fill(shape);
+        g.setTransform(orig);
+      }
       // // Tick Mark
       // xCenter = pieBounds.getX() + pieBounds.getWidth() / 2;
       // yCenter = pieBounds.getY() + pieBounds.getHeight() / 2;