JENKINS-16580: crop plots to fit screen with extra margin

src/main/java/hudson/plugins/jacoco/model/CoverageGraphLayout.java

@@ -157,8 +157,14 @@ public Number getValue(Coverage c)
 	static class Axis
 	{
 		private String label = null;
+		private int crop = -1;
 		private boolean skipZero = false;
 
+		public boolean isCrop()
+		{
+			return crop != -1;
+		}
+
 		public boolean isSkipZero()
 		{
 			return skipZero;
@@ -168,6 +174,11 @@ public String getLabel()
 		{
 			return label;
 		}
+
+		public int getCrop()
+		{
+			return crop;
+		}
 	}
 
 	static class Plot
@@ -225,6 +236,18 @@ private void assureAxis()
 		if (axes.isEmpty()) axis();
 	}
 
+	public CoverageGraphLayout crop()
+	{
+		return crop(5);
+	}
+
+	public CoverageGraphLayout crop(int marginInPercent)
+	{
+		assureAxis();
+		axes.peek().crop = marginInPercent;
+		return this;
+	}
+
 	public CoverageGraphLayout label(String label)
 	{
 		assureAxis();

src/main/java/hudson/plugins/jacoco/model/CoverageObject.java

@@ -33,6 +33,7 @@
 import org.jfree.chart.axis.CategoryAxis;
 import org.jfree.chart.axis.CategoryLabelPositions;
 import org.jfree.chart.axis.NumberAxis;
+import org.jfree.chart.axis.ValueAxis;
 import org.jfree.chart.plot.CategoryPlot;
 import org.jfree.chart.plot.PlotOrientation;
 import org.jfree.data.category.CategoryDataset;
@@ -393,6 +394,7 @@ protected Map<Axis, DataSetBuilder<String, NumberOnlyBuildLabel>> createDataSetB
 				for (Axis axis : layout.getAxes())
 				{
 					builders.put(axis, new DataSetBuilder<String, NumberOnlyBuildLabel>());
+					if (axis.isCrop()) bounds.put(axis, new Bounds());
 				}
 
 				Map<Plot, Number> last = new HashMap<Plot, Number>();
@@ -406,6 +408,7 @@ protected Map<Axis, DataSetBuilder<String, NumberOnlyBuildLabel>> createDataSetB
 						if (axis.isSkipZero() && (value == null || value.floatValue() == 0f)) value = null;
 						if (value != null)
 						{
+							if (axis.isCrop()) bounds.get(axis).update(value);
 							last.put(plot, value);
 						}
 						else
@@ -428,6 +431,20 @@ abstract class GraphImpl extends Graph {
 
 		private CoverageObject<SELF> obj;
 		private CoverageGraphLayout layout;
+		protected Map<Axis,Bounds> bounds=new HashMap<Axis, Bounds>();
+
+		protected class Bounds
+		{
+			float min=Float.MAX_VALUE;
+			float max=Float.MIN_VALUE;
+
+			public void update(Number value)
+			{
+				float v=value.floatValue();
+				if (min>v) min=v;
+				if (max<v) max=v+1;
+			}
+		}
 
 		public GraphImpl(CoverageObject<SELF> obj, Calendar timestamp, int defaultW, int defaultH, CoverageGraphLayout layout) {
 			super(timestamp, defaultW, defaultH);
@@ -481,12 +498,22 @@ protected JFreeChart createGraph() {
 				NumberAxis numberAxis = new NumberAxis(axis.getLabel());
 				plot.setRangeAxis(axisId, numberAxis);
 				numberAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits()); //TODO
+				setBounds(axis, numberAxis);
 				axisId++;
 			}
 
 			layout.apply(chart);
 			return chart;
 		}
+
+		private void setBounds(Axis a, ValueAxis axis)
+		{
+			if (!a.isCrop()) return;
+			Bounds bounds = this.bounds.get(a);
+			float border = (bounds.max - bounds.min) / 100 * a.getCrop();
+			axis.setUpperBound(bounds.max + border);
+			axis.setLowerBound(Math.max(0, bounds.min - border));
+		}
 	}
 
 	@Override

src/test/java/hudson/plugins/jacoco/model/CoverageObjectGraphTest.java

@@ -103,6 +103,30 @@ public void multipleAccessAndDifferentCoverageType() throws IOException
 		assertGraph(chart, "multiple.png");
 	}
 
+	@Test
+	public void crop5() throws IOException
+	{
+		CoverageGraphLayout layout = new CoverageGraphLayout()
+				.baseStroke(2f)
+				.axis().crop(5).skipZero()
+				.plot().type(CoverageType.BRANCH).value(CoverageValue.PERCENTAGE).color(Color.RED);
+
+		JFreeChart chart = createTestCoverage().createGraph(new GregorianCalendar(), WIDTH, HEIGHT, layout).getGraph();
+		assertGraph(chart, "crop5.png");
+	}
+
+	@Test
+	public void crop100() throws IOException
+	{
+		CoverageGraphLayout layout = new CoverageGraphLayout()
+				.baseStroke(2f)
+				.axis().crop(100).skipZero()
+				.plot().type(CoverageType.BRANCH).value(CoverageValue.PERCENTAGE).color(Color.RED);
+
+		JFreeChart chart = createTestCoverage().createGraph(new GregorianCalendar(), WIDTH, HEIGHT, layout).getGraph();
+		assertGraph(chart, "crop100.png");
+	}
+
 	@Test
 	public void skipZero() throws IOException
 	{