SwingNumberWidget: improve sliders and scroll bars

This fixes the following issues:

* If a slider had a span (max - min) more than Integer.MAX_VALUE, it
  would hang at 100% CPU forever, probably due to a Java bug. We work
  around this by refusing to add a slider in this case, and logging a
  warning to the user about it.
* If a slider had a large min and/or max value, the labels would get
  very long and bleed into each other. We work around this by: a)
  showing only the min and max labels, without the three intermediate
  labels, when the min and/or max label string length is 5 or more;
  and b) hiding the labels altogether when the min and/or max label
  string length is 10 or more.
* If the number of ticks is large, the slider still tries to paint
  them all. So now we only paint the ticks if there are less than 100.
* If a scroll bar has a minimum value of Integer.MIN_VALUE, it does
  something special, according to the documentation. So we avoid that
  case by bumping up the min by one if that happens.
* If the widget model somehow returns null for min, max or step,
  it would throw an NPE (although in practice this does not happen with
  DefaultWidgetModel). But still, the code is defensive about that now.

Closes #32.

Author: ctrueden

src/main/java/org/scijava/ui/swing/widget/SwingNumberWidget.java

@@ -52,6 +52,7 @@
 import javax.swing.event.ChangeEvent;
 import javax.swing.event.ChangeListener;
 
+import org.scijava.log.LogService;
 import org.scijava.module.ModuleService;
 import org.scijava.plugin.Parameter;
 import org.scijava.plugin.Plugin;
@@ -76,6 +77,9 @@ public class SwingNumberWidget extends SwingInputWidget<Number> implements
 	@Parameter
 	private ModuleService moduleService;
 
+	@Parameter
+	private LogService log;
+
 	private JScrollBar scrollBar;
 	private JSlider slider;
 	private JSpinner spinner;
@@ -101,26 +105,10 @@ public void set(final WidgetModel model) {
 
 		// add optional widgets, if specified
 		if (model.isStyle(NumberWidget.SCROLL_BAR_STYLE)) {
-			int smx = softMax.intValue();
-			if (smx < Integer.MAX_VALUE) smx++;
-			scrollBar =
-				new JScrollBar(Adjustable.HORIZONTAL, softMin.intValue(), 1, softMin
-					.intValue(), smx);
-			scrollBar.setUnitIncrement(stepSize.intValue());
-			setToolTip(scrollBar);
-			getComponent().add(scrollBar);
-			scrollBar.addAdjustmentListener(this);
+			addScrollBar(softMin, softMax, stepSize);
 		}
 		else if (model.isStyle(NumberWidget.SLIDER_STYLE)) {
-			slider =
-				new JSlider(softMin.intValue(), softMax.intValue(), softMin.intValue());
-			slider.setMajorTickSpacing((softMax.intValue() - softMin.intValue()) / 4);
-			slider.setMinorTickSpacing(stepSize.intValue());
-			slider.setPaintLabels(true);
-			slider.setPaintTicks(true);
-			setToolTip(slider);
-			getComponent().add(slider);
-			slider.addChangeListener(this);
+			addSlider(softMin, softMax, stepSize);
 		}
 
 		// add spinner widget
@@ -174,6 +162,59 @@ else if (source == spinner) {
 
 	// -- Helper methods --
 
+	private void addScrollBar(final Number min, final Number max,
+		final Number step)
+	{
+		if (min == null || max == null || step == null) {
+			log.warn("Invalid min/max/step; cannot render scroll bar");
+			return;
+		}
+		int mn = min.intValue();
+		if (mn == Integer.MIN_VALUE) mn = Integer.MIN_VALUE + 1;
+		int mx = max.intValue();
+		if (mx < Integer.MAX_VALUE) mx++;
+		final int st = step.intValue();
+
+		scrollBar = new JScrollBar(Adjustable.HORIZONTAL, mn, 1, mn, mx);
+		scrollBar.setUnitIncrement(st);
+		setToolTip(scrollBar);
+		getComponent().add(scrollBar);
+		scrollBar.addAdjustmentListener(this);
+	}
+
+	private void addSlider(final Number min, final Number max,
+		final Number step)
+	{
+		if (min == null || max == null || step == null) {
+			log.warn("Invalid min/max/step; cannot render slider");
+			return;
+		}
+		final int mn = min.intValue();
+		final int mx = max.intValue();
+		final int st = step.intValue();
+		if ((long) mx - mn > Integer.MAX_VALUE) {
+			log.warn("Slider span too large; max - min < 2^31 required.");
+			return;
+		}
+		final int span = mx - mn;
+
+		slider = new JSlider(mn, mx, mn);
+
+		// Compute optimal major ticks and labels.
+		final int labelWidth = Math.max(("" + mn).length(), ("" + mx).length());
+		slider.setMajorTickSpacing(labelWidth < 5 ? span / 4 : span);
+		slider.setPaintLabels(labelWidth < 10);
+
+		// Compute optimal minor ticks.
+		final int stepCount = span / st + 1;
+		slider.setMinorTickSpacing(st);
+		slider.setPaintTicks(stepCount < 100);
+
+		setToolTip(slider);
+		getComponent().add(slider);
+		slider.addChangeListener(this);
+	}
+
 	/**
 	 * Limit component width to a certain maximum. This is a HACK to work around
 	 * an issue with Double-based spinners that attempt to size themselves very