Handle missing min/max gracefully for sliders/scrollbars

[imagejan]

Currently, the UI hangs when trying to use a numeric parameter with style=slider, but min or max undefined:

#@ int (style=slider) a

This should be handled gracefully, by checking for softMin != null and softMax != null here:

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

Lines 102 to 124 in 221d3c6

	// 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);
	}
	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);
	}

If no slider or scroll bar can be rendered, we should fallback to the standard textfield/spinner combination and log a warning message.

[ctrueden]

I did some digging. The reason it freezes is not because min and max are null—that would throw an NPE after all. It's because min defaults to Integer.MIN_VALUE and max to Integer.MAX_VALUE. The UI builder then proceeds to try to make a slider or scroll bar with a massively huge range, and the CPU goes to 100% indefinitely. The problem is this and that lines of code in the DefaultWidgetModel.

A possible fix would be to change the code that creates the JScrollBar or JSlider to be more conservative about what it feeds to those constructors. This would also guard against the case of explicit min="-1000000000", max="1000000000" sorts of inputs.

[imagejan]

Thanks for digging, @ctrueden!
I think we can tackle this at the same time as allowing non-integer step sizes in sliders (see #31), by adjusting the step size in case the number of possible steps gets unreasonably high (the acceptable limit might have to be found by testing with different settings).

[ctrueden]

I believe I have fixed the integer cases. Handling non-integers will be more involved, though.