problem with groovy swt: stuck with bind node processing and ComputedValues

[william Woodman]

been trying to look/use improve the groovy-swt/jface builder in groovy and hit some problems i need help to fix .

grooy-swt uses the eclipse data binding framework under the covers - most of the heavy lifting is in the BindFactory.class

whilst trying to use this i've been documenting as a i go and found a bug and i need to fix it and cant figure my way out.

so the problem i'm trying to look at is something in a builder that might look this

def shell= new SwtBuilder().shell {
...
     slider (id :'mySlider')
...
     label ('track slider', style: 'normal')
     text (text.bind ({mySlider1.selection})  // use implicit closure form
...

shell.doMainloop()

basically out of the box this doesnt work - so i have had ago at trying to understand how its working (got a temp fix) but it fails again if i use calc form like

     text (text.bind ({10+ mySlider1.selection})  // use implicit closure form

so whats the problem here. in the original code tree the code looks a bit like this

    def createClosureObservable(FactoryBuilderSupport builder, Binding binding) {
	//bit weird this not sure what this really doing - zippo documentation 
	def ctb = new ClosureTriggerBinding(new HashMap())
    	ctb.closure = binding.closure
		def fullbinding = ctb.createBinding(ctb, null)
		if (fullbinding.bindPaths.size() == 0) {
			throw new RuntimeException("A closure binding was used, but found no model properties")
		}
    	def modelObservables = []
		def modelBinding = new Binding() 
		// build array of observable's typically an array of 1 
			println "bind paths  " +  fullbinding.bindPaths.inspect()
		for (bp in fullbinding.bindPaths) {
			modelBinding.model = bp.extractNewValue(binding.closure)
			modelBinding.modelProperty = bp.children[0].propertyName // TODO: Recursive through all children
		println "model " + modelBinding.model + " and property " + modelBinding.modelProperty
	        modelObservables << createBeanObservable(builder, modelBinding)
		}

return [calculate: {
    		 		// TODO: Do we need get the values?
    			    def values = []
    			    for (model in modelObservables) {
    			    	values << model.getValue()
    			    }
    				def value = binding.closure.call()
					return value
    		    }] as ComputedValue
    }

now this fails on a number of fronts - the code return tries to caste a map as ComputedValue - but this doesnt work as the realm doesnt get set when you do it like this. Also despite the fact that the code generates a array of modelObservables[] by iterating through the closure for model references - it then ignoires all that and tries to return the evaluated closure as the ComputedValue.calculation () method.

I fixed the first by using simply returning the first item in the array - this works but only if the closure is a simple {model.prop} form by retuning the first entry

                        if (modelOberservables.size() ==1)
			    return modelObservables[0]  

This doesn't work if you try and use a form like {10+ mySlider1.selection}. Why? because that closureBindingTrigger stuff only returns the model.property and ignores the rest. - so the text tracks the slide value starting at 0 not starting at 10 as closure intended

so i tried to go back to the original form and fix the caste issues using the the latest groovy support for inner classes like this to correctly generate a ComputedValue

			def compVal = new ComputedValue () {
				protected calculate() {binding.closure.call()}
			}
                        println compVal.value  // delivers the calc value 
                        return compVal  //return the dynamic observable 

this kind of works if your closure doesnt contain anything complex so if the closure looks like {'some text'}, this is calculated and your text widget shows the correct string

if you try and do a GString closure like {"some text $someVar"} - the binding fails like this

Status WARNING: org.eclipse.core.databinding code=0 Could not change value of [e-mail] java.lang.IllegalArgumentException: argument type mismatch
java.lang.IllegalArgumentException: argument type mismatch
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.core.internal.databinding.beans.BeanPropertyHelper.writeProperty(BeanPropertyHelper.java:59)
at org.eclipse.core.internal.databinding.beans.BeanValueProperty.doSetValue(BeanValueProperty.java:51)
at org.eclipse.core.databinding.property.value.ValueProperty.setValue(ValueProperty.java:83)
at org.eclipse.core.internal.databinding.property.value.SimplePropertyObservableValue.doSetValue(SimplePropertyObservableValue.java:104)
at org.eclipse.core.databinding.observable.value.AbstractObservableValue.setValue(AbstractObservableValue.java:55)
at org.eclipse.core.databinding.observable.value.DecoratingObservableValue.setValue(DecoratingObservableValue.java:103)
at org.eclipse.core.internal.databinding.observable.masterdetail.DetailObservableValue.doSetValue(DetailObservableValue.java:134)
at org.eclipse.core.databinding.observable.value.AbstractObservableValue.setValue(AbstractObservableValue.java:55)
at org.eclipse.core.databinding.observable.value.DecoratingObservableValue.setValue(DecoratingObservableValue.java:103)
at org.eclipse.core.databinding.UpdateValueStrategy.doSet(UpdateValueStrategy.java:486)
at org.eclipse.core.databinding.ValueBinding$4.run(ValueBinding.java:197)

so my question is you want generate a ComputedValue object that correctly evaluates a closure with a GString part in it how do you do that ??

back to the original code base again - if i have many model.prop references in the closure {10 + model1.prop1 + model2.prop2} then the loop

		for (bp in fullbinding.bindPaths) {...

builds an array of modelObservables[] with two entries - but i cant generate a dynamically evaluated result that is the entire closure - including any non model+prop parts.

I am beginning to get out of my depth in framework code here for which theres little/zero documentation for

any one who can help i'd really appreciate it and i can then feed this fix and couple others back to the groovy swt leads to get mended

thanks in advance

[william Woodman]

updates - so some more playing and siddled closer to understanding

so part one -

in the original code tree

          ...
		def ctb = new ClosureTriggerBinding(new HashMap())
    	ctb.closure = binding.closure
		def fullbinding = ctb.createBinding(ctb, null)
		if (fullbinding.bindPaths.size() == 0) {
			throw new RuntimeException("A closure binding was used, but found no model properties")
		}
      ....

finally figured out what this is - the binding referred to here is the closure bindings when you set up a closure

e.g. if you have {some stuff $var} as closure then the bindings would be 1, and the value essentially the value of the part to substitute when doing a toString on your closure.

so what the code was doing was looking for a binding for the $var in your closure. It then was expecting this to be of form {model.param} and read the model name and the param name from the binding and builds an IObservable from that

this isn't so clever if you express a complex closure like {"hello $var " + model.param} as there are two closure bindings now

so i still only have a partial fix. If the closure is {model.param} i can just create an observable from this with BeanPropterties.value( .... and all works well

if its a complex compound closure such as {"hello $world " + model.param} the best i can do is create a ComputedValue object where the calculate method returns the value of the whole closure such as

ComputedValue cVal = new ComputedValue () {
  protected calculate () {theClosure.call().toString()}  
}

however whilst this is ok on first invocation it doesnt seem to observe the changes on the calc value and keeps giving you the cached value. so code in a builder like this

def shell = swt.shell {
	gridLayout(numColumns: 2)
	slider (id:'slider1', style:'none', selection: bind (model: model, modelProperty:'slideValue') ) 

	//label 'Slide value'
	def name = "william"
	def anotherName = " + marian"

	text (id: 'dynamicClosure',

		text: bind ({"hello $name $anotherName ${-> slider1.selection}"}),
		editable:false)
}
shell.doMainloop()

only binds once and as you drag the slider the ComputeValue object doesnt change. Only way i can seem to do that is to hold a ref to that computed value , and force a makeDirty() call on it and it will recalc then

So my question is how do you get a ComputedValue to automatically do the fresh when a value in the closure changes - but you dont change the closure itself?