[Solved] Volatile function in C++

[saleem145]

Hello,

How do I define a volatile function in a C++ addin??

Thanks,

Saleem

[saleem145]

Some info here --

http://wiki.openoffice.org/wiki/Documen ... et_Add-Ins

Ideally I need a full example....

Saleem

[Charlie Young]

After some hesitation I took this up, since I was curious myself about how this works.

First thing I tried was to just translate the Java example into c++, but after a few hours of frustration I backed off and tried it in Python, and after a considerable struggle I got that working.

Then I went back to the c++ again. I don't want to go over all the stumbling blocks I encountered (though I'll mention a few), but I now have that working, I think. This isn't really useful for much besides illustrating the basic techniques, but since we've got to start somewhere, here goes...

The idl

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#include <com/sun/star/uno/XInterface.idl>
#include <com/sun/star/lang/XInitialization.idl>
#include <com/sun/star/lang/XServiceName.idl>
#include <com/sun/star/lang/XLocalizable.idl>
#include <com/sun/star/sheet/XVolatileResult.idl>

module com {module volresult
{
	interface XVolatile
{ 
    string IncrementCounter( [in] string aName );
    com::sun::star::sheet::XVolatileResult getCounter( [in] string aName );
};
service Volatile
{
interface XVolatile;
interface com::sun::star::sheet::XVolatileResult;
interface com::sun::star::lang::XInitialization;
interface com::sun::star::lang::XServiceName;
};};
};

My first mistake was forgetting that "volatile" is a c++ keyword, and I originally used "volatile" instead of "volresult" in the namespace. Using Volatile as the service name doesn't cause problems, of course, since c++ is case sensitive.

First we need to define a ResultListener. To do OpenOffice listeners in c++, it turns out that helpers are called for, so

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#include <cppuhelper/implbase1.hxx>

then we do

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typedef ::cppu::WeakImplHelper1< ::com::sun::star::sheet::XResultListener> ResultListenerHelper;

And our listener class then looks like

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class MyResultListener: public ResultListenerHelper{
public:
	void SAL_CALL modified(const ResultEvent &) throw (::com::sun::star::uno::RuntimeException);
	void SAL_CALL disposing(const EventObject &) throw (::com::sun::star::uno::RuntimeException);
};

void SAL_CALL MyResultListener::modified(const ResultEvent & aEvent) throw (::com::sun::star::uno::RuntimeException)
{
	return;
}

void SAL_CALL MyResultListener::disposing(const EventObject & aEvent) throw (::com::sun::star::uno::RuntimeException)
{
	return;
}

Then for the result object, that is the ExampleAddInResult class from the Java example, we can do

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typedef ::cppu::WeakImplHelper1< ::com::sun::star::sheet::XVolatileResult> VolatileResultHelper;

then

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class ExampleAddInResult: public VolatileResultHelper {
private:
	OUString aName;
	long nValue;
	vector<Reference< XResultListener >> myListeners;
	com::sun::star::sheet::ResultEvent getResult();
public:
	ExampleAddInResult(OUString);
	ExampleAddInResult();
	void SAL_CALL addResultListener(const Reference<XResultListener> & aListener) throw (::com::sun::star::uno::RuntimeException);
    void SAL_CALL removeResultListener(const Reference<XResultListener> & aListener) throw (::com::sun::star::uno::RuntimeException);
		
	void incrementValue() {
		long i;
		++nValue;
		com::sun::star::sheet::ResultEvent aEvent = getResult();
		for(i = 0;i < myListeners.size(); i++) 
			myListeners[i]->modified(aEvent);
		
    }
	
};

void SAL_CALL ExampleAddInResult::addResultListener(const Reference<XResultListener> & aListener) throw (::com::sun::star::uno::RuntimeException) {
	myListeners.push_back(aListener);
	// immediately notify of initial value
	com::sun::star::sheet::ResultEvent aEvent = getResult();
	myListeners.back()->modified(aEvent);
}

void SAL_CALL ExampleAddInResult::removeResultListener(const Reference<XResultListener> & aListener) throw (::com::sun::star::uno::RuntimeException) {
	myListeners.pop_back();
}

Constructors:

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ExampleAddInResult::ExampleAddInResult(OUString aNewName)
{
	aName = aNewName;
	myListeners.reserve(10); 
	nValue = 0;
}

ExampleAddInResult::ExampleAddInResult()
{
	aName = OUString();
	nValue = 0;
}

The .reserve(10) isn't terribly important, but I will mention that handling the listeners was ultimately what gave me the most difficulty.

The getResult method is also key. In the Java example, they just do aEvent.Source = this (= self in Python), but c++ is fussier, and one need to explicitly get a Reference<XInterface>. I tried several thing, but eventually lucked onto something that worked.

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com::sun::star::sheet::ResultEvent ExampleAddInResult::getResult()
{
	com::sun::star::sheet::ResultEvent aEvent;
	OUString ou;
	Reference< XInterface > x( static_cast< lang::XTypeProvider * >( this ) );
	aEvent.Value <<= aName + OUString( RTL_CONSTASCII_USTRINGPARAM(" ") ) + ou.valueOf((sal_Int32) nValue);
	aEvent.Source = x;
	return aEvent;
}

Moving on, in the Java example the result objects are stored as (key, value) pairs in a hash table. In c++ this is an unordered_map, so in the VolatileImpl class we want (OUStringHash is in class OUString, fortunately).

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static unordered_map<OUString,ExampleAddInResult *,OUStringHash> aResults;

and since it is static, we need to also declare it outside the definition

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unordered_map<OUString,ExampleAddInResult *,OUStringHash> VolatileImpl::aResults;

The getCounter function itself is then

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Reference<XVolatileResult> SAL_CALL VolatileImpl::getCounter( OUString const & aName)
		throw (RuntimeException)
{
	ExampleAddInResult *aResult;
	Reference<XVolatileResult> vResult;
	MyResultListener *aListener = new MyResultListener;
	Reference<XResultListener> xListener = static_cast< XResultListener * > ( aListener );
	
	if(aResults.count(aName) == 0) {
		aResult = new ExampleAddInResult(aName);
		aResults[aName] = aResult;
	} else {
		aResult = aResults[aName];
	}
	vResult = static_cast< XVolatileResult * > (aResult);
	return vResult;
}

It seems addResultListener is called automatically, and it is a mistake I made to try and call it explicitly, but a MyResultListener must be declared within the function.

Now what happens when we enter in a cell ("x" is an arbitrary string)

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=GETCOUNTER("x")

The cell just displays

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x 0

based on the ResultEvent.Value from the getResult() method, but it will increment whenever the result objects IncrementValue method is called

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	void incrementValue() {
		long i;
		++nValue;
		com::sun::star::sheet::ResultEvent aEvent = getResult();
		for(i = 0;i < myListeners.size(); i++) 
			myListeners[i]->modified(aEvent);
		
    }
	

So I'm making another function to do that

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OUString SAL_CALL VolatileImpl::IncrementCounter( OUString const & aName)
		throw (RuntimeException)
{
	
	ExampleAddInResult *aResult;

	if(aResults.count(aName) == 0) {
		return aName + OUString(RTL_CONSTASCII_USTRINGPARAM(" is null."));
	} else {
		aResult = aResults[aName];
		aResult->incrementValue();
		return aName + OUString(RTL_CONSTASCII_USTRINGPARAM(" incremented."));
	}
}

So if we put in a cell

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=INCREMENTCOUNTER("x")

the GETCOUNTER("x") cell will increment x 1, x 2, x 3, etc. each time the INCREMENTCOUNTER is recalculated. Note the the INCREMENTCOUNTER can be on a different sheet and even in a different document.

It also works if called from somewhere else. So if we put in Basic

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Sub Main
	IncIt("x")
End Sub


Sub IncIt(aName As String)
	Dim svc As Object
	
	svc = createUnoService("com.sun.star.sheet.FunctionAccess")
	svc.callFunction("com.volresult.my_volatile_implementation.Volatile.IncrementCounter",Array(aName))
End Sub

the GETCOUNTER("x") cell will increment whenever Main is run.

This whole mechanism is intended to update data in real time, of course, and I'm just now starting to look into that part. I'll probably go back to Python for that at first, since I think Python has facilities for reading web data that are much easier to implement than any such thing in c++.

[saleem145]

Can a volatile function return a 2 dimensional array of data??

Saleem

[karolus]

Hallo

Can a volatile function return a 2 dimensional array of data??

Saleem

Yes!

[Charlie Young]

Just to c0nfirm this.

Modify the getResult() function from above:

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com::sun::star::sheet::ResultEvent ExampleAddInResult::getResult()
{
	com::sun::star::sheet::ResultEvent aEvent;
	Sequence<Sequence<Any>> ResultArray(1);
	ResultArray[0] = Sequence<Any>(2);
	ResultArray[0][0] <<= aName;
	ResultArray[0][1] <<= (sal_Int32) nValue;
	aEvent.Value <<= ResultArray;
	Reference< XInterface > x( static_cast< lang::XTypeProvider * >( this ) );
	aEvent.Source = x;
	return aEvent;
}

Then enter getCounter() as an array formula (Ctrl-Shift-Enter), and the object name and counter are returned in two adjacent cells on a row.

It is worth noting that this only requires modifying the c++, and no changes need to be made to the .idl or the CalcAddin.xcu.

I'll leave it as an exercise to return the entries in a column.

It should be obvious how to extend this to larger arrays, but one consideration might be: is it necessary that the array always have the same dimensions? I'm guessing yes, since my experience is that array formulas are frozen in size after initial entry.

[Villeroy]

I'll leave it as an exercise to return the entries in a column.

=TRANSPOSE(GETCOUNTER("x"))

[Charlie Young]

=TRANSPOSE(GETCOUNTER("x"))

Got me , that works.

(Of course changing the source code is also rather trivial.)