[vtkusers] Forward declaration of Foo enough for vtkNew<Foo> declaration?

[Shawn Waldon]

Hi Elvis,

The problem is this:  Declaring vtkNew<Foo> should be fine when Foo is
forward declared.  But when the vtkNew<Foo> is deleted in your destructor,
the vtkNew<Foo>'s destructor needs to call Foo->Delete().  So at that point
it needs the full definition of Foo.  In your example, if you declare your
class's destructor and implement it as {} (use the default) in an
implementation file where Foo's header is included this should work.  One
of my projects uses vtkNew this way.

HTH,
Shawn

On Wed, Aug 10, 2016 at 8:39 AM, Elvis Stansvik <
elvis.stansvik at orexplore.com> wrote:

> 2016-08-10 14:32 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>
>> Hi,
>>
>> The overview at
>>
>>     https://blog.kitware.com/a-tour-of-vtk-pointer-classes/
>>
>> seems to suggest that forward declaration of a class Foo should be enough
>> to be able to declare a vtkNew<Foo> (e.g. see how vtkTable is used in the
>> code example under "Use of Classes").
>>
>> But when I try e.g:
>>
>> class vtkCompositeTransferFunctionItem;
>> ...
>> vtkNew<vtkCompositeTransferFunctionItem> m_functionsItem;
>>
>> I get
>>
>>     error: invalid use of incomplete type ‘class
>> vtkCompositeTransferFunctionItem’
>>
>> Do I really need to include vtkCompositeTransferFunctionItem.h to
>> declare a vtkNew<vtkCompositeTransferFunctionItem> ?
>>
>
> To show more of the context where I'm trying this:
>
> #pragma once
>
> #include "VTKWidget.h"
>
> #include <QObject>
> #include <Qt>
>
> #include <vtkNew.h>
>
> #include <vtkChartXY.h>
> #include <vtkContextView.h>
> #include <vtkCompositeControlPointsItem.h>
> #include <vtkCompositeTransferFunctionItem.h>
>
> class QWidget;
>
> class vtkColorTransferFunction;
> // Apparently I can't just forward declare these.
> //class vtkChartXY;
> //class vtkCompositeTransferFunctionItem;
> //class vtkCompositeControlPointsItem;
> //class vtkContextView;
> class vtkPiecewiseFunction;
>
> class CompositeTransferFunctionEditor : public VTKWidget
> {
>     Q_OBJECT
>
> public:
>     enum Mode {
>         EditColor,
>         EditOpacity
>     };
>     Q_ENUM(Mode)
>
> public:
>     CompositeTransferFunctionEditor(vtkColorTransferFunction
> *colorFunction,
>                                     vtkPiecewiseFunction *opacityFunction,
>                                     Mode mode = EditColor,
>                                     QWidget *parent = 0,
>                                     Qt::WindowFlags flags =
> Qt::WindowFlags());
>
>     void setColorFunction(vtkColorTransferFunction *colorFunction);
>     void setOpacityFunction(vtkPiecewiseFunction *opacityFunction);
>
> signals:
>     void functionsModified();
>
> private:
>     void editColorPoint();
>
> private:
>     vtkNew<vtkCompositeTransferFunctionItem> m_functionsItem;
>     vtkNew<vtkCompositeControlPointsItem> m_pointsItem;
>     vtkNew<vtkChartXY> m_chart;
>     vtkNew<vtkContextView> m_contextView;
> };
>
> I had hoped I would only have to forward declare the types used in the
> instantiations of vtkNew here, not include the full headers.
>
> Elvis
>
>
>> Thanks,
>> Elvis
>>
>
>
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