[Paraview-developers] Fwd: How to plug into paraview his own writer ?

[houssen]

I followed 2 writer examples (cpp, hpp) : Xdmf writer and OpenFOAM 
writer. Complexity is high, still difficult to extract basic needs out 
of them.

Question 1 : how to write myWriter.xml ?

1.1. seems I must set <InputProperty command="SetInputConnection" 
name="Input"> in myWriter.xml. Does this means I will also have to 
implement myWriter::SetInputConnection ?

1.2. seems I must set <StringVectorProperty name="FileName" 
command="SetFileName"> in myWriter.xml. Does this means I will also have 
to implement myWriter::SetFileName ?

I am correct ?

Question 2 : how to implement a vtk object ? From here 
http://www.vtk.org/Wiki/VTK/Examples/Developers/vtkObject, it seems that

2.1. in myWriter.cpp, I need to have :
#include "vtkObjectFactory.h" // vtkStandardNewMacro
vtkStandardNewMacro ( myWriter ); // use vtkStandardNewMacro : 1 only 
allowed constructor, omit the copy constructor and operator=
+ suppress copy constructor and operator=

2.2 in myWriter.hpp, I need to derive from a vtkObject this way (like 
XdmfWriter.cpp does) :
class myWriter : public vtkDataObjectAlgorithm {
   public:
     static myWriter * New (); // Needed to be plugged into paraview
     vtkTypeMacro ( myWriter, vtkDataObjectAlgorithm ); // Needed to be 
plugged into paraview
+ suppress copy constructor and operator=

Am I correct ?

Question 3 : in myWriter.cpp, on which method I am supposed to be 
called back (to get focus back) when I click the "save data" button ? 
Here, how can I get data to be saved (data that I can see in paraview 
viewer before to click the save button - I guess this data will be a 
vtk*).

Finally, myWriter.xml seems OK. myWriter.*pp compile OK. Paraview finds 
myWriter.xml at run time (exporting PV_PLUGIN_PATH) and loads 
libmywriter.so without problem. I see the writer in the "save data" GUI 
(drop down list with different save formats). I save with myWriter, I 
get a (basic) GUI with file name only (no extra parameter) : I crash 
when I click "OK, save" with this error message :
ERROR: In 
/.../ParaView-v4.3.1-source/ParaViewCore/ServerImplementation/Core/vtkSIProxy.cxx, 
line 307
vtkSIWriterProxy (0x30143d0): Failed to create myWriter. Aborting for 
debugging purposes.

vtkSIWriterProxy does this at line 303 :
vtkObjectBase* obj = this->Interpreter->NewInstance(className);
but obj is NULL.

I get obj is NULL because I missed something in myWriter implementation 
: what did I miss ?

Can somebody help ? Or even get me some clue ?

FH

-------- Message original --------
Objet: How to plug into paraview his own writer ?
Date: 2015-06-12 15:54
De: houssen <houssen at imap.ipgp.fr>
À: <paraview at paraview.org>

I followed 2 tutorials 
(http://www.itk.org/Wiki/ParaView/Plugin_HowTo#Writing_Plugins, 
http://www.kitware.com/media/html/WritingAParaViewReaderPlug-in.html) 
but I feel like I missed some steps : this is not working.

I need to "catch" data (I can see in 2D/3D paraview viewer) to write 
them into a specific file format. I am looking for the minimal 
(simplest) way to do this : the only writer input is the file name, then 
I would like to understand how to "get data from" paraview (from inside 
a vtk object I guess ?), then I just will have to do the easy part which 
is to write data to a specific format.

My understanding is that, first I need a CMakeLists.txt like :
~> more CMakeLists.txt
FIND_PACKAGE ( ParaView REQUIRED )
INCLUDE ( ${PARAVIEW_USE_FILE} )
ADD_PARAVIEW_PLUGIN ( myWriter "1.0" SERVER_MANAGER_XML myWriter.xml
SERVER_MANAGER_SOURCES myWriter.cpp )

In the same directory, I need a (minimal) myWriter.xml file that looks
like :
~> more myWrite.xml
  <ServerManagerConfiguration>
  <ProxyGroup name="WRITERS">
  <SourceProxy name="MYWRITER" class="MYWRITER" label="my writer">
  <Documentation short_help="my own writer"/>
  <InputProperty>
  <StringVectorProperty name="FileName" command="SETFILENAME" 
number_of_elements="1"/>
  </InputProperty>
  <Hints>
  <WriterFactory extensions="mw" file_description="my written file"/>
  </Hints>
  </SourceProxy>
  </ProxyGroup>
</ServerManagerConfiguration>
My understanding is that somehow the xml subscribes my for a specific 
callback I am called back on the "save data" button is cliked in the 
GUI.

Still, in this same directory, I have myWriter.cpp and myWriter.hpp :
how to implement them ?
1. The myWriter class must define and implement a SetFileName method 
because of the <StringVectorProperty> xml tag in myWriter.xml : right ? 
wrong ?
    This is the file name (including file path) one sets in the GUI : 
right ? wrong ?
2. myWriter is supposed to derive from another class : which one ? 
where to find it ?
3. How the myWriter implementation will "catch" data in paraview ? 
Which method to override / re-implement ?
    When I am called from paraview (triggered by the click on "save 
data" button), I guess I am called on a specific method 
"myWriter::cbMethod ( vtkXXX * pDataInParaviewViewer )"
   What is this method ?

Also, at this step, I export 
PV_PLUGIN_PATH=/mnt/users/houssen/Documents/solve-rel/paraview. When I 
run paraview and use the "save data" button I get this :
Generic Warning: In 
/.../Programs/ParaView/ParaView-v4.3.1-source/ParaViewCore/ServerManager/Core/vtkSMWriterFactory.cxx, 
line 135
writers : myWriter has no input property.
... But I have an <InputProperty> tag in the xml : what's wrong ?

Can somebody help me on this ?

Franck

Note : I run Ubuntu and paraview-4.3