GateImageBox.h includes Geant4 private header, breaking builds without private headers installed

[jakeforster]

Since the last release (10.0.2), the file GateImageBox.h was added which includes a private/internal header from Geant4:

opengate/core/opengate_core/opengate_lib/GateImageBox.h

Line 31 in 78e5494

#include "private/G4OpenGLSceneHandler.hh"

Can this dependency be avoided or made optional? Unless I'm mistaken, private headers are not part of the public API and are not usually installed.

[tbaudier]

Hello @jakeforster

I do not understand well your remark when you mention "are not part of the public API and are not usually installed." because on my side, when I compiled G4 with default option, it's ok.

For the moment, there is no way to made it optional. A solution could be to avoid to compile G4 with visu options and by default the GateImageBox class will not be taken into account. But the Qt visualisation will not be available anymore

Regards

[jakeforster]

Hi @tbaudier, thanks for taking a look at this.

Does it perhaps work for you (and CI) because you are including Geant4 from its build tree or source tree instead of from the install prefix? These headers are declared as private and therefore I don't think they are installed in a standard Geant4 installation.

G4OpenGLSceneHandler.hh is defined as a private header here:

# Define the Geant4 Module.
# The base set of G4OpenGL classes are all private because fundamentally they
# are never exposed outside of the category.
geant4_add_module(G4OpenGL
  PRIVATE_HEADERS 
    G4gl2ps.hh
    G4OpenGL.hh
    G4OpenGLFontBaseStore.hh
    G4OpenGLImmediateViewer.hh
    G4OpenGLImmediateSceneHandler.hh
    G4OpenGLStoredViewer.hh
    G4OpenGLStoredSceneHandler.hh
    G4OpenGLSceneHandler.hh
    G4OpenGLSceneHandler.icc
    G4OpenGLTransform3D.hh
    G4OpenGLViewer.hh
    G4OpenGLViewerMessenger.hh
    G4VisFeaturesOfOpenGL.hh
  SOURCES
    G4OpenGLImmediateViewer.cc
    G4OpenGLImmediateSceneHandler.cc
    G4OpenGLViewer.cc
    G4OpenGLStoredViewer.cc
    G4OpenGLStoredSceneHandler.cc
    G4OpenGLFontBaseStore.cc
    G4OpenGLSceneHandler.cc
    G4OpenGLViewerMessenger.cc
    G4OpenGLTransform3D.cc
    G4VisFeaturesOfOpenGL.cc
    G4gl2ps.cc) 

The macro geant4_add_module is defined here and I've pasted the docstring below:

# .. cmake:command:: geant4_add_module
#
#   .. code-block:: cmake
#
#     geant4_add_module(<name>
#                       PUBLIC_HEADERS header1 [header2 ...]
#                       PRIVATE_HEADERS header1 [header2 ..]
#                       [SOURCES source1 [source2 ...]])
#
#   Add a Geant4 module called ``<name>`` to the project, composed
#   of the source files listed in the ``PUBLIC_HEADERS``, ``PRIVATE_HEADERS``, 
#   and ``SOURCES`` arguments. The ``<name>`` must be unique within the project.
#   The directory in which the module is added (i.e. ``CMAKE_CURRENT_LIST_DIR``
#   for the CMake script in which ``geant4_add_module`` is called) must contain:
#
#   * An ``include`` subdirectory for the public headers
#   * A ``include/private`` subdirectory for the private headers
#   * A ``src`` subdirectory for source files if the module provides these
#
#   Any module with only ``PUBLIC_HEADERS`` has its ``IS_INTERFACE`` property
#   set to ``TRUE``. This is for downstream use in composing and building end
#   targets appropriately.
#
#   The ``PUBLIC_HEADERS`` argument must list the headers comprising the
#   public interface of the module. If a header is supplied as a relative path,
#   this is interpreted as being relative to the ``include`` subdirectory of the module.
#   Absolute paths may also be supplied, e.g. if headers are generated by the project.
#
#   The ``PRIVATE_HEADERS`` argument must list the headers comprising any
#   interfaces that are implementation details of the module. If a header is supplied 
#   as a relative path, this is interpreted as being relative to the ``include/private`` 
#   subdirectory of the module. Absolute paths may also be supplied, e.g. if headers
#   are generated by the project. 
#
#   The ``SOURCES`` argument should list any source files for the module.
#   If a source is is supplied as a relative path, this is interpreted as being
#   relative to the ``src`` subdirectory of the module. Absolute paths may
#   also be supplied, e.g. if sources are generated by the project.

In particular:

#   The ``PUBLIC_HEADERS`` argument must list the headers comprising the
#   public interface of the module.

I think this indicates that private headers are not part of the public API, and therefore it makes sense that they would not be installed in a standard Geant4 installation. If that is the case, for GATE to support using an external Geant4 installation, it must limit itself to Geant4's public interface. (There might be other reasons to not rely on private headers too, like lack of stability guarantees.) Fortunately this appears to be the only instance where GATE is using a private header, and it was introduced after the last release.

Thanks again.
Jake

[tbaudier]

Good point, you're right. The private header are not installed ( release-note v11.2 )

The use of G4OpenGLSceneHandler is necessary to display image as geometry in the Qt GUI

opengate/core/opengate_core/opengate_lib/GateImageBox.cpp

Line 72 in 78e5494

void GateImageBox::DescribeYourselfTo(G4OpenGLSceneHandler &scene) const {

with the class GateImageBox. This class inherits from G4Box. Do you know if there is another way to do it?

Maybe I'm wrong but I'm not sure it's a problem for the user. For regular users, they will use the wheel from pypi. So the G4 library is included inside. For developper users, usually they compile G4 by themself to be able to compile opengate. I'm not sure there is a lot of developper who uses the installed version of G4.