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Fix documentation glitches (#1337)
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* Fix sphinx extensions in conf.py and requirements.txt

Signed-off-by: Cary Phillips <cary@ilm.com>

* Fix documentation glitches

* Rename Overview to OpenEXR, so the homepage browser tab says OpenEXR
* Move Porting Guide and Symbol Visibility under Concepts

Signed-off-by: Cary Phillips <cary@ilm.com>

---------

Signed-off-by: Cary Phillips <cary@ilm.com>
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cary-ilm committed Mar 5, 2023
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2 changes: 0 additions & 2 deletions docs/API.rst
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Expand Up @@ -14,8 +14,6 @@ The OpenEXR API
HelloWorld
ReadingAndWritingImageFiles
OpenEXRCoreAPI
PortingGuide
SymbolVisibility

* :ref:`genindex`

127 changes: 79 additions & 48 deletions docs/SymbolVisibility.rst
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Expand Up @@ -24,14 +24,14 @@ mechanics, follow the same rules between gcc, clang, and
msvc. However, types have richer information than they do in C. So,
unless extra work is done, concepts for RTTI like the typeinfo and the
vtable for virtual classes will be hidden, and not visible. These are
referred to as "vague" linkage objects in some discussions.
referred to as "vague" linkage objects in some discussions.

It is with the "vague" linkage objects where different properties
arise. For example, if you have a template, it is happily instantiated
in multiple compile units. If the typeinfo is hidden for one library,
then this may cause things like dynamic_cast to fail because then the
same typeinfo is not used, and even though one might think that
ImfAttribute<Imath::Box2i> are the same in two places, because they
``ImfAttribute<Imath::Box2i>`` are the same in two places, because they
are instantiated in separate places, they may be considered different
types. To compound the issue, there are different rules for this in
different implementations. For example, a default gcc under linux
Expand Down Expand Up @@ -63,61 +63,92 @@ it also exports the types for the member types as well, which is not
desired, so these are marked as N/A even though the compiler does
allow that to happen.


+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| C++ vs Compiler | MSVC | mingw | gcc | clang |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| function | ``dllexport/dllimport`` | ``dllexport/dllimport`` | ``visibility("default")`` | ``visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| hide a function | N/A | N/A | ``visibility("hidden")`` | ``visibility("hidden")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| ``class(typeinfo)`` | N/A | N/A | ``visibility("default")`` | ``visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| template class | N/A | N/A | ``visibility("default")`` | ``type_visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| template data | N/A | N/A | ``visibility("default")`` | ``visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| class template<br> instantiation | ``dllexport/dllimport`` | N/A | N/A | ``visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| enum | N/A | N/A | auto unhides (N/A) | ``type_visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
| extern template | N/A | ``dllexport/dllimport`` | ``visibility("default")`` | ``visibility("default")`` |
+----------------------------------+-------------------------+-------------------------+---------------------------+--------------------------------+
.. list-table::
:header-rows: 1
:align: left

* - C++ vs Compiler
- MSVC
- mingw
- gcc
- clang
* - function
- ``dllexport/dllimport``
- ``dllexport/dllimport``
- ``visibility("default")``
- ``visibility("default")``
* - hide a function
- N/A
- N/A
- ``visibility("hidden")``
- ``visibility("hidden")``
* - ``class(typeinfo)``
- N/A
- N/A
- ``visibility("default")``
- ``visibility("default")``
* - template class
- N/A
- N/A
- ``visibility("default")``
- ``type_visibility("default")``
* - template data
- N/A
- N/A
- ``visibility("default")``
- ``visibility("default")``
* - class template instantiation
- ``dllexport/dllimport``
- N/A
- N/A
- ``visibility("default")``
* - enum
- N/A
- N/A
- auto unhides (N/A)
- ``type_visibility("default")``
* - extern template
- N/A
- ``dllexport/dllimport``
- ``visibility("default")``
- ``visibility("default")``

With this matrix in mind, we can see the maximal set of macros we need to
provide throughout the code. *NB*: This does not mean that we need to
declare all of these, just that they might be needed. `XXX` should be
substituted for the particular library name being compiled.

+----------------------------------+------------------------------------------------------------------+
| macro name | purpose |
+----------------------------------+------------------------------------------------------------------+
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT`` | one of export or import for windows, visibility for others |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT_TYPE`` | for declaring a class / struct as public (for typeinfo / vtable) |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_HIDDEN`` | used to explicitly hide, especially members of types |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT_TEMPLATE_TYPE`` | stating the template type should be visible |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT_EXTERN_TEMPLATE`` | exporting template types (i.e. extern side of extern template) |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT_TEMPLATE_INSTANCE`` | exporting specific template instantiations (in cpp code) |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT_TEMPLATE_DATA`` | exporting templated data blocks |
+----------------------------------+------------------------------------------------------------------+
| ``XXX_EXPORT_ENUM`` | exporting enum types |
+----------------------------------+------------------------------------------------------------------+
declare all of these, just that they might be needed. ``XXX`` should be
substituted for the particular library name being compiled
(``OPENEXR``, ``OPENEXRUTIL``, ``OPENEXRCORE``, ``IEX``,
``ILMTHREAD``, ``IMATH``).

.. list-table::
:header-rows: 1
:align: left

* - macro name
- purpose
* - ``XXX_EXPORT``
- one of export or import for windows, visibility for others
* - ``XXX_EXPORT_TYPE``
- for declaring a class / struct as public (for typeinfo / vtable)
* - ``XXX_HIDDEN``
- used to explicitly hide, especially members of types
* - ``XXX_EXPORT_TEMPLATE_TYPE``
- stating the template type should be visible
* - ``XXX_EXPORT_EXTERN_TEMPLATE``
- exporting template types (i.e. extern side of extern template)
* - ``XXX_EXPORT_TEMPLATE_INSTANCE``
- exporting specific template instantiations (in cpp code)
* - ``XXX_EXPORT_TEMPLATE_DATA``
- exporting templated data blocks
* - ``XXX_EXPORT_ENUM``
- exporting enum types

For a new library, the preference might be to call ``XXX_EXPORT``
something like ``XXX_FUNC``, and rename things such as ``XXX_EXPORT_TYPE``
to ``XXX_TYPE`` for simplicity. However, historically, OpenEXR has used
the ``_EXPORT`` tag, and so that is preserved for consistency.

References
==========
---------

* LLVM libc++ visibility macros: https://libcxx.llvm.org/docs/DesignDocs/VisibilityMacros.html

Expand Down
2 changes: 2 additions & 0 deletions docs/concepts.rst
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Expand Up @@ -17,3 +17,5 @@ OpenEXR Concepts
InterpretingDeepPixels
TheoryDeepPixels
OpenEXRFileLayout
PortingGuide
SymbolVisibility
17 changes: 10 additions & 7 deletions docs/index.rst
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Expand Up @@ -2,13 +2,13 @@
SPDX-License-Identifier: BSD-3-Clause
Copyright Contributors to the OpenEXR Project.
.. _Overview:
.. _OpenEXR:

Overview
########
OpenEXR
#######

.. toctree::
:caption: Overview
:caption: OpenEXR
:maxdepth: 1

.. sidebar::
Expand Down Expand Up @@ -38,7 +38,9 @@ The OpenEXR project includes `Imath <https://imath.readthedocs.io>`_,
a basic, light-weight, and efficient C++ representation of 2D and 3D
vectors and matrices and other simple but useful mathematical objects,
functions, and data types common in computer graphics applications,
including the “half” 16-bit floating-point type.
including the `half
<https://imath.readthedocs.io/en/latest/classes/half.html>`_ 16-bit
floating-point type.

Imath also includes optional python bindings for all types and
functions, including optimized implementations of vector and matrix
Expand Down Expand Up @@ -76,9 +78,10 @@ Community

* **Contribute a Fix, Feature, or Improvement:**

- Read the `Contribution guidelines
- Read the `Contribution Guidelines
<https://github.com/AcademySoftwareFoundation/openexr/blob/main/CONTRIBUTING.md>`_
and `Code of Conduct <https://github.com/AcademySoftwareFoundation/openexr/blob/main/CODE_OF_CONDUCT.md>`_
and `Code of Conduct
<https://github.com/AcademySoftwareFoundation/openexr/blob/main/CODE_OF_CONDUCT.md>`_

- Sign the `Contributor License Agreement
<https://contributor.easycla.lfx.linuxfoundation.org/#/cla/project/2e8710cb-e379-4116-a9ba-964f83618cc5/user/564e571e-12d7-4857-abd4-898939accdd7>`_
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