magnum/doc/platforms-macos.dox

/*
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              Vladimír Vondruš <mosra@centrum.cz>

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namespace Magnum {

/** @page platforms-macos macOS
@brief Tips and tricks for macOS

@tableofcontents
@m_footernavigation

@m_keyword{Apple macOS,,}

@todoc code coverage

See also @ref platforms-ios.

@section platforms-macos-bundle Bundle creation

While graphical applications *can* run "as is", directly from the compiled
executable, it's not possible to set various crucial properties of the app
such as @ref platforms-macos-hidpi "HiDPI" support --- for that you need to
create a bundle, specifying its options through a `*.plist` file. If you use
CMake, it provides [a builtin file](https://cmake.org/cmake/help/latest/prop_tgt/MACOSX_BUNDLE_INFO_PLIST.html)
with a few options and you can use it like this:

@code{.cmake}
add_executable(my-application main.cpp)
# ...
if(CORRADE_TARGET_APPLE)
    set_target_properties(my-application PROPERTIES
        MACOSX_BUNDLE ON
        MACOSX_BUNDLE_BUNDLE_NAME "My Application"
        MACOSX_BUNDLE_BUNDLE_IDENTIFIER "cz.mosra.magnum.my-application")
endif()
@endcode

The builtin file doesn't include all possible properties, however it's possible
to supply your own. A minimal file can look like this:

@code{.xml-jinja}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>CFBundleDevelopmentRegion</key>
  <string>en-US</string>
  <key>CFBundleExecutable</key>
  <string>${MACOSX_BUNDLE_EXECUTABLE_NAME}</string>
  <key>CFBundleIdentifier</key>
  <string>{{ package }}</string>
  <key>CFBundleInfoDictionaryVersion</key>
  <string>6.0</string>
  <key>CFBundleName</key>
  <string>{{ app_name }}</string>
  <key>CFBundlePackageType</key>
  <string>APPL</string>
</dict>
</plist>
@endcode

Replace @cb{.jinja} {{ package }} @ce with Java-like package name for your app
(in this case it could be e.g. @cpp "cz.mosra.magnum.my_application" @ce, for
example), @cb{.jinja} {{ app_name }} @ce with human-readable app name that's
displayed in the system (so e.g. @cpp "My Application" @ce). If you name it
`MacOSXBundleInfo.plist.in`, it can be supplied to the bundle like below. The
@cb{.cmake} ${MACOSX_BUNDLE_EXECUTABLE_NAME} @ce will get automatically
replaced with the target executable name.

@code{.cmake}
if(CORRADE_TARGET_APPLE)
    set_target_properties(my-application PROPERTIES
        MACOSX_BUNDLE ON
        MACOSX_BUNDLE_INFO_PLIST ${CMAKE_CURRENT_SOURCE_DIR}/MacOSXBundleInfo.plist.in)
endif()
@endcode

See [the official Apple Property List file documentation](https://developer.apple.com/library/content/documentation/General/Reference/InfoPlistKeyReference/Articles/AboutInformationPropertyListFiles.html)
for information about all options.

If you don't use CMake, these options can be set directly through Xcode UI, for
example.

@subsection platforms-macos-bundle-dylibs Bundling dylibs

If your application relies on dylibs (such as `libGLESv2.dylib` /
`libEGL.dylib` for @ref platforms-gl-es-angle "ANGLE"), there's a few extra
steps compared to static libraries to get them working. First, these have to be
put into the `Frameworks/` directory inside the bundle --- for example like
below if you have them referenced with a CMake project. Additionally, the
files may need to get signed when copied:

@code{.cmake}
set_source_files_properties(libGLESv2.dylib libEGL.dylib PROPERTIES
    MACOSX_PACKAGE_LOCATION Frameworks
    XCODE_FILE_ATTRIBUTES CodeSignOnCopy)
@endcode

Then, the `*.dylib` files need to have their install name changed to contan a
RPATH entry, so the executable linking to them will know it has to look for
them in the RPATH. For 3rd party `*.dylib` files it can be done with the
following command, dynamic libraries built directly by CMake
[should have this already set](https://cmake.org/cmake/help/latest/prop_tgt/MACOSX_RPATH.html).

@code{.sh}
install_name_tool -id "@rpath/libGLESv2.dylib" libGLESv2.dylib
install_name_tool -id "@rpath/libEGL.dylib" libEGL.dylib
@endcode

Finally, the application executable needs to have the RPATH pointed to the
framework location:

@code{.sh}
set_target_properties(my-application PROPERTIES
    INSTALL_RPATH "@executable_path/../Frameworks")
@endcode

@section platforms-macos-hidpi HiDPI (Retina) support

macOS and iOS is the only platform where HiDPI support of an app can't be
advertised programmatically. According to various sources, this capability is
enabled by default on macOS 10.15+ and iOS 13+, for older versions you need to
supply a custom `*.plist` file with `NSHighResolutionCapable` enabled:

@code{.xml}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  ...
  <key>NSHighResolutionCapable</key>
  <true/>
</dict>
</plist>
@endcode

If you are using CMake, you can use the @ref platforms-macos-bundle "method described above"
to create a bundle with given file. Also note that this property is already
included in CMake's builtin `Info.plist` on [version 3.9 and newer](https://gitlab.kitware.com/cmake/cmake/merge_requests/682).

@section platforms-macos-clang-version-mapping Clang version mapping

Apple Clang has a different versioning scheme from upstream Clang, making it
hard to know which Clang version corresponds to which Apple Clang version.
Wikipedia has a [handy version mapping table](https://en.wikipedia.org/wiki/Xcode#Toolchain_versions).

CMake exposes Apple Clang as `AppleClang`, so a complete check for e.g.
upstream version 5 needs to look like this:

@code{.cmake}
if((CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND NOT
    CMAKE_CXX_COMPILER_VERSION VERSION_LESS "5.0") OR
   (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" AND NOT
    CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9.3"))
    # Code requiring Clang 5 and newer
endif()
@endcode

@note CMake supports `VERSION_GREATER_EQUAL` in the @cb{.cmake} if() @ce
    statement only [since version 3.7](https://cmake.org/cmake/help/latest/release/3.7.html#commands),
    use a negated `VERSION_LESS` like above in older versions.

@see @ref platforms-windows-msvc-version-mapping

@section platforms-macos-opengl-best-practices Best practices

Official Apple documentation:

-   [Best Practices for Working with Vertex Data](https://developer.apple.com/library/mac/#documentation/graphicsimaging/Conceptual/OpenGL-MacProgGuide/opengl_vertexdata/opengl_vertexdata.html)
-   [Best Practices for Working with Texture Data](https://developer.apple.com/library/mac/#documentation/graphicsimaging/Conceptual/OpenGL-MacProgGuide/opengl_texturedata/opengl_texturedata.html)

@section platforms-macos-travis Setting up macOS build on Travis CI

A lot of Travis features is shared between Linux and macOS, see
@ref platforms-linux-travis for more information.

In general, a macOS build is done by adding the following to your `.travis.yml`
matrix build. See [the official documentation](https://docs.travis-ci.com/user/reference/osx/)
for more information.

@code{.yml}
matrix:
  include:
  - language: cpp
    os: osx
    compiler: clang
@endcode

Most of the build setup can be shared with Linux, as both systems have roughly
the same set of packages. For installing dependencies there's no builtin way,
but you can use Homebrew. Be aware that calling for example
@cb{.sh} brew install ninja @ce by default causes Homebrew to update itself
first. That currently (March 2018) takes almost two minutes. It's possible to
skip the update by setting an environment variable as shown below, however this
might fail in case you need a very recent version of a package.

@code{.sh}
HOMEBREW_NO_AUTO_UPDATE=1 brew install ninja
@endcode

@section platforms-macos-troubleshooting Troubleshooting

@subsection platforms-macos-troubleshooting-build-mysteriously-fails Build mysteriously fails due to some &lt;cmath&gt; errors

Happening usually after a system or Xcode upgrade, builds can start failing
with errors like below. The exact reasons are unclear, can vary and happen only
in certain cases (for example a manual build works but Homebrew package install
doesn't).

@m_class{m-console-wrap}

@code{.ansi}
In file included from ../src/MagnumPlugins/PngImageConverter/PngImageConverter.cpp:42:
In file included from /usr/local/include/Magnum/ImageView.h:35:
In file included from /usr/local/include/Magnum/PixelStorage.h:36:
In file included from /usr/local/include/Magnum/Math/Vector3.h:32:
In file included from /usr/local/include/Magnum/Math/Vector2.h:32:
In file included from /usr/local/include/Magnum/Math/Vector.h:37:
In file included from /usr/local/include/Corrade/Utility/StlMath.h:75:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:317:9: error: no member named 'signbit' in the global namespace
using ::signbit;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:318:9: error: no member named 'fpclassify' in the global namespace
using ::fpclassify;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:319:9: error: no member named 'isfinite' in the global namespace; did you mean 'finite'?
using ::isfinite;
      ~~^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk/usr/include/math.h:752:12: note: 'finite' declared here
extern int finite(double)
           ^
@endcode

In the above case it's because @ref Trade::PngImageConverter "PngImageConverter"
(or @ref Trade::PngImporter "PngImporter") uses libPNG, which depends on zlib.
Zlib, along with curl and few others are the only libraries shipped directly
with macOS, and that's the core of the problem. Here zlib got errorneously
found in a different SDK than the remaining dependencies, causing two mutually
incompatible include directories from a 11.0 and 10.15 SDK used together, as
can be seen in the clang invocation (which gets displayed by `ninja` on failure
or can be retreived from Homebrew logs):

@m_class{m-console-wrap}

@code{.ansi}
clang++ … -I/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk/usr/include … -o CMakeFiles/PngImageConverter.dir/PngImageConverter.cpp.o -c ../src/MagnumPlugins/PngImageConverter/PngImageConverter.cpp -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk --sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk -isystem/usr/local/include
@endcode

A magic incantation that should remove the curse, often suggested by Homebrew
itself, is the following:

@code{.sh}
sudo rm -rf /Library/Developer/CommandLineTools
sudo xcode-select --install
@endcode

@section platforms-macos-vulkan Vulkan on macOS

Vulkan on macOS is implemented on top of Metal, and there are two possible
ways:

-   Using [MoltenVK](https://github.com/KhronosGroup/MoltenVK) directly. The
    library can supplement a Vulkan loader as well, which means you don't need
    two libraries, however this way you lose the possibility to have multiple
    devices (for example a SwiftShader software rendering). MoltenVK is
    directly available in Homebrew as `molten-vk`.
-   Using [Vulkan Loader](https://github.com/KhronosGroup/Vulkan-Loader)
    together with MoltenVK and possibly other device implementations. That way
    you'll get the benefits of a standard loader and device selection. The
    loader isn't available in Homebrew so you need to either install the whole
    several-hunred-megabyte SDK or [build it from source](https://github.com/KhronosGroup/Vulkan-Loader/blob/master/BUILD.md#building-on-macos).

Magnum's own [FindVulkan.cmake](https://github.com/mosra/magnum/blob/master/modules/FindVulkan.cmake)
will look for the Vulkan Loader first and if not found, falls back to searching
for MoltenVK.

@section platforms-macos-gl OpenGL on macOS

With Apple decision to focus on Metal, macOS OpenGL support is stuck on version
4.1 (i.e., two versions before compute shaders are available). Moreover, OpenGL
is deprecated since macOS 10.14. If you don't want to rely on the deprecated
OpenGL driver, you have an option to use
@ref platforms-macos-vulkan "Vulkan as shown above", go with ANGLE to translate
OpenGL to Metal (details below), or go with Mesa Zink to translate OpenGL to
Vulkan.

With the deprecated macOS drivers, these are the known issues:

-   @ref GL::AbstractShaderProgram::validate() expects that the shader has a
    properly configured framebuffer bound along with proper @ref GL::Renderer
    setup. That is often hard to achieve, so the function cannot be portably
    used for shader validity testing.
-   `GL_TIMESTAMP` used by @ref GL::TimeQuery::timestamp() is not implemented
    on macOS and gives zero results.

@subsection platforms-macos-gl-angle Using ANGLE to translate OpenGL to Metal

@todoc cmake options to switch to GLES/EGL, mention getting the binaries from browser installs
@todoc steps for building angle from scratch?
@todoc reference this from the iOS guide

See also @ref platforms-gl-es-angle for further information.

*/

}