glfw/docs/compat.dox

/*!

@page compat Standards conformance

@tableofcontents

This chapter describes the various API extensions used by this version of GLFW.
It lists what are essentially implementation details, but which are nonetheless
vital knowledge for developers wishing to deploy their applications on machines
with varied specifications.

Note that the information in this appendix is not a part of the API
specification but merely list some of the preconditions for certain parts of the
API to function on a given machine.  As such, any part of it may change in
future versions without this being considered a breaking API change.

@section compat_wm ICCCM and EWMH conformance

As GLFW uses Xlib, directly, without any intervening toolkit
library, it has sole responsibility for interacting well with the many and
varied window managers in use on Unix-like systems.  In order for applications
and window managers to work well together, a number of standards and
conventions have been developed that regulate behavior outside the scope of the
X11 API; most importantly the
[Inter-Client Communication Conventions Manual](http://www.tronche.com/gui/x/icccm/)
(ICCCM) and
[Extended Window Manager Hints](http://standards.freedesktop.org/wm-spec/wm-spec-latest.html)
(EWMH) standards.

GLFW uses the ICCCM `WM_DELETE_WINDOW` protocol to intercept the user
attempting to close the GLFW window.  If the running window manager does not
support this protocol, the close callback will never be called.

GLFW uses the EWMH `_NET_WM_PING` protocol, allowing the window manager notify
the user when the application has stopped responding, i.e. when it has ceased to
process events.  If the running window manager does not support this protocol,
the user will not be notified if the application locks up.

GLFW uses the EWMH `_NET_WM_STATE` protocol to tell the window manager to make
the GLFW window full screen.  If the running window manager does not support this
protocol, full screen windows may not work properly.  GLFW has a fallback code
path in case this protocol is unavailable, but every window manager behaves
slightly differently in this regard.

GLFW uses the
[clipboard manager protocol](http://www.freedesktop.org/wiki/ClipboardManager/)
to push a clipboard string (i.e. selection) owned by a GLFW window about to be
destroyed to the clipboard manager.  If there is no running clipboard manager,
the clipboard string will be unavailable once the window has been destroyed.

@section compat_glx GLX extensions

The GLX API is the default API used to create OpenGL contexts on Unix-like
systems using the X Window System.

GLFW uses the `GLXFBConfig` API to enumerate and select framebuffer pixel
formats.  This requires either GLX 1.3 or greater, or the `GLX_SGIX_fbconfig`
extension.  Where both are available, the SGIX extension is preferred.  If
neither is available, GLFW will be unable to create windows.

GLFW uses the `GLX_MESA_swap_control,` `GLX_EXT_swap_control` and
`GLX_SGI_swap_control` extensions to provide vertical retrace synchronization
(or "vsync"), in that order of preference.  Where none of these extension are
available, calling @ref glfwSwapInterval will have no effect.

GLFW uses the `GLX_ARB_multisample` extension to create contexts with
multisampling anti-aliasing.  Where this extension is unavailable, the
`GLFW_SAMPLES` hint will have no effect.

GLFW uses the `GLX_ARB_create_context` extension when available, even when
creating OpenGL contexts of version 2.1 and below.  Where this extension is
unavailable, the `GLFW_CONTEXT_VERSION_MAJOR` and `GLFW_CONTEXT_VERSION_MINOR`
hints will only be partially supported, the `GLFW_OPENGL_DEBUG_CONTEXT` hint
will have no effect, and setting the `GLFW_OPENGL_PROFILE` or
`GLFW_OPENGL_FORWARD_COMPAT` hints to a non-zero value will cause @ref
glfwCreateWindow to fail.

GLFW uses the `GLX_ARB_create_context_profile` extension to provide support for
context profiles.  Where this extension is unavailable, setting the
`GLFW_OPENGL_PROFILE` hint to anything but zero, or setting `GLFW_CLIENT_API` to
anything but `GLFW_OPENGL_API` will cause @ref glfwCreateWindow to fail.

@section compat_wgl WGL extensions

The WGL API is used to create OpenGL contexts on Microsoft Windows and other
implementations of the Win32 API, such as Wine.

GLFW uses either the `WGL_EXT_extension_string` or the
`WGL_ARB_extension_string` extension to check for the presence of all other WGL
extensions listed below.  If both are available, the EXT one is preferred.  If
neither is available, no other extensions are used and many GLFW features
related to context creation will have no effect or cause errors when used.

GLFW uses the `WGL_EXT_swap_control` extension to provide vertical retrace
synchronization (or 'vsync').  Where this extension is unavailable, calling @ref
glfwSwapInterval will have no effect.

GLFW uses the `WGL_ARB_pixel_format` and `WGL_ARB_multisample` extensions to
create contexts with multisampling anti-aliasing.  Where these extensions are
unavailable, the `GLFW_SAMPLES` hint will have no effect.

GLFW uses the `WGL_ARB_create_context` extension when available, even when
creating OpenGL contexts of version 2.1 and below.  Where this extension is
unavailable, the `GLFW_CONTEXT_VERSION_MAJOR` and `GLFW_CONTEXT_VERSION_MINOR`
hints will only be partially supported, the `GLFW_OPENGL_DEBUG_CONTEXT` hint
will have no effect, and setting the `GLFW_OPENGL_PROFILE` or
`GLFW_OPENGL_FORWARD_COMPAT` hints to a non-zero value will cause @ref
glfwCreateWindow to fail.

GLFW uses the `WGL_ARB_create_context_profile` extension to provide support for
context profiles.  Where this extension is unavailable, setting the
`GLFW_OPENGL_PROFILE` hint to anything but zero will cause @ref glfwCreateWindow
to fail.

@section compat_osx OpenGL 3.2 and later on OS X

Support for OpenGL 3.2 and above was introduced with OS X 10.7 and even then
only forward-compatible, core profile contexts are supported.  Support for
OpenGL 4.1 was introduced with OS X 10.9, also limited to forward-compatible,
core profile contexts.  There is also still no mechanism for requesting debug
contexts.  Versions of Mac OS X earlier than 10.7 support at most OpenGL
version 2.1.

Because of this, on OS X 10.7 and later, the `GLFW_CONTEXT_VERSION_MAJOR` and
`GLFW_CONTEXT_VERSION_MINOR` hints will cause @ref glfwCreateWindow to fail if
given version 3.0 or 3.1, the `GLFW_OPENGL_FORWARD_COMPAT` is required for
creating contexts for OpenGL 3.2 and later, the `GLFW_OPENGL_DEBUG_CONTEXT` hint
is ignored and setting the `GLFW_OPENGL_PROFILE` hint to anything except
`GLFW_OPENGL_CORE_PROFILE` will cause @ref glfwCreateWindow to fail.

Also, on Mac OS X 10.6 and below, the `GLFW_CONTEXT_VERSION_MAJOR` and
`GLFW_CONTEXT_VERSION_MINOR` hints will fail if given a version above 2.1, the
`GLFW_OPENGL_DEBUG_CONTEXT` hint will have no effect, and setting the
`GLFW_OPENGL_PROFILE` or `GLFW_OPENGL_FORWARD_COMPAT` hints to a non-zero value
will cause @ref glfwCreateWindow to fail.

*/