GLFW: Standards conformance

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Standards conformance

This guide 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 intending to deploy their applications on a wide range of machines.

The information in this guide is not a part of GLFW API, but merely preconditions for some parts of the library to function on a given machine. Any part of this information may change in future versions of GLFW and that will not be considered a breaking API change.

# X11 extensions, protocols and IPC standards

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 (ICCCM) and Extended Window Manager Hints (EWMH) standards.

GLFW uses the `_MOTIF_WM_HINTS` window property to support borderless windows. If the running window manager does not support this property, the `GLFW_DECORATED` hint will have no effect.

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

GLFW uses the EWMH `_NET_WM_BYPASS_COMPOSITOR` window property to tell a compositing window manager to un-redirect full screen GLFW windows. If the running window manager uses compositing but does not support this property then additional copying may be performed for each buffer swap of full screen windows.

GLFW uses the clipboard manager protocol 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.

GLFW uses the X drag-and-drop protocol to provide file drop events. If the application originating the drag does not support this protocol, drag and drop will not work.

GLFW uses the XRandR 1.3 extension to provide multi-monitor support. If the running X server does not support this version of this extension, multi-monitor support will not function and only a single, desktop-spanning monitor will be reported.

GLFW uses the XRandR 1.3 and Xf86vidmode extensions to provide gamma ramp support. If the running X server does not support either or both of these extensions, gamma ramp support will not function.

GLFW uses the Xkb extension and detectable auto-repeat to provide keyboard input. If the running X server does not support this extension, a non-Xkb fallback path is used.

# 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 GLX 1.3 `GLXFBConfig` functions to enumerate and select framebuffer pixel formats. If GLX 1.3 is not supported, glfwInit will fail.

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 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 `GLFW_TRUE` will cause 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 `GLFW_OPENGL_ANY_PROFILE`, or setting `GLFW_CLIENT_API` to anything but `GLFW_OPENGL_API` or `GLFW_NO_API` will cause glfwCreateWindow to fail.

GLFW uses the `GLX_ARB_context_flush_control` extension to provide control over whether a context is flushed when it is released (made non-current). Where this extension is unavailable, the `GLFW_CONTEXT_RELEASE_BEHAVIOR` hint will have no effect and the context will always be flushed when released.

GLFW uses the `GLX_ARB_framebuffer_sRGB` and `GLX_EXT_framebuffer_sRGB` extensions to provide support for sRGB framebuffers. Where both of these extensions are unavailable, the `GLFW_SRGB_CAPABLE` hint will have no effect.

# 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 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 `GLFW_TRUE` will cause 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 `GLFW_OPENGL_ANY_PROFILE` will cause glfwCreateWindow to fail.

GLFW uses the `WGL_ARB_context_flush_control` extension to provide control over whether a context is flushed when it is released (made non-current). Where this extension is unavailable, the `GLFW_CONTEXT_RELEASE_BEHAVIOR` hint will have no effect and the context will always be flushed when released.

GLFW uses the `WGL_ARB_framebuffer_sRGB` and `WGL_EXT_framebuffer_sRGB` extensions to provide support for sRGB framebuffers. Where both of these extension are unavailable, the `GLFW_SRGB_CAPABLE` hint will have no effect.

# 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 glfwCreateWindow to fail if given version 3.0 or 3.1, the `GLFW_OPENGL_FORWARD_COMPAT` hint must be set to `GLFW_TRUE` and the `GLFW_OPENGL_PROFILE` hint must be set to `GLFW_OPENGL_CORE_PROFILE` when creating OpenGL 3.2 and later contexts and the `GLFW_OPENGL_DEBUG_CONTEXT` hint is ignored.

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, setting the `GLFW_OPENGL_PROFILE` or `GLFW_OPENGL_FORWARD_COMPAT` hints to a non-default value will cause glfwCreateWindow to fail and the `GLFW_OPENGL_DEBUG_CONTEXT` hint is ignored.

# Vulkan loader and API

GLFW uses the standard system-wside Vulkan loader to access the Vulkan API. This should be installed by graphics drivers and Vulkan SDKs. If this is not available, glfwVulkanSupported will return `GLFW_FALSE` and all other Vulkan-related functions will fail with an GLFW_API_UNAVAILABLE error.

# Vulkan WSI extensions

The Vulkan WSI extensions are used to create Vulkan surfaces for GLFW windows on all supported platforms.

GLFW uses the `VK_KHR_surface` and `VK_KHR_win32_surface` extensions to create surfaces on Microsoft Windows. If any of these extensions are not available, glfwGetRequiredInstanceExtensions will return an empty list and window surface creation will fail.

GLFW uses the `VK_KHR_surface` and either the `VK_KHR_xlib_surface` or `VK_KHR_xcb_surface` extensions to create surfaces on X11. If `VK_KHR_surface` or both `VK_KHR_xlib_surface` and `VK_KHR_xcb_surface` are not available, glfwGetRequiredInstanceExtensions will return an empty list and window surface creation will fail.

GLFW uses the `VK_KHR_surface` and `VK_KHR_wayland_surface` extensions to create surfaces on Wayland. If any of these extensions are not available, glfwGetRequiredInstanceExtensions will return an empty list and window surface creation will fail.

GLFW uses the `VK_KHR_surface` and `VK_KHR_mir_surface` extensions to create surfaces on Mir. If any of these extensions are not available, glfwGetRequiredInstanceExtensions will return an empty list and window surface creation will fail.

GLFW does not support any extensions for window surface creation on OS X, meaningglfwGetRequiredInstanceExtensions will return an empty list and window surface creation will fail.