Mesa removed that library in 027ccd963b1f8f288bef4224aedcddc1557e4f8a,
so this API can be removed from GLFW too.
Mesa has provided an alternative path for years, through the
EGL_MESA_platform_surfaceless EGL extension, and it also supports
selecting the software rasterizer through the EGL_EXT_platform_device
EGL extension, neither of which are supported by GLFW yet.
I kept the external API the same, notably the GLFW_OSMESA_CONTEXT_API
define is still present, but will error at runtime.
There will not currently be more than one set of threading or timer APIs
selected regardless of how many window systems are enabled, so there is
no need for this extra complexity.
This adds compile-time support for multiple platforms and runtime
detection of them. Window system related platform functions are now
called from shared code via the function pointer struct _GLFWplatform.
The timer, thread and module loading platform functions are still called
directly by name and the implementation chosen at link-time. These
functions are the same for any backend on a given OS, including the Null
backend.
The platforms are now enabled via CMake dependent options following the
GLFW_BUILD_<platform> pattern instead of a mix of automagic and ad-hoc
option names. There is no longer any option for the Null backend as it
is now always enabled.
Much of the struct stitching work in platform.h was based on an earlier
experimental branch for runtime platform selection by @ronchaine.
Every platform function related to windows, contexts, monitors, input,
event processing and Vulkan have been renamed so that multiple sets of
them can exist without colliding. Calls to these are now routed through
the _glfw.platform struct member. These changes makes up most of this
commit.
For Wayland and X11 the client library loading and display creation is
used to detect a running compositor/server. The XDG_SESSION_TYPE
environment variable is ignored for now, as X11 is still by far the more
complete implementation.
Closes#1655Closes#1958
