command: add platform property

This returns the value of the target OS that mpv was built on as
reported by the build system. It is quite conceivable that script
writers and API users would need to make OS-dependent choices in some
cases. Such people end up writing boilerplate/hacks to guess what OS
they are on. Assuming you trust the build system (if you don't, we're in
really deep trouble), then mpv actually knows exactly what OS it was
built on. Simply take this information at configuration time, make it a
define, and let mp_property_platform return the value.

Note that mpv has two build systems (waf and meson), so the names of the
detected OSes may not be exactly the same. Since meson is the newer
build system, the value of this property follows meson's naming
conventions*. In the waf build, there is a small function to map known
naming deviations to match meson (i.e. changing "win32" to "windows").
waf's documentation is a nightmare to follow, but it seems to simply
take the output of sys.platform in python and strip away any trailing
numbers if they exist (exception being win32 and os2)*.

*: https://mesonbuild.com/Reference-tables.html#operating-system-names
*: https://waf.io/apidocs/Utils.html#waflib.Utils.unversioned_sys_platform

1 files changed, 2 insertions, 0 deletions

diff --git a/wscript b/wscript
index 567fc67ff0..da90c97253 100644
--- a/wscript
+++ b/wscript
@@ -1054,6 +1054,8 @@ def configure(ctx):
     ctx.parse_dependencies(video_output_features)
     ctx.parse_dependencies(hwaccel_features)
 
+    ctx.define('PLATFORM', check_platform(ctx))
+
     if ctx.options.SWIFT_FLAGS:
         ctx.env.SWIFT_FLAGS.extend(split(ctx.options.SWIFT_FLAGS))