Documentation work

.github/CONTRIBUTING.md

@@ -309,6 +309,10 @@ did not write the code yourself, you must explain where it came from and under
 what license.  Even code using the same license as GLFW may not be copied
 without attribution.
 
+__Note:__ If you haven't already implemented the feature, check first if there
+already is an open issue for it and if it's already being developed in an
+[experimental branch](https://github.com/glfw/glfw/branches/all).
+
 __There is no preferred patch size__.  A one character change is just as welcome
 as one adding a thousand line one, if that is the appropriate size for the
 feature.

README.md

@@ -10,6 +10,10 @@ GLFW is an Open Source, multi-platform library for OpenGL, OpenGL ES and Vulkan
 application development.  It provides a simple, platform-independent API for
 creating windows, contexts and surfaces, reading input, handling events, etc.
 
+GLFW natively supports Windows, macOS and Linux and other Unix-like systems.
+Experimental implementations for the Wayland protocol and the Mir display server
+are available but not yet officially supported.                             
+
 GLFW is licensed under the [zlib/libpng
 license](http://www.glfw.org/license.html).
 
@@ -23,6 +27,13 @@ The [version history](http://www.glfw.org/changelog.html) lists all user-visible
 changes for every release.
 
 This is a development branch for version 3.3, which is _not yet described_.
+Pre-release documentation is available [here](http://www.glfw.org/docs/3.3/).
+
+The `master` branch is the stable integration branch and _should_ always compile
+and run on all supported platforms, although details of newly added features may
+change until they have been included in a release.  New features and many bug
+fixes live in [other branches](https://github.com/glfw/glfw/branches/all) until
+they are stable enough to merge.
 
 If you are new to GLFW, you may find the
 [tutorial](http://www.glfw.org/docs/latest/quick.html) for GLFW
@@ -46,22 +57,29 @@ There are also [pre-compiled Windows
 binaries](http://www.glfw.org/download.html) available for all compilers
 supported on that platform.
 
-See the [compilation guide](http://www.glfw.org/docs/latest/compile.html) in the
-documentation for more information.
+See the [compilation guide](http://www.glfw.org/docs/latest/compile.html) for
+more information about how to compile GLFW.
 
 
 ## Using GLFW
 
-See the [building application guide](http://www.glfw.org/docs/latest/build.html)
-guide in the documentation for more information.
+See the [documentation](http://www.glfw.org/docs/latest/) for tutorials, guides
+and the API reference.
+
+
+## Contributing to GLFW
+
+See the [contribution
+guide](https://github.com/glfw/glfw/blob/master/.github/CONTRIBUTING.md) for
+more information.
 
 
 ## System requirements
 
-GLFW supports Windows XP and later, OS X 10.7 Lion and later, and Linux and
-other Unix-like systems with the X Window System.  Experimental implementations
-for the Wayland protocol and the Mir display server are available but not yet
-officially supported.
+GLFW supports Windows XP and later and macOS 10.7 and later.  Linux and other
+Unix-like systems running the X Window System are supported even without
+a desktop environment or modern extensions, although some features require
+a running window or clipboard manager.  The OSMesa backend requires Mesa 6.3.
 
 See the [compatibility guide](http://www.glfw.org/docs/latest/compat.html)
 in the documentation for more information.
@@ -87,7 +105,8 @@ located in the `deps/` directory.
  - [Vulkan headers](https://www.khronos.org/registry/vulkan/) for Vulkan tests
 
 The Vulkan example additionally requires the Vulkan SDK to be installed, or it
-will not be included in the build.
+will not be included in the build.  On macOS you need to set the path to the
+MoltenVK SDK manually as it has no standard location.
 
 The documentation is generated with [Doxygen](http://doxygen.org/).  If CMake
 does not find Doxygen, the documentation will not be generated when you build.