FindOpenGL: Add policy CMP0072 to prefer GLVND for legacy GL

Fixes: #17449

1 files changed, 26 insertions, 0 deletions

diff --git a/Help/policy/CMP0072.rst b/Help/policy/CMP0072.rst
new file mode 100644
index 0000000..3abbad7
--- /dev/null
+++ b/Help/policy/CMP0072.rst
@@ -0,0 +1,26 @@
+CMP0072
+-------
+
+:module:`FindOpenGL` prefers GLVND by default when available.
+
+The :module:`FindOpenGL` module provides an ``OpenGL::GL`` target and an
+``OPENGL_LIBRARIES`` variable for projects to use for legacy GL interfaces.
+When both a legacy GL library (e.g. ``libGL.so``) and GLVND libraries
+for OpenGL and GLX (e.g. ``libOpenGL.so`` and ``libGLX.so``) are available,
+the module must choose between them.  It documents an ``OpenGL_GL_PREFERENCE``
+variable that can be used to specify an explicit preference.  When no such
+preference is set, the module must choose a default preference.
+
+CMake 3.11 and above prefer to choose GLVND libraries.  This policy provides
+compatibility with projects that expect the legacy GL library to be used.
+
+The ``OLD`` behavior for this policy is to set ``OpenGL_GL_PREFERENCE`` to
+``LEGACY``.  The ``NEW`` behavior for this policy is to set
+``OpenGL_GL_PREFERENCE`` to ``GLVND``.
+
+This policy was introduced in CMake version 3.11.  CMake version
+|release| warns when the policy is not set and uses ``OLD`` behavior.
+Use the :command:`cmake_policy` command to set it to ``OLD`` or ``NEW``
+explicitly.
+
+.. include:: DEPRECATED.txt