This is a bugfix release.

This is a brief summary of the new features in Coin v4.0.1:

Version control system has been changed from Mercurial to Git.
Home of Coin3d organization has been changed from https://bitbucket.org/Coin3D to https://github.com/coin3d due to Bitbucket ending Mercurial support.
Added CI for macOS, Windows, and Ubuntu per GitHub actions to repository
Added checksum generation to AppVeyor CI
Added macOS images to AppVeyor CI
The expat sources under coin/src/xml/expat were updated to version 2.2.10.
Introduced new COIN_DEBUG_CHECK_THREAD option.
Introduced COIN_GLX_PIXMAP_DIRECT_RENDERING environment variable to force direct rendering of offscreen contexts.

Bug fixes:

Optimized mutex debugging.
Fix integer division issue.
Fix material and normal handling for indexed line set.
Fix resource lookup when HAVE_MULTIPLE_VERSION is enabled in CMake build script.
Fixed an transparency issue for indexed lineset.
Move constant data to read only data segment to reduce size of shared object library (see https://randomascii.wordpress.com/2017/01/08/add-a-const-here-delete-a-const-there)
Fixed numerous issues detected by static code analysis.
Fix linking with system installation of expat.
Fix broken ABI version on .so link.
Do not run programs for determining hash quoting to support cross compiling.
Fix testing for maximum texture size.
Removed obsolete ATI driver issue check. Do not check for ATI driver issues fixed long time ago (see issue #412). We added environment variable COIN_GLGLUE_DISABLE_VBO_IN_DISPLAYLIST for compatibility with the old behaviour.
Fix underlinking against X11 in CMake build scripts.
Set GLSL shader version to 120 to avoid rendering issues with fog.
Enable non power of two textures for ATi and Intel by default. For those who are in need of the old behavior, an environment variable COIN_GLGLUE_DISABLE_NON_POWER_OF_TWO_TEXTURES has been added.
Do not disable VBO rendering for Intel graphics drivers anymore. Recent Intel graphics hardware is known to properly support VBO rendering. So we remove the code for disabling it by default.
Fix GLX glue trying to use NULL display, i.e. when a unix platform has a non-GLX context: usually Wayland, but also might be offscreen or maybe EGL-X11.
Fix operator arguments on some base types to use const references rather than copies.
Fixed incorrect rendering of SoFaceSet. Conditions when to render as VertexArrayObject were not properly checked.
Fixed incorrect line ending handling for Windows CR/LF.
Fixed incorrect closest point calculation for bounding boxes.
Applied some distribution patches from Fedora, Rosa, and Gentoo.
Added some class documentation and fixed numerous documentation issues.
cpack.d was made optional and disabled by default (add -DCOIN_USE_CPACK=ON to the cmake commandline to enable it).
Reference line for text rendered with the built-in default font was changed (before: descender line, now: base line). Thus text rendered with default font will appear a few pixels lower than before, but now consistent with text using non-default fonts. (see https://github.com/coin3d/coin/pull/368)
Fixed crash when call to cc_flww32_get_bitmap() failed.