rviz_ogre_vendor: fails to build due to compatibility with CMake < 3.5 has been removed from CMake.

[zumbi]

When building rviz_ogre_vendor with newer CMake:

--- stderr: rviz_ogre_vendor                              
CMake Error at CMakeLists.txt:17 (cmake_minimum_required):
  Compatibility with CMake < 3.5 has been removed from CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.

  Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.


gmake[2]: *** [CMakeFiles/ogre_vendor.dir/build.make:93: ogre_vendor-prefix/src/ogre_vendor-stamp/ogre_vendor-configure] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:153: CMakeFiles/ogre_vendor.dir/all] Error 2
gmake: *** [Makefile:146: all] Error 2
---
Failed   <<< rviz_ogre_vendor [41.2s, exited with code 2]

This is caused by vendored ogre_vendor version:

rviz/rviz_ogre_vendor/CMakeLists.txt

Line 86 in c2cc241

VCS_VERSION v1.12.10

this brings the minimum required version for CMake of 3.3.0 which causes issues with newer CMake.
https://github.com/OGRECave/ogre/blob/1316cf2cb8a1f9284aecc9225e5c775a168a491e/CMakeLists.txt#L17

I am not sure how best to fix this issue, either vendor latest ogre version and update patchset or use system provided library.

Thanks very much for your support.

[mjcarroll]

I ran into this on Windows as well via pixi. As a temporary stopgap, you can add the POLICY_VERSION_MINIMUM to the vendor package arguments here: https://github.com/ros2/rviz/blob/rolling/rviz_ogre_vendor/CMakeLists.txt#L84-L113

It will continue to build, but doesn't seem like the optimal long-term fix here.

[wjwwood]

I used this diff to workaround this on a pixi based build on macos:

diff --git a/rviz_ogre_vendor/CMakeLists.txt b/rviz_ogre_vendor/CMakeLists.txt
index 353a0e6c..54782e03 100644
--- a/rviz_ogre_vendor/CMakeLists.txt
+++ b/rviz_ogre_vendor/CMakeLists.txt
@@ -70,6 +70,7 @@ ament_vendor(ogre_vendor
     -DOGRE_MANGLE_NAME_OF_LIBRARIES_USED_BY_RVIZ:BOOL=${RVIZ_OGRE_VENDOR_MANGLE_NAME_OF_LIBRARIES_USED_BY_RVIZ}
     "-DCMAKE_CXX_FLAGS=${OGRE_CXX_FLAGS}"
     ${OGRE_CMAKE_ARGS}
+    -DCMAKE_POLICY_VERSION_MINIMUM=3.5
   PATCHES patches
 )

[mjcarroll]

I think that we could probably just go ahead and put this in, it doesn't seem to hurt anything.

The longer term goal would be to advance the OGRE version, but we would need someone to take that on.