Add static cast for buffer data + force C++-17

[luca-della-vedova]

Bug fix

Fixed bug

Fixes builds on rolling.

Fix applied

Rolling builds for rmf_visualization_floorplans have been failing with this kind of error (from buildfarm):

/tmp/binarydeb/ros-rolling-rmf-visualization-floorplans-2.5.1/src/FloorplanVisualizer.cpp:77:39: error: no matching function for call to ‘cv::Mat::Mat(const rmf_building_map_msgs::msg::AffineImage_<std::allocator<void> >::_data_type&)’
   77 |           cv::Mat(level.images[0].data), cv::IMREAD_GRAYSCALE);
      |                                       ^
In file included from /usr/include/opencv4/opencv2/core.hpp:58,
                 from /usr/include/opencv4/opencv2/core/core.hpp:48,
                 from /tmp/binarydeb/ros-rolling-rmf-visualization-floorplans-2.5.1/src/FloorplanVisualizer.cpp:21:
/usr/include/opencv4/opencv2/core/mat.hpp:1057:37: note: candidate: ‘template<class _Tp> cv::Mat::Mat(const cv::MatCommaInitializer_<_Tp>&)’
 1057 |     template<typename _Tp> explicit Mat(const MatCommaInitializer_<_Tp>& commaInitializer);
      |                                     ^~~
/usr/include/opencv4/opencv2/core/mat.hpp:1057:37: note:   template argument deduction/substitution failed:
/tmp/binarydeb/ros-rolling-rmf-visualization-floorplans-2.5.1/src/FloorplanVisualizer.cpp:77:39: note:   ‘const rmf_building_map_msgs::msg::AffineImage_<std::allocator<void> >::_data_type’ {aka ‘const rosidl::Buffer<unsigned char, std::allocator<unsigned char> >’} is not derived from ‘const cv::MatCommaInitializer_<_Tp>’
   77 |           cv::Mat(level.images[0].data), cv::IMREAD_GRAYSCALE);

The issue seems to be due to the new Buffer introduced in rosidl, meant to be an abstraction for a CPU or GPU buffer.
It seems it can be implicitly converted do its inner std::vector (ref), so I just added a static_cast to the inner vector type. This should:

• Convert the buffer.
• Do nothing on older ROS versions where the data field is a std::vector in the first place.

Hence this should fix rolling builds without breaking compatibility with older ROS distros.

Furthermore, rmf_visualization_schedule builds are broken for a reason similar to rmf_websocket, with the difference that here it seems a transitive target is forcing the CXX version, so we need to override it.

Test it!

Build it under rolling (you will need to build rolling from source since it's not released yet), then build it under Jazzy.

GenAI Use

We follow OSRA's policy on GenAI tools

• I used a GenAI tool in this PR.
• I did not use GenAI

[luca-della-vedova]

We should probably revert the hacky C++-17 change but it is pending a fix on rmf_websocket itself to have it C++-20 compatible. Marking as draft for now.