geometry2
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ros2
Python call callback with transform data when it becomes available
Feature
It would be convenient if there was an API that returned transform information in a callback.
Feature description
It looks like C++ has an overload of waits_for_transform that calls the callback with a future containing the transform.
https://github.com/ros2/geometry2/blob/71f823e90b699c9535ce682db777f7bc88cdfbcd/tf2_ros/include/tf2_ros/buffer.h#L214-L216
Implementation considerations
It should be possible using the callbacks on the future returned by wait_for_transform_async, however the returned future is not associated with an executor so done callbacks are never called (ros2/rclpy#460).
https://github.com/ros2/geometry2/blob/71f823e90b699c9535ce682db777f7bc88cdfbcd/tf2_ros/src/tf2_ros/buffer.py#L217-L226
However, even if the done callbacks were called the result on future doesn't contain any info about the transform. It should probably have that.
@sloretz would you mind if I looked into doing this?
@allenh1 please do, and thank you!
It should be possible using the callbacks on the future returned by wait_for_transform_async, however the returned future is not associated with an executor so done callbacks are never called (ros2/rclpy#460).
@sloretz since the issue you mentioned is closed now, I'm assuming this can be done as you were saying by using wait_for_transform_async, right? I'll send a PR in with that assumption and we can talk further if that wasn't a good one.
I've removed myself from this because I don't have the time to do this before the galactic release. Anyone who feels led to should feel free to pick up this issue. Otherwise, I might have time in a while to revisit this.