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[WIP]: WaitForTransform Python (#194) #215

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[WIP]: WaitForTransform Python (#194) #215

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25 changes: 16 additions & 9 deletions tf2_ros/src/tf2_ros/buffer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -218,6 +218,18 @@ def can_transform_full(self, target_frame, target_time, source_frame, source_tim
return core_result
return core_result[0]

def _wait_for_transform_async(self, target_Frame, source_frame, time, callback):
fut = rclpy.task.Future()
if self.can_transform_core(target_frame, source_frame, time)[0]:
# Short cut, the transform is available
fut.set_result(True)
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@sloretz sloretz Jan 13, 2020

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On #194 you wrote:

the result on future doesn't contain any info about the transform. It should probably have that.

Can you please clarify what information you're hoping to propagate up?

I was trying to say it would be nice if fut.result() returned the transform that was being waited for instead of True.

return fut

self._new_data_callbacks.append(callback)
fut.add_done_callback(lambda _: self._remove_callback(callback))

return fut

def wait_for_transform_async(self, target_frame, source_frame, time):
"""
Wait for a transform from the source frame to the target frame to become possible.
Expand All @@ -228,23 +240,15 @@ def wait_for_transform_async(self, target_frame, source_frame, time):
:return: A future that becomes true when the transform is available
:rtype: rclpy.task.Future
"""
fut = rclpy.task.Future()
if self.can_transform_core(target_frame, source_frame, time)[0]:
# Short cut, the transform is available
fut.set_result(True)
return fut

def _on_new_data():
try:
if self.can_transform_core(target_frame, source_frame, time)[0]:
fut.set_result(True)
except BaseException as e:
fut.set_exception(e)

self._new_data_callbacks.append(_on_new_data)
fut.add_done_callback(lambda _: self._remove_callback(_on_new_data))
return _wait_for_transform_async(self, target_frame, source_frame, time, _on_new_data)

return fut

def wait_for_transform_full_async(self, target_frame, target_time, source_frame, source_time, fixed_frame):
"""
Expand Down Expand Up @@ -275,3 +279,6 @@ def _on_new_data():
fut.add_done_callback(lambda _: self._remove_callback(_on_new_data))

return fut

def wait_for_transform(target_frame, source_frame, time, callback):
return _wait_for_transform_async(target_frame, source_frame, time, callback)
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@sloretz sloretz Jan 13, 2020

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Instead of adding wait_for_transform(..., callback), with ros2/rclpy#460 merged I think the utility #194 is asking for can be had by making the result on the future returned by wait_for_transform_async() contain the transform data. The interface someone would use is fut = wait_for_transform_async(...); fut.add_done_callback(my_tf_callback).