Revamp a couple of tf2 tutorials to flow better. (ros2#2781)

* Revamp a couple of tf2 tutorials to flow better.

That is, make sure we put in all the steps that need to be
done, and more logically organize the sections.  This should
make them easier to follow.

Signed-off-by: Chris Lalancette <clalancette@openrobotics.org>

source/Tutorials/Intermediate/Tf2/Adding-A-Frame-Py.rst

@@ -125,7 +125,6 @@ Now open the file called ``fixed_frame_tf2_broadcaster.py``.
 
       rclpy.shutdown()
 
-Don't forget to add the node to the ``setup.py``.
 The code is very similar to the tf2 broadcaster tutorial example and the only difference is that the transform here does not change over time.
 
 1.1 Examine the code
@@ -145,11 +144,23 @@ The ``carrot1`` frame is 2 meters offset in y axis in terms of the ``turtle1`` f
    t.transform.translation.y = 2.0
    t.transform.translation.z = 0.0
 
-1.2 Write the launch file
+1.2 Add an entry point
+~~~~~~~~~~~~~~~~~~~~~~
+
+To allow the ``ros2 run`` command to run your node, you must add the entry point
+to ``setup.py`` (located in the ``src/learning_tf2_py`` directory).
+
+Finally, add the following line between the ``'console_scripts':`` brackets:
+
+.. code-block:: python
+
+    'fixed_frame_tf2_broadcaster = learning_tf2_py.fixed_frame_tf2_broadcaster:main',
+
+1.3 Write the launch file
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Now let's create a launch file for this example.
-With your text editor, create a new file called ``turtle_tf2_fixed_frame_demo.launch.py``, and add the following lines:
+With your text editor, create a new file called ``launch/turtle_tf2_fixed_frame_demo.launch.py``, and add the following lines:
 
 .. code-block:: python
 
@@ -193,7 +204,8 @@ The last part of the code will add our fixed ``carrot1`` frame to the turtlesim
       name='fixed_broadcaster',
    ),
 
-1.3 Build and run
+
+1.4 Build and run
 ~~~~~~~~~~~~~~~~~
 
 Rebuild the package and start the turtle broadcaster demo:
@@ -206,7 +218,7 @@ You should notice that the new ``carrot1`` frame appeared in the transformation
 
 .. image:: images/turtlesim_frames_carrot.png
 
-1.4 Checking the results
+1.5 Checking the results
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 If you drive the first turtle around, you should notice that the behavior didn't change from the previous tutorial, even though we added a new frame.
@@ -334,10 +346,22 @@ Instead of a fixed definition of our x and y offsets, we are using the ``sin()``
    t.transform.translation.x = 10 * math.sin(x)
    t.transform.translation.y = 10 * math.cos(x)
 
-2.2 Write the launch file
+2.2 Add an entry point
+~~~~~~~~~~~~~~~~~~~~~~
+
+To allow the ``ros2 run`` command to run your node, you must add the entry point
+to ``setup.py`` (located in the ``src/learning_tf2_py`` directory).
+
+Finally, add the following line between the ``'console_scripts':`` brackets:
+
+.. code-block:: python
+
+    'dynamic_frame_tf2_broadcaster = learning_tf2_py.dynamic_frame_tf2_broadcaster:main',
+
+2.3 Write the launch file
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
-To test this code, create a new launch file ``turtle_tf2_dynamic_frame_demo.launch.py`` and paste the following code:
+To test this code, create a new launch file ``launch/turtle_tf2_dynamic_frame_demo.launch.py`` and paste the following code:
 
 .. code-block:: python
 
@@ -369,7 +393,7 @@ To test this code, create a new launch file ``turtle_tf2_dynamic_frame_demo.laun
          ),
       ])
 
-2.3 Build and run
+2.4 Build and run
 ~~~~~~~~~~~~~~~~~
 
 Rebuild the package, and start the ``turtle_tf2_dynamic_frame_demo.launch.py`` launch file, and now you’ll see that the second turtle is following the carrot's position that is constantly changing.

source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Listener-Cpp.rst

@@ -381,7 +381,7 @@ In the second terminal window type the following command:
 
   ros2 run turtlesim turtle_teleop_key
 
-3 Checking the results
+4 Checking the results
 ^^^^^^^^^^^^^^^^^^^^^^
 
 To see if things work, simply drive around the first turtle using the arrow keys (make sure your terminal window is active, not your simulator window), and you'll see the second turtle following the first one!

source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Listener-Py.rst

@@ -216,8 +216,20 @@ All this is wrapped in a try-except block to handle possible exceptions.
         from_frame_rel,
         now)
 
-2 Build and run
-^^^^^^^^^^^^^^^
+1.2 Add an entry point
+~~~~~~~~~~~~~~~~~~~~~~
+
+To allow the ``ros2 run`` command to run your node, you must add the entry point
+to ``setup.py`` (located in the ``src/learning_tf2_py`` directory).
+
+Finally, add the following line between the ``'console_scripts':`` brackets:
+
+.. code-block:: python
+
+    'turtle_tf2_listener = learning_tf2_py.turtle_tf2_listener:main',
+
+2 Update the launch file
+^^^^^^^^^^^^^^^^^^^^^^^^
 
 With your text editor, open the launch file called ``turtle_tf2_demo.launch.py``, and add the following lines after your first ``turtle1`` broadcaster node.
 Additionally, include the imports of ``DeclareLaunchArgument`` and ``LaunchConfiguration`` in the beginning of the file:
@@ -256,6 +268,34 @@ Additionally, include the imports of ``DeclareLaunchArgument`` and ``LaunchConfi
         ])
 
 This will declare a ``target_frame`` launch argument, start a broadcaster for second turtle that we will spawn and listener that will subscribe to those transformations.
+
+
+3 Build and run
+^^^^^^^^^^^^^^^
+
+Run ``rosdep`` in the root of your workspace to check for missing dependencies.
+
+.. tabs::
+
+   .. group-tab:: Linux
+
+      .. code-block:: console
+
+        rosdep install -i --from-path src --rosdistro {DISTRO} -y
+
+   .. group-tab:: macOS
+
+        rosdep only runs on Linux, so you will need to install ``geometry_msgs``, ``tf_transformations`` and ``turtlesim`` dependencies yourself
+
+   .. group-tab:: Windows
+
+        rosdep only runs on Linux, so you will need to install ``geometry_msgs``, ``tf_transformations`` and ``turtlesim`` dependencies yourself
+
+Build your updated package, and source the setup files.
+
+4 Checking the results
+^^^^^^^^^^^^^^^^^^^^^^
+
 Now you're ready to start your full turtle demo:
 
 .. code-block:: console
@@ -269,9 +309,6 @@ In the second terminal window type the following command:
 
     ros2 run turtlesim turtle_teleop_key
 
-3 Checking the results
-^^^^^^^^^^^^^^^^^^^^^^
-
 To see if things work, simply drive around the first turtle using the arrow keys (make sure your terminal window is active, not your simulator window), and you'll see the second turtle following the first one!
 
 Summary