Apriltags-cpp should be checked out at clone, not at build time about apriltags

[psigen]

One option might be to use the following option to ExternalProject:

If UPDATE_DISCONNECTED is set, the update step is not executed automatically when building the
main target. The update step can still be added as a step target and called manually. This is
useful if you want to allow to build the project when you are disconnected from the network (you
might still need the network for the download step). This is disabled by default. The directory
property EP_UPDATE_DISCONNECTED can be used to change the default value for all the external
projects in the current directory and its subdirectories.

https://cmake.org/cmake/help/v3.2/module/ExternalProject.html

[davelkan-zz]

This is only a valid option with Cmake 3.2 or later. People using indigo for example cannot use this option. I would argue therefore that this is still an issue. There is no real reason Apriltags users should need internet to build.

[andre-nguyen]

This is indeed a problem for me since sometimes I do tests in the field without internet access. Any idea how to fix this easily?

[andre-nguyen]

I ended up doing a quick and dirty hack to catkinize https://github.com/swatbotics/apriltags-cpp and put it as a dependency of this repo. I doubt this is the direction you guys seem to be aiming for though.

[psigen]

Actually, in discussions with @mkoval, we concluded that catkin-izing the apriltags upstream library is probably The Right Thing for this case.

@andre-nguyen can you make a PR for the catkinization over at https://github.com/swatbotics/apriltags-cpp ?

@ClintLiddick, if you and @mkoval can help check it over and give it the OK, I'll merge it up there. Then we can change this package to simply use CMake to FindApriltags(), and change the directions to have people check out both packages together.

This may be useful as a step towards #19 anyway.

[davelkan-zz]

This sounds like a great plan to me.

[mkoval]

I agree with @psigen that The Right Thing is to build the upstream library as a separate package. All we need to do is modify the upstream repository to follow REP-136 by:

1. adding a package.xml file with <build_type>cmake</build_type>
2. adding an install(FILES) rule for the package.xml file
3. using configure_package_config_file() to generate a ApriltagsConfig.cmake file

You can see an example of this in Aikido's package.xml and CMakeLists.txt files.

Once this is done, this package can depend on Apriltags using find_package(Apriltags). The two packages may be built in the same workspace using catkin_make_isolated or catkin build.

[andre-nguyen]

I see.

This isn't quite how I did it here swatbotics/apriltags-cpp#8 but your method seems cleaner. I'll leave it up for anyone who just want's to have the quick fix.

[davelkan-zz]

Any updates on this?

[psigen]

Not at the moment, I think everyone's just been pretty busy recently.

[Asukamax]

Excuse me .I'm a newbie.
I don't know how to use this package ,even I could build it ,run the launch file successful...
When I run the apriltags.launch ,it seem like doing nothing?
Is that I should run some node to make my camera active and publish the image imformation to topic?
If is that , which package I could use?

Thanks a lot

[psigen]

@Asukamax: It's normally useful to create a new issue for different topics, so I've created one here for you #23. Feel free to post followup questions there.

[psigen]

Fixed in #25