# ForDevelopers

## Introduction

The success of the VTK Examples depends on the contributions from the VTK user community. If you wish to contribute to this valuable resource, please follow these guidelines. If you are a VTK Example User, go here or an Example Administrator go here.

C++, C#, Python and Java examples are welcome! Examples should illustrate a single concept.

## Follow the Coding Guidelines

When you write an example, please follow the coding guidelines. Create the example on your local repository, compile and run it before you generate a pull request.

Some additional steps need to be done for Python C# and Java, see the sections below.

## Setup for Development

### Fork the repository

1. Sign into github.

   If you do not have an account, you can register on the signin page.

2. Fork the VTKExamples repository

   A fork is a copy of a project. Forking a repository allows you to make changes without affecting the original project.

3. Enable a static web site for the examples.

   Under Settings, GitHub Pages, set the Source to master branch and click Save.

4. Clone the repository on your local machine

   `git clone https://YOURNAME@github.com/YOURNAME/VTKExamples.git`

   Or, if you are using SSH:

   `git clone git@github.com:YOURNAME/VTKExamples.git`

   where YOURNAME is your github username.

5. Add the VTKExamples repository as a remote called upstream

   `git remote add upstream https://github.com/lorensen/VTKExamples`

6. Before adding your examples, sync your repository with the VTKExamples repository. Remember that in order to run the following commands you need to be in the VTKExamples directory.

   `git fetch upstream`

   `git checkout master`

   `git merge upstream/master`

   `git push`

7. Build the VTKExamples

   `cd VTKExamples`

   `cd build`

   `cmake -DVTK_DIR:PATH=YOUR_VTK_BIN_DIR -DBUILD_TESTING:BOOL=ON ..`

   `make`

   where YOUR_VTK_BIN_DIR is the location of your VTK build.

### Add the example

#### Choose a Topic

The examples are organized by topic. Current topics include Animation, DataStructures, Filters, GeometricObjects, Images, Meshes, etc.

#### Write the source

Note: Steps 4, 5 and 7 are applicable to C++. For Python, Java and C# see the steps in the section Steps for Python, Java and C#.

1. Create a branch in your repository

   `git checkout -b MyNewExample`

   where MyNewExample is the name of your new example.

2. Check the:

   - Cxx available snippets.
   - Python available snippets.
   - Java available snippets.

3. Save your source code in VTKExamples/src/LANGUAGE/TOPIC/

   where LANGUAGE is Cxx, Python, CSharp or Java.

   and TOPIC is the topic that you have chosen.

4. Build and test your example (NOTE: only for cxx examples)

5. for Cxx

       ```
       cd VTKExamples/build
       ```

       ```
       cmake ..
       ```

       ```
       make
       ```

       ```
       ctest -V -R MyNewExample
       ```

       Note: If **MyNewExample** is not built, then in the directory where you put the file do:

       ```
       touch CMakeLists.txt
       ```

6. If your C++ example does any rendering, the test will fail the first time and create an image in VTKExamples/build/Testing/Temporary. The image will be called TestMyNewExample.png.

7. Copy the image into: VTKExamples/src/Testing/Baseline/LANG/TOPIC/. For python and other languages, create an image with the proper name using a screen capture and copy that image into the proper location.

8. Rerun ctest and the test should pass.

#### Steps for Python, Java and C

If you are basing your code on a Cxx example use the same name as the Cxx example. This insures that cross-referencing works.

Keep the same directory structure as that in Cxx.

- Follow steps 1-3 above.
- Manually create a test image if your example does any rendering. The image should be called TestMyNewExample.png.

The following snippets can be used to write the image out:

- WriteImage for Python

- WriteImage for Java

- Then follow step 6 above

#### Add the example to the language page.

Depending on the language of your example, edit the file Cxx.md, Python.md, CSharp.md, or Java.md.

Find the section for your topic and add a line for your new example. The format of the line is:

[MyNewExample]\(/**LANG**/**TOPIC**/**MyNewExample**\) | doxygen | short description

where LANG is one of Cxx, Python, CSharp, Java.

#### Commit your changes to your topic branch

    git add MyNewExample.cxx

and if you have a baseline image,

    git add Testing/Baseline/LANG/TOPIC/TestMyNewExample.png

    git commit

#### Push the changes to github

    git push origin MyNewExample

#### Go to your github project and generate a pull request.

### Advanced usage

#### Add a description

If your example could benefit from an extended description, you can create a file MyNewExample.md. Store the file along side your source code. Use markdown to format the description.

#### Add arguments to the test

If your example requires arguments, you will need to edit the CMakeLists.txt in the topic directory.

1. Add the name of your example to the NEEDS_ARGS variable

2. Add an ADD_TEST line. See other CMakeLists.txt files for examples.

#### Add extra files to a C++ example

Most C++ examples consist of one file. If other files are required, place them in the same directory as the example. Then add a file with the same prefix as the example name and a .extras suffix. List each extra filename in the .extras file, one filename per line.

Warning

If you add extra files to the example, but do not add their filenames to the .extras file, they will appear in the left hand file menus and will not be included in the tar file for the example.

#### Review changes in a browser

If you want to preview your changes in a browser (NOTE: You must have python installed on your system)

1. Install the markdown package for python. Go here

2. Install the material theme for markdown. Go here.

3. Sync your site with your repository

   `./src/SyncSiteWithRepo.sh https::/github.com/**YOUR_NAME**/VTKExamples`

4. After a few minutes go to https://YOUR_NAME.github.io/VTKExamples/ to see your changes before issuing your pull request.