coding style guideline

ViSP coding style guideline

Files

• Each class has its own header and implementation file
• A template class has only a header file
• The file name should match the class name
• C++ interface headers have .h extension
• Implementation files have .cpp extension
• As an example, if the class is named vpMyNewClass, the header file name should be vpMyNewClass.h and the implementation file vpMyNewClass.cpp

File structure

Every source file starts with GPL-v2 license. Use existing code to get the template.

Other rules for both header and implementation files include:

• Code lines should not be very long. Normally, they should be limited to 120 characters.

• No tabulation should be used. Set your editor to use spaces instead. We recommend to use the provided Visual Code settings.

• Only English text is allowed. Do not put comments or string literals in other languages.

• Indentation is 2 spaces.

• Each file (.h or .cpp) should end with an empty line to avoid a compiler warning

• Each header should include visp3/core/vpConfig.h before other ViSP headers.

• Header files must use guarding macros, protecting the files from repeated inclusion:

    #ifndef VP_MY_NEW_CLASS_H
    #define VP_MY_NEW_CLASS_H
  
    #include <visp3/core/vpConfig.h>
    ...
    #endif
  

• C++ macro should be upper-case like in the previous example

Naming conventions

• Class names start with a vp prefix, then each name starts with an uppercase letter. Underscores are not allowed; ie vpMyNewClass
• Macros and enumeration constants are written with all capital letters. Words are separated by underscore. Macro should match the regular expression: ^[A-Z][A-Z0-9_]*$
• All external functions and classes must use VISP_EXPORT, otherwise there will be linking errors on Windows.
• Member or static functions start with a lowercase, then next words with an uppercase; ie vpMyNewClass::myNewMethod().

Class implementation conventions

• A class should have a default constructor, a virtual destructor and a copy operator. The header file vpMyNewClass.h should contain at least the following:

    class VISP_EXPORT vpMyNewClass
    {
    public:
      vpMyNewClass();                                       // Default constructor
      virtual ~vpMyNewClass();                              // Virtual destructor
      const vpMyNewClass& operator=(const vpMyNewClass &v); // Copy operator
      ...
    };
  

Documentation

The documentation is written in doxygen style. Use the existing documentation as example. Normally, each function/method description includes:

• a short description
• all the parameters explained; e.g. specify, which image types are accepted, what would be the recommended values for the parameter and how they affect the algorithm etc.
• the full description with short use samples, references to papers, formulas, etc

In order to avoid warnings when building with Xcode for iOS, the following style should be adopted for

• Parameter description: use doxygen \param special command to describe only one parameter:

    /*!
      \param x : Coordinates of a point along x-axis.
      \param y : Coordinates of a point along y-axis.
     */
    void myClass::myMethod(double x, double y)
  

  The following is not allowed:

    /*!
      \param x,y : Coordinates of a point.
     */
    void myClass::myMethod(double x, double y)
  

• Putting documentation after members: use doxygen ///< special character instead of //!<

    int var; ///< Value used to... 
  

Code layout

• Currently used in ViSP and recommended formatting style looks as follows:

  if (B <= A) {
    throw (vpException(vpException::badValue, "Bad gray levels with %d <= %A", B, A)) ;
  }
  unsigned char v;
  
  double factor = static_cast<double>(B_star - A_star)/static_cast<double>(B - A);
  const unsigned int width = I.getWidth(); 
  const unsigned int height = I.getHeight();
  for (unsigned int i=0 ; i < height; ++i) {
    for (unsigned int j=0 ; j < width; ++j) {
      v = I[i][j];
  
      if (v <= A) {
        I[i][j] = A_star;
      }
      else if (v >= B) {
        I[i][j] = B_star;
      }
      else {
        I[i][j] = static_cast<unsigned char>(A_star + (factor * (v - A)));
      }
    }
  }
  

• Old style cast is not allowed

  double pi = 3.1415;
  int val = (int)pi; // Not allowed
  

  Use rather a more verbose C++ cast style

  double pi = 3.1415;
  int val = static_cast<int>(pi);
  

• Identifier should be shorter or equal to 31 characters The following examples are not allowed:

  typedef enum { car, bus, truck } vpLargeTransportationVehiculeTypename; // Not allowed, type name has 37 characters
  void computeImageProcessingOnColorImage(const vpImage<vpRGBa> &I); // Not allowed, function name has 34 characters
  

  Use rather something like:

  typedef enum { car, bus, truck } vpLargeVehiculeType;
  void computeImageProcessing(const vpImage<vpRGBa> &I); 
  

• Use only one statement per line

  switch(val) {
    case 1:
      val += 1; break; // Not allowed
  }
  

  Use rather:

  switch(val) {
    case 1:
      val += 1; 
      break; 
  }
  

• A function has at least 7 parameters