A feature-rich gui for the computer algebra system maxima

What is this file about?

This is the documentation for the C++ code of wxMaxima. If you are looking on information how to use the program instead you might want to consult the online manual instead that is shipped with the program and (after compilation of the program) can be found at info/wxmaxima.html in the directory the contents of the tarball or the git repo the code is in.

What is wxMaxima?

wxMaxima is a full-featured graphical frontend for maxima, a full-featured computer algebra system that will do numeric calculations, if one wants to. But it is specialized in manipulating and solving symbolic equations.

A random screenshot of wxMaxima

How does wxMaxima work?

The main things that are important to know are:

  • Maxima is a command-line program that can use a network connection in order to communicate with a frontend.
  • In data/wxmathml.lisp wxMaxima teaches maxima to talk in a XML dialect: Maxima's normal output format is human-readable. But it can be tricked into containing strings that look like input or output labels and it doesn't guarantee that there is a way to transform output from maxima into a valid input again that has exactly the same meaning.
  • The worksheet is defined in the class Worksheet.
  • It is organized in GroupCells that each can contain a cell containing a list of cells containing a label and the user input and a list of cells containing the output label and 2d math from maxima.
  • All cells contain pointers so they can be used as a part of a double-linked list for the logical order they appear in and a second double-linked list that tells which cell to draw next. The latter is needed for handling the fact that some things (like fractions) can be displayed as 2D maths and in a more linear way.
  • For every mathematical function, image or piece of text a Cell there is a specialized MathCell type that "knows" how to draw it, how to convert it to a string or how to convert it to Mathml, OOML, RTF or any other data format wxMaxima supports. There is, for example, an AbsCell for the abs() command, an IntCell representing integrate, a ParenCell for parenthesis and a FunCell for all the functions no special handling is needed for.
  • Configuration is something like a central object keeping the configuration needed for displaying cells.

How to get documentation for the code?

  • Install Doxygen,
  • Optionally install GraphViz (it generates call graphs, inheritance graphs and caller graphs so it really makes the documentation more usable)
  • make sure these two utilities are in the search path of your system
  • cd into the Doxygen directory of the wxMaxima sources and type:

If your system is set up for compiling code and the project has already been compiled on the current system (see the file INSTALL for details) this should generate a file named index.html that will redirect to the documentation.

Where to start reading?

This naturally depends on what you want to archieve.

  • The worksheet is mostly handled by the class Worksheet
  • All the cells that are displayed in the worksheet and all the sub- cells that represent individual elements inside one of these cells are child objects of MathCell. This object also contains most of the logic that allows to connect the individual cells to a list as well as the pointers MathCell::m_previous and MathCell::m_next.
  • The undo buffer and the conversion of cells into characters for drag-and-drop or saving files are handles by the class EditorCell
  • The menus are generated by wxMaximaFrame and most of the menu actions are handled by the class wxMaxima. One of the most important concepts that are important to know is that everything that is displayed in

Things you have to know

  • C++ provides the magic that allows to attach objects of all imaginable cell types to a list of the type MathCell *
  • MathCell provides a second list (MathCell::m_nextToDraw and MathCell::m_previousToDraw that represents the order the objects are displayed in: Some things like Fractions and text contained between parenthesis might be layouted differently when they contain a line break.
  • There are several ways child objects from MathCell can form trees:
    • Some objects like sqrt() or a pair of parenthesis might contain a list.
    • Super- and subscripts are lists.
    • GroupCells allow to move their children to a separate list that isn't displayed (which enables folding of chapters).
  • Methods that operate on lists typically start processing the list from the element they were called from. This means that they only will work as expected (in other words: process the complete list) only if they are called for the first element of the list. wxMaxima currently makes sure that this requirement is met by treating the first element of a list as the list itself. Searching the first element of a given list would be simple, though:
     MathCell *ListStart=this;
     while(ListStart->m_previous) ListStart = ListStart->m_previous;

Breaking long 2D objects into lines

wxMaxima can break some 2D objects into lines if they otherwise would be longer wider than the screen.

Objects that are broken apart this way technically aren't displayed any more. Instead they add the lists of objects they contain to the list composed of m_nextToDraw. If an object isn't broken apart it is displayed itself and automatically handles displaying all of its contents.

The 2-pass layout process needed for this dynamic layout is implemented in GroupCell::BreakLines.

Naming rules

Keeping the code more or less homogenous increases the readability. In order to archieve that wxMaxima uses a few naming rules:

  • The names of member variables are prefixed with "m_" for "member".
  • The names of member functions (aka methods) are written in CamelCase.
  • The names of enums do not really matter as they are rarely used and if they are they are used in context where it is opvious that they name an enum type so there aren't any rules for the names of enums right now.