MAKEPLUGIN

How to make a function plugin

You can make function plugins by yourself to define new function
to draw by qfract.

First, you need to include plugin.h in the source directory.
Classes and functions like Point, Parameter, PluginInfo are defined
under QFract namespace, so I recommend to add

using namespace QFract;

rather than use QFract::Point and so on.

A plugin consists of the following 5 functions.
class Point consists of double x, y as public variables.
It corresponds to a point (x,y) in the plane.
(It is defined in double.h, included from plugin.h.)

To load those functions, qfract uses dlfcn.h.
Function overload for C++ causes a problem with dynamic loading,
so you should avoid it by putting definitions in
extern "C"{ }
(note that you can use C++ code in it).

i) int iter(Point z, double *param, int max)

To determine the color for each pixel.
It returns the color for the Point z.
The color is the return value (int) % 256.

If it returns -1, then the point is colored in black.

Usually, for a given Point z, this function calculates
the forward orbit up to max times and check if the termination condition
is satisfied, and return the time when the termination condition is first
satisfied, or -1 if the termination condition is not satisfied.

ii) Point map(Point z, Point c, double *param)

It is used to calculate forward orbit.
For a given Point z, it calculates the next point.
Basically it is just the process in the loop of the function iter();

iii) Point init(Point c, double *param)

This is also used to calculate forward orbit.
It returns the initial value for the Point c.
Usually it returns c itself for phase spaces, and a critical point
for parameter spaces.

iv) void paraminit(Parameter param)

This function is called when the Parameter is set or changed.
Usually for calculating global parameters.
Such a calculation often causes a use of static variables,
hence it can cause a problem in opening several windows.

You do not need to define this function.

v) PluginInfo* getInfo()

PluginInfo is a class defined in plugin.h.
It consists of:
- the name of the plugin (const char *name),
- the region in the plane to draw (double xleft, ytop, xright, ybottom),
- the number of maximal iteration (int maxiter),
- the number of forward orbit (int maxorbit),
- the number of parameters (int paramnum),
- the initial parameters (double *param),
- the filename of the child plugin (const char *childname),
- the filename of the default colormap (const char *colormap),
- the list of the descriptions for the parameters (const char** paramdesc).

You only need to do as follows:

return new PluginInfo(name, xleft, ytop, xright, ybottom, maxiter,
                      maxorbit, paramnum, param, childname,
		       colormap, paramdesc)

You can omit colormap and paramdesc (you can also omit only one of them).