Version 5.0 The LEDA User Manual

e inserted in the result scene. In the third variant the contents of the result scene will
be cleared, and then the object returned by (∗f) will be inserted in the result scene. The
class geowin update has also the following virtual functions:
bool insert(const InpObject& new)
bool del(const InpObject& new)
bool change(const InpObject& old obj , const InpObject& new obj )
where new is a new inserted or deleted object and old obj and new obj are objects before
and after a change. InpObject is the value type of the container of the input scene.
With these functions it is possible to support incremental algorithms. The functions
will be called, when in the input scene new objects are added (insert), deleted (del)
or changed when performing a move or rotate operation (change). In the base class
geowin update these functions return false. That means, that the standard updatefunction
of the update object should be used. But in derived classes it is possible to
overwrite these functions and provide user-defined update operations for these three incremental
operations. Then the function has to return true. That means, that the standard
update function of the update object should not be used. Instead the incremental
operation performs the update-operation.
It is also possible to provide user defined redraw for a scene. For this purpose we use
redraw objects derived from geowin redraw. The derived class has to overwrite the virtual
redraw function
void draw(window& W, color c1 , color c2 , double x1 , double y1 , double x2 , double y2 )
of the base class to provide a user defined redraw function. The first 3 parameters of this
function are the redraw window and the first and second drawing color (color and color2)
of the scene. The class geowin redraw has also a virtual method
bool draw container( )
that returns false in the base class. If you want the user defined redraw of the scene
(provided by the redraw function draw) and the execution of the ’normal’ redraw of
the scene as well (output of the objects stored in the container of the scene), you have
to overwrite draw container in a derived class by a function returning true. A virtual
method
bool write postscript(ps file& PS, color c1 , color c2 )
is provided for output to a LEDA postscript file PS. c1 and c2 are the first and second
drawing color (color and color2 ) of the scene. Another class that can be used for user
defined redraw is the templated class geowin redraw container. This class
has as well virtual functions for redraw and postscript output, but provides a slighly
changed interface:
bool draw(const CONTAINER& c, window& w, color c1 , color c2 ,
double, double, double, double)