Internal Architecture

Above graphic is relationship among major objects of MadButterfly. redraw_man_t, redraw manager, is supposed to manage graphic elements, shapes, and decide when and who to redraw on the output screen.

shape_t is base-type for all graphic objects. It can be a path, a text, a ellipse, ..., or an image. When the states or attributes of an graphic object changed, managing redraw_man_t, the one that manages the graphic object, will be notified. The redraw_man_t will schedule a redrawing for every dirty objects, changed ones, and relative objects. The relative objects are objects effected by changed ones. For example, part of a relative object may be hidden before changing, but it is re-explored after chaning. The explored part of the object must be redrawed.

The shape of shape objects are vary from type to type. To simplize the problem, we use a rectangle to model the area occupied by an object. geo_t is the one used to model the rectangle. Shape objects should update associated geo_t objects to reflect changing of them-self.

coord_t is used to model transformation in coordinate system. A coord_t is actually an transform matrix with additional informations. coord_t objects are organized as a tree according hierachy of group tags in a SVG file. coord_t has a member variable, called before_pmem, that is relative position in parent coord. coord_t::before_pmem stands for "before parent member", it is an index to the list of member shapes of parent coord. Members of a coord is shape tags they are children of the "g" tag of the coord corresponding. coord_t::before_pmem means "g" of the coord is before the indexed member of parent.

It is possible to have more than one coord with the same coord_t::before_pmem value and as children of a coord. It means all children with the same coord_t::before_pmem value are all before nth member, after (n-1)th member, and they are in order of them-self in the children list.

Colors or patterns used to stroke or fill shapes are described by paint_t . Every shape object has a paint, but a paint object can be used by multiple shape objects. Once a paint is changed, all objects that associate with the paint are dirty. They will be scheduled by associated redraw_man_t object to update graphics on output screen.