Damage(3U) InterViews Reference Manual Damage(3U)
Damage - repairs damaged graphics
Damage objects store damaged areas of a graphic for subsequent incremental repair. Areas of a graphic are "damaged" if they need to be
redrawn for any reason, e.g., if their state has been modified or if under/overlapping graphics change their appearance. Damage objects
try to minimize the amount of redrawing needed to repair a graphic. They are most useful when the graphic is complicated enough that it
would be undesirable to redraw the entire canvas when the graphic is modified. Damage objects do not eliminate the need for an interac-
tor's Redraw member function, though they could be used to implement it.
Damage(Canvas* = nil, Painter* = nil, Graphic* = nil)
Create a new Damage object for a graphic on the given canvas. The painter is used to erase damaged areas using its ClearRect func-
tion prior to redrawing them.
virtual void Incur(Graphic*)
virtual void Incur(BoxObj&)
virtual void Incur(
Coord left, Coord bottom, Coord right, Coord top
Notify the damage object that a rectangular area has been damaged, either by passing the graphic that contributed the area or the
virtual void Added(Graphic*)
Notify the damage object that the given graphic was appended (not inserted) to the graphic but never drawn. The damage object can
thus be responsible for drawing newly added graphics as well.
virtual void Repair()
Repair all damage incurred since the last Repair (or since the damage object was created if this is the first Repair).
virtual void Reset()
Reset the damage object. Any damage incurred is lost.
virtual boolean Incurred()
Returns true if any damage has been incurred.
Set and get attributes of the damage object.
A helper function that returns the area in square pixels occupied by the given BoxObj.
virtual void DrawAreas()
virtual void DrawAdditions()
Explicitly draw the areas of incurred and added damage, respectively.
virtual void Merge(BoxObj&)
Merge the given BoxObj into the list of incur-damaged areas, coalescing it into an existing area if the number of non-overlapping
areas exceeds 2.
Operations for iterating over the lists of damaged areas (represented with BoxObj objects) and added Graphics. FirstArea and
FirstAddition initialize the iterator to point to the first item on the corresponding list, Next advances the iterator, and Done
returns true if the iterator points beyond the end of the list. GetArea and GetAddition return the BoxObj or Graphic to which the
A helper function for returning the UList to which an iterator points. The _areas protected member is a UList that stores the list
of damaged areas, and the _additions protected stores the list of added graphics.
DeleteArea is a helper function for deleting the storage associated with a damaged area, including the area itself and the UList
element. DeleteAreas is a helper function that deletes the list of damaged areas.
Canvas(3I), Graphic(3U), Iterator(3U), Painter(3I), UList(3U), geomobjs(3U)
Unidraw 30 January 1991 Damage(3U)