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 interactor's Redraw
member function, though they could be used
to implement it.
- Damage(Canvas* = nil, Painter* = nil, Graphic* =
- Create a new Damage object for a graphic on the given
canvas. The painter is used to erase damaged areas using its ClearRect
function prior to redrawing them.
- virtual void Incur(Graphic*)
- virtual void Incur(BoxObj&)
- virtual void Incur(
- Coord left, Coord bottom, Coord right, Coord
Notify the damage object that a rectangular area has been damaged, either by
passing the graphic that contributed the area or the area itself.
- 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
- 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.
- void SetCanvas(Canvas*)
- void SetPainter(Painter*)
- void SetGraphic(Graphic*)
- Canvas* GetCanvas()
- Painter* GetPainter()
- Graphic* GetGraphic()
- Set and get attributes of the damage object.
- int Area(BoxObj&)
- 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,
- 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.
- void FirstArea(Iterator&)
- void FirstAddition(Iterator&)
- void Next(Iterator&)
- boolean Done(Iterator)
- BoxObj* GetArea(Iterator)
- Graphic* GetAddition(Iterator)
- 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 iterator points.
- UList* Elem(Iterator)
- 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.
- void DeleteArea(BoxObj*)
- void DeleteAreas()
- 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
Canvas(3I), Graphic(3U), Iterator(3U), Painter(3I), UList(3U),