The Q3CanvasPolygonalItem class provides a polygonal canvas item on a Q3Canvas . 更多...
| 头： | #include <Q3CanvasPolygonalItem> |
| 继承： | Q3CanvasItem |
| 继承者： | Q3CanvasEllipse , Q3CanvasLine , Q3CanvasPolygon ，和 Q3CanvasRectangle |
| Q3CanvasPolygonalItem (Q3Canvas * canvas ) | |
| virtual | ~Q3CanvasPolygonalItem () |
| virtual Q3PointArray | areaPoints () const = 0 |
| virtual Q3PointArray | areaPointsAdvanced () const |
| QBrush | brush () const |
| QPen | pen () const |
| virtual void | setBrush (QBrush b ) |
| virtual void | setPen (QPen p ) |
| virtual QRect | boundingRect () const |
| virtual bool | collidesWith (const Q3CanvasItem * i ) const |
| virtual int | rtti () const |
| virtual void | drawShape (QPainter & p ) = 0 |
| void | invalidate () |
| bool | isValid () const |
| void | setWinding (bool enable ) |
| bool | winding () const |
| virtual void | draw (QPainter & p ) |
The Q3CanvasPolygonalItem class provides a polygonal canvas item on a Q3Canvas .
The mostly rectangular classes, such as Q3CanvasSprite and Q3CanvasText , use the object's bounding rectangle for movement, repainting and collision calculations. For most other items, the bounding rectangle can be far too large -- a diagonal line being the worst case, and there are many other cases which are also bad. Q3CanvasPolygonalItem provides polygon-based bounding rectangle handling, etc., which is much faster for non-rectangular items.
Derived classes should try to define as small an area as possible to maximize efficiency, but the polygon must definitely be contained completely within the polygonal area. Calculating the exact requirements is usually difficult, but if you allow a small overestimate it can be easy and quick, while still getting almost all of Q3CanvasPolygonalItem 's speed.
Note that all subclasses must call hide () in their destructor since hide () needs to be able to access areaPoints ().
Normally, Q3CanvasPolygonalItem uses the odd-even algorithm for determining whether an object intersects this object. You can change this to the winding algorithm using setWinding ().
The bounding rectangle is available using boundingRect (). The points bounding the polygonal item are retrieved with areaPoints ()。使用 areaPointsAdvanced () to retrieve the bounding points the polygonal item will have after Q3CanvasItem::advance (1) has been called.
If the shape of the polygonal item is about to change while the item is visible, call invalidate () before updating with a different result from areaPoints ().
默认情况下， Q3CanvasPolygonalItem objects have a black pen and no brush (the default QPen and QBrush constructors). You can change this with setPen () 和 setBrush (), but note that some Q3CanvasPolygonalItem subclasses only use the brush, ignoring the pen setting.
The polygonal item can be drawn on a painter with draw (). Subclasses must reimplement drawShape () to draw themselves.
Like any other canvas item polygonal items can be moved with Q3CanvasItem::move () 和 Q3CanvasItem::moveBy (), or by setting coordinates with Q3CanvasItem::setX (), Q3CanvasItem::setY () 和 Q3CanvasItem::setZ ().
另请参阅 QtCanvas and Porting to Graphics View .
构造 Q3CanvasPolygonalItem on the canvas canvas .
[虚拟]
Q3CanvasPolygonalItem::
~Q3CanvasPolygonalItem
()
Note that all subclasses must call hide () in their destructor since hide () needs to be able to access areaPoints ().
[pure virtual]
Q3PointArray
Q3CanvasPolygonalItem::
areaPoints
() const
This function must be reimplemented by subclasses. It must return the points bounding (i.e. outside and not touching) the shape or drawing errors will occur.
[虚拟]
Q3PointArray
Q3CanvasPolygonalItem::
areaPointsAdvanced
() const
Returns the points the polygonal item will have after Q3CanvasItem::advance (1) is called, i.e. what the points are when advanced by the current xVelocity () 和 yVelocity ().
[虚拟]
QRect
Q3CanvasPolygonalItem::
boundingRect
() const
重实现自 Q3CanvasItem::boundingRect ().
Returns the bounding rectangle of the polygonal item, based on areaPoints ().
返回 QBrush used to fill the item, if filled.
另请参阅 setBrush ().
[虚拟]
bool
Q3CanvasPolygonalItem::
collidesWith
(const
Q3CanvasItem
*
i
) const
重实现自 Q3CanvasItem::collidesWith ().
[virtual protected]
void
Q3CanvasPolygonalItem::
draw
(
QPainter
&
p
)
重实现自 Q3CanvasItem::draw ().
重实现自 Q3CanvasItem , this draws the polygonal item by setting the pen and brush for the item on the painter p and calling drawShape ().
[pure virtual protected]
void
Q3CanvasPolygonalItem::
drawShape
(
QPainter
&
p
)
Subclasses must reimplement this function to draw their shape. The pen and brush of p are already set to pen () 和 brush () prior to calling this function.
另请参阅 draw ().
[protected]
void
Q3CanvasPolygonalItem::
invalidate
()
Invalidates all information about the area covered by the canvas item. The item will be updated automatically on the next call that changes the item's status, for example, move () 或 update (). Call this function if you are going to change the shape of the item (as returned by areaPoints ()) while the item is visible.
[protected]
bool
Q3CanvasPolygonalItem::
isValid
() const
Returns true if the polygonal item's area information has not been invalidated; otherwise returns false.
另请参阅 invalidate ().
返回 QPen used to draw the outline of the item, if any.
另请参阅 setPen ().
[虚拟]
int
Q3CanvasPolygonalItem::
rtti
() const
重实现自 Q3CanvasItem::rtti ().
Returns 2 ( Q3CanvasItem::Rtti_PolygonalItem ).
另请参阅 Q3CanvasItem::rtti ().
[虚拟]
void
Q3CanvasPolygonalItem::
setBrush
(
QBrush
b
)
设置 QBrush used when drawing the polygonal item to the brush b .
另请参阅 setPen (), brush ()，和 drawShape ().
[虚拟]
void
Q3CanvasPolygonalItem::
setPen
(
QPen
p
)
设置 QPen used when drawing the item to the pen p . Note that many Q3CanvasPolygonalItems do not use the pen value.
另请参阅 setBrush (), pen ()，和 drawShape ().
[protected]
void
Q3CanvasPolygonalItem::
setWinding
(
bool
enable
)
若 enable is true, the polygonal item will use the winding algorithm to determine the "inside" of the polygon; otherwise the odd-even algorithm will be used.
The default is to use the odd-even algorithm.
另请参阅 winding ().
[protected]
bool
Q3CanvasPolygonalItem::
winding
() const
Returns true if the polygonal item uses the winding algorithm to determine the "inside" of the polygon. Returns false if it uses the odd-even algorithm.
The default is to use the odd-even algorithm.
另请参阅 setWinding ().