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The Q3CanvasPolygonalItem class provides a polygonal canvas item on a Q3Canvas. More...
#include <Q3CanvasPolygonalItem>
This class is part of the Qt 3 support library. It is provided to keep old source code working. We strongly advise against using it in new code. See Porting to Qt 4 for more information.
This class is not part of the Qt GUI Framework Edition.
Inherits Q3CanvasItem.
Inherited by Q3CanvasEllipse, Q3CanvasLine, Q3CanvasPolygon, and 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(). Use 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().
By default, Q3CanvasPolygonalItem objects have a black pen and no brush (the default QPen and QBrush constructors). You can change this with setPen() and 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() and Q3CanvasItem::moveBy(), or by setting coordinates with Q3CanvasItem::setX(), Q3CanvasItem::setY() and Q3CanvasItem::setZ().
See also QtCanvas and Porting to Graphics View.
Constructs a Q3CanvasPolygonalItem on the canvas canvas.
Note that all subclasses must call hide() in their destructor since hide() needs to be able to access areaPoints().
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.
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() and yVelocity().
Reimplemented from Q3CanvasItem::boundingRect().
Returns the bounding rectangle of the polygonal item, based on areaPoints().
Returns the QBrush used to fill the item, if filled.
See also setBrush().
Reimplemented from Q3CanvasItem::collidesWith().
Reimplemented from Q3CanvasItem::draw().
Reimplemented from Q3CanvasItem, this draws the polygonal item by setting the pen and brush for the item on the painter p and calling drawShape().
Subclasses must reimplement this function to draw their shape. The pen and brush of p are already set to pen() and brush() prior to calling this function.
See also draw().
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() or update(). Call this function if you are going to change the shape of the item (as returned by areaPoints()) while the item is visible.
Returns true if the polygonal item's area information has not been invalidated; otherwise returns false.
See also invalidate().
Returns the QPen used to draw the outline of the item, if any.
See also setPen().
Reimplemented from Q3CanvasItem::rtti().
Returns 2 (Q3CanvasItem::Rtti_PolygonalItem).
See also Q3CanvasItem::rtti().
Sets the QBrush used when drawing the polygonal item to the brush b.
See also setPen(), brush(), and drawShape().
Sets the QPen used when drawing the item to the pen p. Note that many Q3CanvasPolygonalItems do not use the pen value.
See also setBrush(), pen(), and drawShape().
If 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.
See also winding().
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.
See also setWinding().
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