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236 lines
14 KiB
236 lines
14 KiB
14 years ago
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/src/canvas/qcanvas.cpp:3725 -->
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QCanvasPolygonalItem Class Reference<br><small>[<a href="canvas.html">canvas module</a>]</small></h1>
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<p>The QCanvasPolygonalItem class provides a polygonal canvas item
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on a QCanvas.
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<a href="#details">More...</a>
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<p><tt>#include <<a href="qcanvas-h.html">qcanvas.h</a>></tt>
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<p>Inherits <a href="qcanvasitem.html">QCanvasItem</a>.
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<p>Inherited by <a href="qcanvasrectangle.html">QCanvasRectangle</a>, <a href="qcanvaspolygon.html">QCanvasPolygon</a>, <a href="qcanvasline.html">QCanvasLine</a>, and <a href="qcanvasellipse.html">QCanvasEllipse</a>.
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<p><a href="qcanvaspolygonalitem-members.html">List of all member functions.</a>
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<h2>Public Members</h2>
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<ul>
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<li class=fn><a href="#QCanvasPolygonalItem"><b>QCanvasPolygonalItem</b></a> ( QCanvas * canvas )</li>
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<li class=fn>virtual <a href="#~QCanvasPolygonalItem"><b>~QCanvasPolygonalItem</b></a> ()</li>
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<li class=fn>virtual void <a href="#setPen"><b>setPen</b></a> ( QPen p )</li>
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<li class=fn>virtual void <a href="#setBrush"><b>setBrush</b></a> ( QBrush b )</li>
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<li class=fn>QPen <a href="#pen"><b>pen</b></a> () const</li>
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<li class=fn>QBrush <a href="#brush"><b>brush</b></a> () const</li>
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<li class=fn>virtual QPointArray <a href="#areaPoints"><b>areaPoints</b></a> () const = 0</li>
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<li class=fn>virtual QPointArray <a href="#areaPointsAdvanced"><b>areaPointsAdvanced</b></a> () const</li>
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<li class=fn>virtual QRect <a href="#boundingRect"><b>boundingRect</b></a> () const</li>
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<li class=fn>virtual int <a href="#rtti"><b>rtti</b></a> () const</li>
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</ul>
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<h2>Protected Members</h2>
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<ul>
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<li class=fn>virtual void <a href="#draw"><b>draw</b></a> ( QPainter & p )</li>
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<li class=fn>virtual void <a href="#drawShape"><b>drawShape</b></a> ( QPainter & p ) = 0</li>
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<li class=fn>bool <a href="#winding"><b>winding</b></a> () const</li>
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<li class=fn>void <a href="#setWinding"><b>setWinding</b></a> ( bool enable )</li>
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<li class=fn>void <a href="#invalidate"><b>invalidate</b></a> ()</li>
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<li class=fn>bool <a href="#isValid"><b>isValid</b></a> () const</li>
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</ul>
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<hr><a name="details"></a><h2>Detailed Description</h2>
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The QCanvasPolygonalItem class provides a polygonal canvas item
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on a <a href="qcanvas.html">QCanvas</a>.
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<p>
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<p> The mostly rectangular classes, such as <a href="qcanvassprite.html">QCanvasSprite</a> and
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<a href="qcanvastext.html">QCanvasText</a>, use the object's bounding rectangle for movement,
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repainting and collision calculations. For most other items, the
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bounding rectangle can be far too large -- a diagonal line being
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the worst case, and there are many other cases which are also bad.
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QCanvasPolygonalItem provides polygon-based bounding rectangle
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handling, etc., which is much faster for non-rectangular items.
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<p> Derived classes should try to define as small an area as possible
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to maximize efficiency, but the polygon must <em>definitely</em> be
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contained completely within the polygonal area. Calculating the
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exact requirements is usually difficult, but if you allow a small
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overestimate it can be easy and quick, while still getting almost
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all of QCanvasPolygonalItem's speed.
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<p> Note that all subclasses <em>must</em> call <a href="qcanvasitem.html#hide">hide</a>() in their destructor
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since hide() needs to be able to access <a href="#areaPoints">areaPoints</a>().
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<p> Normally, QCanvasPolygonalItem uses the odd-even algorithm for
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determining whether an object intersects this object. You can
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change this to the winding algorithm using <a href="#setWinding">setWinding</a>().
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<p> The bounding rectangle is available using <a href="#boundingRect">boundingRect</a>(). The
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points bounding the polygonal item are retrieved with
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areaPoints(). Use <a href="#areaPointsAdvanced">areaPointsAdvanced</a>() to retrieve the bounding
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points the polygonal item <em>will</em> have after
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<a href="qcanvasitem.html#advance">QCanvasItem::advance</a>(1) has been called.
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<p> If the shape of the polygonal item is about to change while the
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item is visible, call <a href="#invalidate">invalidate</a>() before updating with a
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different result from <a href="#areaPoints">areaPoints</a>().
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<p> By default, QCanvasPolygonalItem objects have a black pen and no
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brush (the default <a href="qpen.html">QPen</a> and <a href="qbrush.html">QBrush</a> constructors). You can change
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this with <a href="#setPen">setPen</a>() and <a href="#setBrush">setBrush</a>(), but note that some
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QCanvasPolygonalItem subclasses only use the brush, ignoring the
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pen setting.
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<p> The polygonal item can be drawn on a painter with <a href="#draw">draw</a>().
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Subclasses must reimplement <a href="#drawShape">drawShape</a>() to draw themselves.
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<p> Like any other canvas item polygonal items can be moved with
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<a href="qcanvasitem.html#move">QCanvasItem::move</a>() and <a href="qcanvasitem.html#moveBy">QCanvasItem::moveBy</a>(), or by setting coordinates
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with <a href="qcanvasitem.html#setX">QCanvasItem::setX</a>(), <a href="qcanvasitem.html#setY">QCanvasItem::setY</a>() and <a href="qcanvasitem.html#setZ">QCanvasItem::setZ</a>().
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<p> <p>See also <a href="graphics.html">Graphics Classes</a> and <a href="images.html">Image Processing Classes</a>.
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<hr><h2>Member Function Documentation</h2>
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<h3 class=fn><a name="QCanvasPolygonalItem"></a>QCanvasPolygonalItem::QCanvasPolygonalItem ( <a href="qcanvas.html">QCanvas</a> * canvas )
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</h3>
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Constructs a QCanvasPolygonalItem on the canvas <em>canvas</em>.
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<h3 class=fn><a name="~QCanvasPolygonalItem"></a>QCanvasPolygonalItem::~QCanvasPolygonalItem ()<tt> [virtual]</tt>
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</h3>
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Note that all subclasses <em>must</em> call <a href="qcanvasitem.html#hide">hide</a>() in their destructor
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since hide() needs to be able to access <a href="#areaPoints">areaPoints</a>().
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<h3 class=fn><a href="qpointarray.html">QPointArray</a> <a name="areaPoints"></a>QCanvasPolygonalItem::areaPoints () const<tt> [pure virtual]</tt>
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</h3>
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<p> This function must be reimplemented by subclasses. It <em>must</em>
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return the points bounding (i.e. outside and not touching) the
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shape or drawing errors will occur.
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<p>Reimplemented in <a href="qcanvaspolygon.html#areaPoints">QCanvasPolygon</a>.
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<h3 class=fn><a href="qpointarray.html">QPointArray</a> <a name="areaPointsAdvanced"></a>QCanvasPolygonalItem::areaPointsAdvanced () const<tt> [virtual]</tt>
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</h3>
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Returns the points the polygonal item <em>will</em> have after
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<a href="qcanvasitem.html#advance">QCanvasItem::advance</a>(1) is called, i.e. what the points are when
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advanced by the current <a href="qcanvasitem.html#xVelocity">xVelocity</a>() and <a href="qcanvasitem.html#yVelocity">yVelocity</a>().
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<h3 class=fn><a href="qrect.html">QRect</a> <a name="boundingRect"></a>QCanvasPolygonalItem::boundingRect () const<tt> [virtual]</tt>
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</h3>
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Returns the bounding rectangle of the polygonal item, based on
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<a href="#areaPoints">areaPoints</a>().
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<p>Reimplemented from <a href="qcanvasitem.html#boundingRect">QCanvasItem</a>.
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<h3 class=fn><a href="qbrush.html">QBrush</a> <a name="brush"></a>QCanvasPolygonalItem::brush () const
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</h3>
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<p> Returns the <a href="qbrush.html">QBrush</a> used to fill the item, if filled.
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<p> <p>See also <a href="#setBrush">setBrush</a>().
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<h3 class=fn>void <a name="draw"></a>QCanvasPolygonalItem::draw ( <a href="qpainter.html">QPainter</a> & p )<tt> [virtual protected]</tt>
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</h3>
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Reimplemented from <a href="qcanvasitem.html">QCanvasItem</a>, this draws the polygonal item by
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setting the pen and brush for the item on the painter <em>p</em> and
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calling <a href="#drawShape">drawShape</a>().
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<p>Reimplemented from <a href="qcanvasitem.html#draw">QCanvasItem</a>.
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<h3 class=fn>void <a name="drawShape"></a>QCanvasPolygonalItem::drawShape ( <a href="qpainter.html">QPainter</a> & p )<tt> [pure virtual protected]</tt>
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</h3>
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<p> Subclasses must reimplement this function to draw their shape. The
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pen and brush of <em>p</em> are already set to <a href="#pen">pen</a>() and <a href="#brush">brush</a>() prior
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to calling this function.
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<p> <b>Warning:</b> When you reimplement this function, make sure that you
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leave the painter in the same state as you found it. For example,
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if you start by calling <a href="qpainter.html#translate">QPainter::translate</a>(50, 50), end your
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code by calling QPainter::translate(-50, -50). Be also aware that
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the painter might already have some transformations set (i.e.,
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don't call <a href="qpainter.html#resetXForm">QPainter::resetXForm</a>() when you're done).
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<p> <p>See also <a href="#draw">draw</a>().
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<p>Reimplemented in <a href="qcanvasrectangle.html#drawShape">QCanvasRectangle</a>, <a href="qcanvaspolygon.html#drawShape">QCanvasPolygon</a>, and <a href="qcanvasellipse.html#drawShape">QCanvasEllipse</a>.
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<h3 class=fn>void <a name="invalidate"></a>QCanvasPolygonalItem::invalidate ()<tt> [protected]</tt>
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</h3>
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Invalidates all information about the area covered by the canvas
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item. The item will be updated automatically on the next call that
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changes the item's status, for example, <a href="qcanvasitem.html#move">move</a>() or <a href="qcanvasitem.html#update">update</a>(). Call
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this function if you are going to change the shape of the item (as
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returned by <a href="#areaPoints">areaPoints</a>()) while the item is visible.
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<h3 class=fn>bool <a name="isValid"></a>QCanvasPolygonalItem::isValid () const<tt> [protected]</tt>
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</h3>
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<p> Returns TRUE if the polygonal item's area information has not been
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invalidated; otherwise returns FALSE.
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<p> <p>See also <a href="#invalidate">invalidate</a>().
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<h3 class=fn><a href="qpen.html">QPen</a> <a name="pen"></a>QCanvasPolygonalItem::pen () const
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</h3>
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<p> Returns the <a href="qpen.html">QPen</a> used to draw the outline of the item, if any.
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<p> <p>See also <a href="#setPen">setPen</a>().
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<h3 class=fn>int <a name="rtti"></a>QCanvasPolygonalItem::rtti () const<tt> [virtual]</tt>
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</h3>
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Returns 2 (QCanvasItem::Rtti_PolygonalItem).
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<p> <p>See also <a href="qcanvasitem.html#rtti">QCanvasItem::rtti</a>().
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<p>Reimplemented from <a href="qcanvasitem.html#rtti">QCanvasItem</a>.
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<p>Reimplemented in <a href="qcanvasrectangle.html#rtti">QCanvasRectangle</a>, <a href="qcanvaspolygon.html#rtti">QCanvasPolygon</a>, <a href="qcanvasline.html#rtti">QCanvasLine</a>, and <a href="qcanvasellipse.html#rtti">QCanvasEllipse</a>.
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<h3 class=fn>void <a name="setBrush"></a>QCanvasPolygonalItem::setBrush ( <a href="qbrush.html">QBrush</a> b )<tt> [virtual]</tt>
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</h3>
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Sets the <a href="qbrush.html">QBrush</a> used when drawing the polygonal item to the brush <em>b</em>.
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<p> <p>See also <a href="#setPen">setPen</a>(), <a href="#brush">brush</a>(), and <a href="#drawShape">drawShape</a>().
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<p>Examples: <a href="canvas-example.html#x2923">canvas/canvas.cpp</a> and <a href="tutorial2-06.html#x2572">chart/chartform_canvas.cpp</a>.
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<h3 class=fn>void <a name="setPen"></a>QCanvasPolygonalItem::setPen ( <a href="qpen.html">QPen</a> p )<tt> [virtual]</tt>
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</h3>
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Sets the <a href="qpen.html">QPen</a> used when drawing the item to the pen <em>p</em>.
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Note that many QCanvasPolygonalItems do not use the pen value.
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<p> <p>See also <a href="#setBrush">setBrush</a>(), <a href="#pen">pen</a>(), and <a href="#drawShape">drawShape</a>().
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<p>Examples: <a href="canvas-example.html#x2924">canvas/canvas.cpp</a> and <a href="tutorial2-06.html#x2573">chart/chartform_canvas.cpp</a>.
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<h3 class=fn>void <a name="setWinding"></a>QCanvasPolygonalItem::setWinding ( bool enable )<tt> [protected]</tt>
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</h3>
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If <em>enable</em> is TRUE, the polygonal item will use the winding
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algorithm to determine the "inside" of the polygon; otherwise the
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odd-even algorithm will be used.
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<p> The default is to use the odd-even algorithm.
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<p> <p>See also <a href="#winding">winding</a>().
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<h3 class=fn>bool <a name="winding"></a>QCanvasPolygonalItem::winding () const<tt> [protected]</tt>
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</h3>
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Returns TRUE if the polygonal item uses the winding algorithm to
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determine the "inside" of the polygon. Returns FALSE if it uses
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the odd-even algorithm.
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<p> The default is to use the odd-even algorithm.
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<p> <p>See also <a href="#setWinding">setWinding</a>().
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<!-- eof -->
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<hr><p>
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This file is part of the <a href="index.html">Qt toolkit</a>.
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Copyright © 1995-2007
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<a href="http://www.trolltech.com/">Trolltech</a>. All Rights Reserved.<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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</html>
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