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+<title>eric4.Graphics.AssociationItem</title>
+<style>
+body {
+ background:white;
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+}
+
+h1 { color: white; background: #4FA4FF; }
+h2 { color: white; background: #4FA4FF; }
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+<body><a NAME="top" ID="top"></a>
+<h1>eric4.Graphics.AssociationItem</h1>
+<p>
+Module implementing a graphics item for an association between two items.
+</p>
+<h3>Global Attributes</h3>
+<table>
+<tr><td>Center</td></tr><tr><td>East</td></tr><tr><td>Generalisation</td></tr><tr><td>Imports</td></tr><tr><td>NoRegion</td></tr><tr><td>Normal</td></tr><tr><td>North</td></tr><tr><td>NorthEast</td></tr><tr><td>NorthWest</td></tr><tr><td>South</td></tr><tr><td>SouthEast</td></tr><tr><td>SouthWest</td></tr><tr><td>West</td></tr>
+</table>
+<h3>Classes</h3>
+<table>
+<tr>
+<td><a href="#AssociationItem">AssociationItem</a></td>
+<td>Class implementing a graphics item for an association between two items.</td>
+</tr>
+</table>
+<h3>Functions</h3>
+<table>
+<tr><td>None</td></tr>
+</table>
+<hr /><hr />
+<a NAME="AssociationItem" ID="AssociationItem"></a>
+<h2>AssociationItem</h2>
+<p>
+ Class implementing a graphics item for an association between two items.
+</p><p>
+ The association is drawn as an arrow starting at the first items and
+ ending at the second.
+</p>
+<h3>Derived from</h3>
+E4ArrowItem
+<h3>Class Attributes</h3>
+<table>
+<tr><td>None</td></tr>
+</table>
+<h3>Methods</h3>
+<table>
+<tr>
+<td><a href="#AssociationItem.__init__">AssociationItem</a></td>
+<td>Constructor</td>
+</tr><tr>
+<td><a href="#AssociationItem.__calculateEndingPoints_center">__calculateEndingPoints_center</a></td>
+<td>Private method to calculate the ending points of the association item.</td>
+</tr><tr>
+<td><a href="#AssociationItem.__calculateEndingPoints_rectangle">__calculateEndingPoints_rectangle</a></td>
+<td>Private method to calculate the ending points of the association item.</td>
+</tr><tr>
+<td><a href="#AssociationItem.__findIntersection">__findIntersection</a></td>
+<td>Method to calculate the intersection point of two lines.</td>
+</tr><tr>
+<td><a href="#AssociationItem.__findPointRegion">__findPointRegion</a></td>
+<td>Private method to find out, which region of rectangle rect contains the point (PosX, PosY) and returns the region number.</td>
+</tr><tr>
+<td><a href="#AssociationItem.__findRectIntersectionPoint">__findRectIntersectionPoint</a></td>
+<td>Private method to find the intersetion point of a line with a rectangle.</td>
+</tr><tr>
+<td><a href="#AssociationItem.__mapRectFromItem">__mapRectFromItem</a></td>
+<td>Private method to map item's rectangle to this item's coordinate system.</td>
+</tr><tr>
+<td><a href="#AssociationItem.__updateEndPoint">__updateEndPoint</a></td>
+<td>Private method to update an endpoint.</td>
+</tr><tr>
+<td><a href="#AssociationItem.unassociate">unassociate</a></td>
+<td>Public method to unassociate from the widgets.</td>
+</tr><tr>
+<td><a href="#AssociationItem.widgetMoved">widgetMoved</a></td>
+<td>Public method to recalculate the association after a widget was moved.</td>
+</tr>
+</table>
+<a NAME="AssociationItem.__init__" ID="AssociationItem.__init__"></a>
+<h4>AssociationItem (Constructor)</h4>
+<b>AssociationItem</b>(<i>itemA, itemB, type = Normal, parent = None</i>)
+<p>
+ Constructor
+</p><dl>
+<dt><i>itemA</i></dt>
+<dd>
+first widget of the association
+</dd><dt><i>itemB</i></dt>
+<dd>
+second widget of the association
+</dd><dt><i>type</i></dt>
+<dd>
+type of the association. This must be one of
+ <ul>
+ <li>Normal (default)</li>
+ <li>Generalisation</li>
+ <li>Imports</li>
+ </ul>
+</dd><dt><i>parent=</i></dt>
+<dd>
+reference to the parent object (QGraphicsItem)
+</dd>
+</dl><a NAME="AssociationItem.__calculateEndingPoints_center" ID="AssociationItem.__calculateEndingPoints_center"></a>
+<h4>AssociationItem.__calculateEndingPoints_center</h4>
+<b>__calculateEndingPoints_center</b>(<i></i>)
+<p>
+ Private method to calculate the ending points of the association item.
+</p><p>
+ The ending points are calculated from the centers of the
+ two associated items.
+</p><a NAME="AssociationItem.__calculateEndingPoints_rectangle" ID="AssociationItem.__calculateEndingPoints_rectangle"></a>
+<h4>AssociationItem.__calculateEndingPoints_rectangle</h4>
+<b>__calculateEndingPoints_rectangle</b>(<i></i>)
+<p>
+ Private method to calculate the ending points of the association item.
+</p><p>
+ The ending points are calculated by the following method.
+</p><p>
+ For each item the diagram is divided in four Regions by its diagonals
+ as indicated below
+ <pre>
+ \ Region 2 /
+ \ /
+ |--------|
+ | \ / |
+ | \ / |
+ | \/ |
+ Region 1 | /\ | Region 3
+ | / \ |
+ | / \ |
+ |--------|
+ / \
+ / Region 4 \
+ </pre>
+</p><p>
+ Each diagonal is defined by two corners of the bounding rectangle
+</p><p>
+ To calculate the start point we have to find out in which
+ region (defined by itemA's diagonals) is itemB's TopLeft corner
+ (lets call it region M). After that the start point will be
+ the middle point of rectangle's side contained in region M.
+</p><p>
+ To calculate the end point we repeat the above but in the opposite direction
+ (from itemB to itemA)
+</p><a NAME="AssociationItem.__findIntersection" ID="AssociationItem.__findIntersection"></a>
+<h4>AssociationItem.__findIntersection</h4>
+<b>__findIntersection</b>(<i>p1, p2, p3, p4</i>)
+<p>
+ Method to calculate the intersection point of two lines.
+</p><p>
+ The first line is determined by the points p1 and p2, the second
+ line by p3 and p4. If the intersection point is not contained in
+ the segment p1p2, then it returns (-1.0, -1.0).
+</p><p>
+ For the function's internal calculations remember:<br />
+ QT coordinates start with the point (0,0) as the topleft corner
+ and x-values increase from left to right and y-values increase
+ from top to bottom; it means the visible area is quadrant I in
+ the regular XY coordinate system
+</p><p>
+ <pre>
+ Quadrant II | Quadrant I
+ -----------------|-----------------
+ Quadrant III | Quadrant IV
+ </pre>
+</p><p>
+ In order for the linear function calculations to work in this method
+ we must switch x and y values (x values become y values and viceversa)
+</p><dl>
+<dt><i>p1</i></dt>
+<dd>
+first point of first line (QPointF)
+</dd><dt><i>p2</i></dt>
+<dd>
+second point of first line (QPointF)
+</dd><dt><i>p3</i></dt>
+<dd>
+first point of second line (QPointF)
+</dd><dt><i>p4</i></dt>
+<dd>
+second point of second line (QPointF)
+</dd>
+</dl><dl>
+<dt>Returns:</dt>
+<dd>
+the intersection point (QPointF)
+</dd>
+</dl><a NAME="AssociationItem.__findPointRegion" ID="AssociationItem.__findPointRegion"></a>
+<h4>AssociationItem.__findPointRegion</h4>
+<b>__findPointRegion</b>(<i>rect, posX, posY</i>)
+<p>
+ Private method to find out, which region of rectangle rect contains the point
+ (PosX, PosY) and returns the region number.
+</p><dl>
+<dt><i>rect</i></dt>
+<dd>
+rectangle to calculate the region for (QRectF)
+</dd><dt><i>posX</i></dt>
+<dd>
+x position of point (float)
+</dd><dt><i>posY</i></dt>
+<dd>
+y position of point (float)
+</dd>
+</dl><dl>
+<dt>Returns:</dt>
+<dd>
+the calculated region number<br />
+ West = Region 1<br />
+ North = Region 2<br />
+ East = Region 3<br />
+ South = Region 4<br />
+ NorthWest = On diagonal 2 between Region 1 and 2<br />
+ NorthEast = On diagonal 1 between Region 2 and 3<br />
+ SouthEast = On diagonal 2 between Region 3 and 4<br />
+ SouthWest = On diagonal 1 between Region4 and 1<br />
+ Center = On diagonal 1 and On diagonal 2 (the center)<br />
+</dd>
+</dl><a NAME="AssociationItem.__findRectIntersectionPoint" ID="AssociationItem.__findRectIntersectionPoint"></a>
+<h4>AssociationItem.__findRectIntersectionPoint</h4>
+<b>__findRectIntersectionPoint</b>(<i>item, p1, p2</i>)
+<p>
+ Private method to find the intersetion point of a line with a rectangle.
+</p><dl>
+<dt><i>item</i></dt>
+<dd>
+item to check against
+</dd><dt><i>p1</i></dt>
+<dd>
+first point of the line (QPointF)
+</dd><dt><i>p2</i></dt>
+<dd>
+second point of the line (QPointF)
+</dd>
+</dl><dl>
+<dt>Returns:</dt>
+<dd>
+the intersection point (QPointF)
+</dd>
+</dl><a NAME="AssociationItem.__mapRectFromItem" ID="AssociationItem.__mapRectFromItem"></a>
+<h4>AssociationItem.__mapRectFromItem</h4>
+<b>__mapRectFromItem</b>(<i>item</i>)
+<p>
+ Private method to map item's rectangle to this item's coordinate system.
+</p><dl>
+<dt><i>item</i></dt>
+<dd>
+reference to the item to be mapped (QGraphicsRectItem)
+</dd>
+</dl><dl>
+<dt>Returns:</dt>
+<dd>
+item's rectangle in local coordinates (QRectF)
+</dd>
+</dl><a NAME="AssociationItem.__updateEndPoint" ID="AssociationItem.__updateEndPoint"></a>
+<h4>AssociationItem.__updateEndPoint</h4>
+<b>__updateEndPoint</b>(<i>region, isWidgetA</i>)
+<p>
+ Private method to update an endpoint.
+</p><dl>
+<dt><i>region</i></dt>
+<dd>
+the region for the endpoint (integer)
+</dd><dt><i>isWidgetA</i></dt>
+<dd>
+flag indicating update for itemA is done (boolean)
+</dd>
+</dl><a NAME="AssociationItem.unassociate" ID="AssociationItem.unassociate"></a>
+<h4>AssociationItem.unassociate</h4>
+<b>unassociate</b>(<i></i>)
+<p>
+ Public method to unassociate from the widgets.
+</p><a NAME="AssociationItem.widgetMoved" ID="AssociationItem.widgetMoved"></a>
+<h4>AssociationItem.widgetMoved</h4>
+<b>widgetMoved</b>(<i></i>)
+<p>
+ Public method to recalculate the association after a widget was moved.
+</p>
+<div align="right"><a href="#top">Up</a></div>
+<hr />
+</body></html>
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