Implement orthogonal line drawing

20 files changed, 524 insertions, 121 deletions

diff --git a/src/boxsidehub.cpp b/src/boxsidehub.cpp
new file mode 100644
index 0000000..e0c0692
--- /dev/null
+++ b/src/boxsidehub.cpp
@@ -0,0 +1,140 @@
+// Copyright (C) 2008  Lukas Lalinsky
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+#include <QDebug>
+#include <QGraphicsItem>
+#include <QPair>
+#include "connector.h"
+#include "diagramobject.h"
+#include "diagramconnection.h"
+#include "boxsidehub.h"
+
+BoxSideHub::BoxSideHub(DiagramObject *owner)
+	: Hub(owner)
+{
+}
+
+enum Side {
+	Top,
+	Right,
+	Bottom,
+	Left
+};
+
+static int
+cmpAngle(qreal a, qreal b)
+{
+	qreal d = a - b;
+	if (d > 180)
+		d = d - 360;
+	else if (d < -180)
+		d = d + 360;
+	return d;
+}
+
+typedef QPair<Connector *, qreal> ConnectorRealPair;
+
+static bool
+itemLessThan(const ConnectorRealPair &a, const ConnectorRealPair &b)
+{
+	int r = cmpAngle(a.second, b.second);
+	if (r == 0) {
+		return a.first->owner() < b.first->owner();
+	}
+	return r < 0;
+}
+
+//              |
+//    180-cA    |   cA
+//    _____________________
+//              |
+//    180+cA    |   360-cA
+//              |
+
+void
+BoxSideHub::update()
+{
+	QHash<Side, QList<ConnectorRealPair> > sides;
+	DiagramObject *item = owner();
+	QRectF rect = item->boundingRect().translated(item->pos());
+	qDebug() << this;
+	foreach (Connector *connector, connectors()) {
+		DiagramConnection *connection = connector->owner();
+		Connector *connector1 = connection->connector(0);
+		Connector *connector2 = connection->connector(1);
+		DiagramObject *item1, *item2;
+		if (connector1 == connector) {
+    		item1 = item;
+    		item2 = connector2->connectedObject();
+		}
+		else {
+			item1 = item;
+			item2 = connector1->connectedObject();
+		}
+		QRectF rect1 = rect;
+		QRectF rect2 = item2->boundingRect().translated(item2->pos());
+		qreal angle = QLineF(rect1.center(), rect2.center()).angle();
+		qreal cornerAngle = QLineF(rect1.center(), rect1.topRight()).angle();
+		Side side = Right;
+		if (angle > cornerAngle) {
+			if (angle <= 180 - cornerAngle) {
+				side = Top;
+			}
+			else if (angle <= 180 + cornerAngle) {
+				side = Left;
+			}
+			else if (angle <= 360 - cornerAngle) {
+				side = Bottom;
+			}
+		}
+		qDebug() << angle << cornerAngle << side;
+		sides[side].append(qMakePair(connector, angle));
+	}
+	qDebug() << sides;
+	foreach (Side side, sides.keys()) {
+		QPointF p, dp;
+		QList<ConnectorRealPair> c = sides[side];
+		qSort(c.begin(), c.end(), itemLessThan);
+		qreal angle;
+		switch (side) {
+		case Top:
+			p = rect.topLeft();
+			dp = QPointF(rect.width() / (c.size() + 1), 0);
+			angle = 90;
+			break;
+		case Right:
+			p = rect.topRight();
+			dp = QPointF(0, rect.height() / (c.size() + 1));
+			angle = 0;
+			break;
+		case Bottom:
+			p = rect.bottomLeft();
+			dp = QPointF(rect.width() / (c.size() + 1), 0);
+			angle = 270;
+			break;
+		case Left:
+			p = rect.topLeft();
+			dp = QPointF(0, rect.height() / (c.size() + 1));
+			angle = 180;
+			break;
+		}
+		foreach (ConnectorRealPair item, c) {
+			p += dp;
+			item.first->setPos(p);
+			item.first->setAngle(angle);
+		}
+	}
+}
diff --git a/src/boxsidehub.h b/src/boxsidehub.h
new file mode 100644
index 0000000..a20e80e
--- /dev/null
+++ b/src/boxsidehub.h
@@ -0,0 +1,29 @@
+// Copyright (C) 2008  Lukas Lalinsky
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+#ifndef BOXSIDEHUB_H
+#define BOXSIDEHUB_H
+
+#include "hub.h"
+
+class BoxSideHub : public Hub
+{
+public:
+	BoxSideHub(DiagramObject *owner);
+	virtual void update();
+};
+
+#endif
diff --git a/src/commands.cpp b/src/commands.cpp
index 1ff3def..4d6a5bb 100644
--- a/src/commands.cpp
+++ b/src/commands.cpp
@@ -155,7 +155,8 @@ void
 RemoveObjectCommand::undo()
 {
 	m_document->addItem(m_object);
-	foreach (DiagramConnection *connection, m_connections)
+	foreach (DiagramConnection *connection, m_connections) {
 		m_document->addItem(connection);
+        }
 	m_owner = false;
 }
diff --git a/src/connector.cpp b/src/connector.cpp
new file mode 100644
index 0000000..6395546
--- /dev/null
+++ b/src/connector.cpp
@@ -0,0 +1,99 @@
+// Copyright (C) 2008  Lukas Lalinsky
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+#include "connector.h"
+#include "hub.h"
+#include "diagramconnection.h"
+
+Connector::Connector(DiagramConnection *owner)
+	: m_owner(owner), m_hub(NULL)
+{
+}
+
+DiagramConnection *
+Connector::owner() const
+{
+	return m_owner;
+}
+
+QPointF
+Connector::pos() const
+{
+	return m_pos;
+}
+
+void
+Connector::setPos(const QPointF &pos)
+{
+	if (m_pos != pos) {
+		m_pos = pos;
+	}
+}
+
+qreal
+Connector::angle() const
+{
+	return m_angle;
+}
+
+void
+Connector::setAngle(qreal angle)
+{
+	if (m_angle != angle) {
+		m_angle = angle;
+	}
+}
+
+Hub *
+Connector::hub() const
+{
+	return m_hub;
+}
+
+void
+Connector::setHub(Hub *hub)
+{
+    if (hub)
+        hub->removeConnector(this);
+	m_hub = hub;
+    m_hub->addConnector(this);
+}
+
+bool
+Connector::isConnected() const
+{
+	return m_hub;
+}
+
+DiagramObject *
+Connector::connectedObject() const
+{
+    if (isConnected())
+        return hub()->owner();
+    return NULL;
+}
+
+Connector *
+Connector::otherEnd() const
+{
+	DiagramConnection *conn = owner();
+	if (conn->connector(0) == this) {
+		return conn->connector(1);
+	}
+	else {
+		return conn->connector(0);
+	}
+}
diff --git a/src/connector.h b/src/connector.h
new file mode 100644
index 0000000..f1b6b74
--- /dev/null
+++ b/src/connector.h
@@ -0,0 +1,52 @@
+// Copyright (C) 2008  Lukas Lalinsky
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+#ifndef CONNECTOR_H
+#define CONNECTOR_H
+
+#include <QPointF>
+class DiagramConnection;
+class DiagramObject;
+class Hub;
+
+class Connector
+{
+public:
+	Connector(DiagramConnection *owner);
+	DiagramConnection *owner() const;
+
+	QPointF pos() const;
+	void setPos(const QPointF &pos);
+
+	qreal angle() const;
+	void setAngle(qreal angle);
+
+	bool isConnected() const;
+	DiagramObject *connectedObject() const;
+
+	Connector *otherEnd() const;
+	
+	Hub *hub() const;
+	void setHub(Hub *hub);
+
+private:
+	QPointF m_pos;
+	qreal m_angle;
+	DiagramConnection *m_owner;
+	Hub *m_hub;
+};
+
+#endif
diff --git a/src/diagramconnection.cpp b/src/diagramconnection.cpp
index 545f9bf..1c8d73b 100644
--- a/src/diagramconnection.cpp
+++ b/src/diagramconnection.cpp
@@ -17,27 +17,21 @@
 #include "diagramconnection.h"
 #include "diagramdocument.h"
 #include "diagramobject.h"
+#include "connector.h"
 
 DiagramConnection::DiagramConnection(DiagramItem *parent)
 	: DiagramItem(parent)
 {
+	m_connectors[0] = new Connector(this);
+	m_connectors[1] = new Connector(this);
 	setZValue(1.0);
-	m_objects[0] = 0;
-	m_objects[1] = 0;
 }
 
-void
-DiagramConnection::setSource(DiagramObject *object)
-{
-	m_objects[0] = object;
-	emit endPointChanged();
-}
-
-void
-DiagramConnection::setTarget(DiagramObject *object)
+Connector *
+DiagramConnection::connector(int index) const
 {
-	m_objects[1] = object;
-	emit endPointChanged();
+	Q_ASSERT(index == 0 || index == 1);
+	return m_connectors[index];
 }
 
 void
@@ -56,8 +50,8 @@ DiagramConnection::loadFromXml(QDomElement element, DiagramDocument *document)
 		QString sourceId = readStringElement(connectionElement, "source");
 		QString targetId = readStringElement(connectionElement, "target");
 		if (document) {
-			setSource(qobject_cast<DiagramObject *>(document->itemById(sourceId)));
-			setTarget(qobject_cast<DiagramObject *>(document->itemById(targetId)));
+/*			setSource(qobject_cast<DiagramObject *>(document->itemById(sourceId)));
+			setTarget(qobject_cast<DiagramObject *>(document->itemById(targetId)));*/
 		}
 	}
 }
@@ -68,8 +62,8 @@ DiagramConnection::saveToXml(QDomDocument doc, QDomElement element)
 	DiagramItem::saveToXml(doc, element);
 	QDomElement connectionElement = doc.createElement("connection");
 	element.appendChild(connectionElement);
-	if (m_objects[0] != NULL)
+/*	if (m_objects[0] != NULL)
 		appendStringElement(doc, connectionElement, "source", m_objects[0]->id());
 	if (m_objects[1] != NULL)
-		appendStringElement(doc, connectionElement, "target", m_objects[1]->id());
+		appendStringElement(doc, connectionElement, "target", m_objects[1]->id());*/
 }
diff --git a/src/diagramconnection.h b/src/diagramconnection.h
index 8dcc721..66ad706 100644
--- a/src/diagramconnection.h
+++ b/src/diagramconnection.h
@@ -18,6 +18,7 @@
 #define DIAGRAMCONNECTION_H
 
 #include "diagramitem.h"
+class Connector;
 class DiagramObject;
 
 class DiagramConnection : public DiagramItem
@@ -27,11 +28,13 @@ class DiagramConnection : public DiagramItem
 public:
 	DiagramConnection(DiagramItem *parent = 0);
 
-	DiagramObject *source() const { return m_objects[0]; }
-	DiagramObject *target() const { return m_objects[1]; }
+	enum LineLayout
+	{
+		StraightLineLayout,
+		OrthogonalLineLayout
+	};
 
-	void setSource(DiagramObject *object);
-	void setTarget(DiagramObject *object);
+	Connector *connector(int index) const;
 
 	virtual void updatePositions();
 
@@ -42,7 +45,7 @@ signals:
 	void endPointChanged();
 
 private:
-	DiagramObject *m_objects[2];
+	Connector *m_connectors[2];
 };
 
 #endif
diff --git a/src/diagramdocument.cpp b/src/diagramdocument.cpp
index e5caf13..ea73abe 100644
--- a/src/diagramdocument.cpp
+++ b/src/diagramdocument.cpp
@@ -15,6 +15,7 @@
 // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 #include <cmath>
+#include "hub.h"
 #include "diagramdocument.h"
 #include "diagramobject.h"
 #include "diagramconnection.h"
@@ -140,8 +141,16 @@ DiagramDocument::setMode(Mode mode)
 void
 DiagramDocument::updatePositions(DiagramObject *object)
 {
-	foreach (DiagramConnection *connection, findConnections(object))
+    Connector *connector;
+	foreach (DiagramConnection *connection, findConnections(object)) {
+        connector = connection->connector(0);
+        if (connector->isConnected())
+            connector->hub()->update();
+        connector = connection->connector(1);
+        if (connector->isConnected())
+            connector->hub()->update();
 		connection->updatePositions();
+    }
 }
 
 template <class T> QList<T *>
@@ -243,8 +252,10 @@ DiagramDocument::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
 		if (source && target && source != target) {
 			DatabaseRelationship *relation = new DatabaseRelationship();
 			relation->createId();
-			relation->setSource(source);
-			relation->setTarget(target);
+			relation->connector(0)->setHub(source->hub());
+			relation->connector(1)->setHub(target->hub());
+            source->hub()->update();
+            target->hub()->update();
 			undoStack()->push(new AddItemCommand(this, relation));
 		}
 		delete m_line;
@@ -288,7 +299,7 @@ DiagramDocument::findConnections(DiagramObject *object)
 {
 	QList<DiagramConnection *> result;
 	foreach (DiagramConnection *connection, itemsByType<DiagramConnection>())
-		if (connection->source() == object || connection->target() == object)
+		if (connection->connector(0)->connectedObject() == object || connection->connector(1)->connectedObject() == object)
 			result.append(connection);
 	return result;
 }
diff --git a/src/diagramitem.cpp b/src/diagramitem.cpp
index 5b5133e..3079590 100644
--- a/src/diagramitem.cpp
+++ b/src/diagramitem.cpp
@@ -26,18 +26,6 @@ DiagramItem::DiagramItem(DiagramItem *parent)
 {
 }
 
-void
-DiagramItem::setId(QUuid id)
-{
-	m_id = id;
-}
-
-void
-DiagramItem::createId()
-{
-	m_id = QUuid::createUuid();
-}
-
 DiagramDocument *
 DiagramItem::document() const
 {
diff --git a/src/diagramitem.h b/src/diagramitem.h
index e0ce662..f597a48 100644
--- a/src/diagramitem.h
+++ b/src/diagramitem.h
@@ -20,12 +20,12 @@
 #include <QGraphicsItem>
 #include <QDomDocument>
 #include <QDomElement>
-#include <QUuid>
+#include "identifiableobject.h"
 class QMimeData;
 class DiagramDocument;
 class DiagramItemProperties;
 
-class DiagramItem : public QObject, public QGraphicsItem
+class DiagramItem : public QObject, public QGraphicsItem, public IdentifiableObject
 {
 	Q_OBJECT
 
@@ -37,10 +37,6 @@ public:
 
 	DiagramDocument *document() const;
 
-	QUuid id() const { return m_id; }
-	void setId(QUuid id);
-	void createId();
-
 	DiagramItem(DiagramItem *parent = 0);
 
 	static const char *staticTypeName() { return ""; }
@@ -56,9 +52,6 @@ public:
 
 signals:
 	void propertyChanged(const QString &name, const QVariant &value);
-
-public:
-	QUuid m_id;
 };
 
 #endif
diff --git a/src/diagramobject.cpp b/src/diagramobject.cpp
index e0d6c17..6783455 100644
--- a/src/diagramobject.cpp
+++ b/src/diagramobject.cpp
@@ -17,7 +17,19 @@
 #include "diagramobject.h"
 
 DiagramObject::DiagramObject(DiagramItem *parent)
-	: DiagramItem(parent)
+	: DiagramItem(parent), m_hub(NULL)
 {
 	setZValue(100.0);
 }
+
+Hub *
+DiagramObject::hub() const
+{
+	return m_hub;
+}
+
+void
+DiagramObject::setHub(Hub *hub)
+{
+	m_hub = hub;
+}
diff --git a/src/diagramobject.h b/src/diagramobject.h
index 6650968..96b027c 100644
--- a/src/diagramobject.h
+++ b/src/diagramobject.h
@@ -18,6 +18,8 @@
 #define DIAGRAMOBJECT_H
 
 #include "diagramitem.h"
+class Hub;
+class DiagramConnection;
 
 class DiagramObject : public DiagramItem
 {
@@ -25,6 +27,15 @@ class DiagramObject : public DiagramItem
 
 public:
 	DiagramObject(DiagramItem *parent = 0);
+
+	Hub *hub() const;
+
+protected:
+	void setHub(Hub *hub);
+
+private:
+	Hub *m_hub;
+	//QMap<ConnectionSlot, DiagramConnection*> m_connections;
 };
 
 #endif
diff --git a/src/hub.cpp b/src/hub.cpp
new file mode 100644
index 0000000..aec14a6
--- /dev/null
+++ b/src/hub.cpp
@@ -0,0 +1,52 @@
+// Copyright (C) 2008  Lukas Lalinsky
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+#include "hub.h"
+#include "diagramobject.h"
+
+Hub::Hub(DiagramObject *owner)
+	: m_owner(owner)
+{
+}
+
+DiagramObject *
+Hub::owner() const
+{
+	return m_owner;
+}
+
+void
+Hub::addConnector(Connector *connector)
+{
+	m_connectors.insert(connector);
+}
+
+void
+Hub::removeConnector(Connector *connector)
+{
+	m_connectors.remove(connector);
+}
+
+QSet<Connector *>
+Hub::connectors() const
+{
+	return m_connectors;
+}
+
+void
+Hub::update()
+{
+}
diff --git a/src/hub.h b/src/hub.h
new file mode 100644
index 0000000..83ff2fd
--- /dev/null
+++ b/src/hub.h
@@ -0,0 +1,42 @@
+// Copyright (C) 2008  Lukas Lalinsky
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+#ifndef HUB_H
+#define HUB_H
+
+#include <QSet>
+class Connector;
+class DiagramObject;
+
+class Hub
+{
+public:
+	Hub(DiagramObject *owner);
+	DiagramObject *owner() const;
+
+	void addConnector(Connector *connector);
+	void removeConnector(Connector *connector);
+
+	virtual void update();
+
+	QSet<Connector *> connectors() const;
+
+private:
+	QSet<Connector *> m_connectors;
+	DiagramObject *m_owner;
+};
+
+#endif
diff --git a/src/items/database/column.h b/src/items/database/column.h
index 36e6680..bbf4fff 100644
--- a/src/items/database/column.h
+++ b/src/items/database/column.h
@@ -20,8 +20,9 @@
 #include <QObject>
 #include <QString>
 #include "columnlist.h"
+#include "identifiableobject.h"
 
-class Column : public QObject
+class Column : public QObject, public IdentifiableObject
 {
 	Q_OBJECT
 	Q_PROPERTY(QString name READ name WRITE setName)
diff --git a/src/items/database/databasecommands.cpp b/src/items/database/databasecommands.cpp
index 7156d4a..eae59db 100644
--- a/src/items/database/databasecommands.cpp
+++ b/src/items/database/databasecommands.cpp
@@ -26,8 +26,10 @@
 AddColumnCommand::AddColumnCommand(ColumnList *columnList, Column *column, QUndoCommand *parent)
 	: QUndoCommand(parent), m_columnList(columnList), m_column(column)
 {
-	if (!m_column)
+	if (!m_column) {
 		m_column = new Column();
+		m_column->createId();
+	}
 	m_index = columnList->columnCount();
 }
 
diff --git a/src/items/database/databaserelationship.cpp b/src/items/database/databaserelationship.cpp
index 3be258c..a95ac6e 100644
--- a/src/items/database/databaserelationship.cpp
+++ b/src/items/database/databaserelationship.cpp
@@ -291,8 +291,11 @@ DatabaseRelationship::updateLayout()
 	if (!scene())
 		return;
 
-	DatabaseTable *source = sourceTable();
-	DatabaseTable *target = targetTable();
+    Connector *connector1 = connector(0);
+    Connector *connector2 = connector(1);
+    
+	DatabaseTable *source = childTable();
+	DatabaseTable *target = parentTable();
 	if (!source || !target)
 		return;
 
@@ -339,80 +342,42 @@ DatabaseRelationship::updateLayout()
 		}
 	}
 
-	// Two-segment line
-	if (0 && !haveLine) {
-
-		qreal x1, x2, x3, y1, y2, y3;
-
-		if (rect1.right() < rect2.left()) {
-			x1 = rect1.right();
-			y1 = verticalRange1.center();
-
-			x2 = horizontalRange2.center();
-			y2 = verticalRange1.center();
-
-			if (rect1.bottom() < rect2.top()) {
-				x3 = horizontalRange2.center();
-				y3 = rect2.top();
-			}
-			else {
-				x3 = horizontalRange2.center();
-				y3 = rect2.bottom();
-			}
+	// Orthogonal line
+	if (!haveLine) {
+		QPointF p1 = connector1->pos();
+		QPointF p2 = connector2->pos();
+		qreal a1 = connector1->angle();
+		qreal a2 = connector2->angle();
+
+		QLineF line1 = QLineF::fromPolar(1, a1).translated(p1);
+		QLineF line2 = QLineF::fromPolar(1, a2).translated(p2);
+		QPointF intersection;
+		d->line.clear();
+		d->line << p1;
+		if (line1.intersect(line2, &intersection) != QLineF::NoIntersection) {
+			// 2-segment line
+			d->line << intersection;
 		}
 		else {
-			x1 = rect1.left();
-			y1 = verticalRange1.center();
-
-			x2 = horizontalRange2.center();
-			y2 = verticalRange1.center();
-
-			if (rect1.bottom() < rect2.top()) {
-				x3 = horizontalRange2.center();
-				y3 = rect2.top();
+			if (line1.intersect(line2.normalVector(), &intersection) != QLineF::NoIntersection) {
+				// 3-segment line
+				qreal len = QLineF(p1, intersection).length() * 0.5;
+				d->line << QLineF::fromPolar(len, a1).translated(p1).p2();
+				d->line << QLineF::fromPolar(len, a2).translated(p2).p2();
 			}
 			else {
-				x3 = horizontalRange2.center();
-				y3 = rect2.bottom();
+				qFatal("No line?");
 			}
 		}
-
-		d->line = QPolygonF()
-			<< QPointF(x1, y1)
-			<< QPointF(x2, y2)
-			<< QPointF(x3, y3);
+		d->line << p2;
 		haveLine = true;
 	}
 
 	// Simple center<->center line
 	if (!haveLine) {
-		QPointF p1 = rect1.center();
-		QPointF p2 = rect2.center();
-		QLineF finalLine = QLineF(p1, p2);
-
-		QPolygonF polygon;
-	
-		polygon = rect1;
-		for (int i = 0; i < 4; i++) {
-			QLineF line(polygon[i], polygon[(i+1)%4]);
-			QPointF intersectionPoint;
-			if (finalLine.intersect(line, &intersectionPoint) == QLineF::BoundedIntersection) {
-				finalLine.setP1(intersectionPoint);
-				break;
-			}
-		}
-	
-		polygon = rect2;
-		for (int i = 0; i < 4; i++) {
-			QLineF line(polygon[i], polygon[(i+1)%4]);
-			QPointF intersectionPoint;
-			if (finalLine.intersect(line, &intersectionPoint) == QLineF::BoundedIntersection) {
-				finalLine.setP2(intersectionPoint);
-				break;
-			}
-		}
-
-		d->line = QPolygonF() << finalLine.p1() << finalLine.p2();
+		QPointF p1 = connector1->pos();
+		QPointF p2 = connector2->pos();
+		d->line = QPolygonF() << p1 << p2;
 		haveLine = true;
 	}
 
diff --git a/src/items/database/databaserelationship.h b/src/items/database/databaserelationship.h
index 5a21c98..f8f381e 100644
--- a/src/items/database/databaserelationship.h
+++ b/src/items/database/databaserelationship.h
@@ -22,6 +22,7 @@
 #include <QPainter>
 #include "diagramconnection.h"
 #include "databasetable.h"
+#include "connector.h"
 
 class DatabaseRelationship : public DiagramConnection
 {
@@ -41,11 +42,8 @@ public:
 	QPainterPath shape() const;
 	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
 
-	DatabaseTable *sourceTable() const { return qobject_cast<DatabaseTable *>(source()); }
-	DatabaseTable *targetTable() const { return qobject_cast<DatabaseTable *>(target()); }
-
-	DatabaseTable *childTable() const { return sourceTable(); }
-	DatabaseTable *parentTable() const { return targetTable(); }
+	DatabaseTable *childTable() const { return qobject_cast<DatabaseTable *>(connector(0)->connectedObject()); }
+	DatabaseTable *parentTable() const { return qobject_cast<DatabaseTable *>(connector(1)->connectedObject()); }
 
 	enum { Type = DiagramItem::Relation };
 	virtual int type() const { return Type; }
diff --git a/src/items/database/databasetable.cpp b/src/items/database/databasetable.cpp
index ca3827b..3c6318a 100644
--- a/src/items/database/databasetable.cpp
+++ b/src/items/database/databasetable.cpp
@@ -22,12 +22,14 @@
 #include "diagramdocument.h"
 #include "column.h"
 #include "columnlist.h"
+#include "boxsidehub.h"
 
 DatabaseTable::DatabaseTable(DiagramItem *parent)
 	: DiagramObject(parent)
 {
 	setFlag(ItemIsMovable);
 	setFlag(ItemIsSelectable);
+	setHub(new BoxSideHub(this));
 	m_columnList = new ColumnList(this);
 	connect(m_columnList, SIGNAL(columnInserted(int)), this, SLOT(updateLayout()));
 	connect(m_columnList, SIGNAL(columnRemoved(int)), this, SLOT(updateLayout()));
diff --git a/src/src.pri b/src/src.pri
index 2dcc581..5a96c1f 100644
--- a/src/src.pri
+++ b/src/src.pri
@@ -3,6 +3,9 @@ DEPENDPATH += $$PWD
 RESOURCES = ../dbmodel.qrc
 
 SOURCES = \
+	connector.cpp \
+	hub.cpp \
+	boxsidehub.cpp \
 	main.cpp \
 	mainwindow.cpp \
 	diagramview.cpp \
@@ -12,9 +15,13 @@ SOURCES = \
 	diagramitemfactory.cpp \
 	diagramitemproperties.cpp \
 	diagramobject.cpp \
+	identifiableobject.cpp \
 	commands.cpp
 
 HEADERS = \
+	connector.h \
+	hub.h \
+	boxsidehub.h \
 	mainwindow.h \
 	diagramview.h \
 	diagramdocument.h \
@@ -23,6 +30,7 @@ HEADERS = \
 	diagramitemfactory.h \
 	diagramitemproperties.h \
 	diagramobject.h \
+	identifiableobject.h \
 	commands.h
 
 TRANSLATIONS = \