elasticnodes.py

#!/usr/bin/env python


#############################################################################
##
## Copyright (C) 2013 Riverbank Computing Limited.
## Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
## All rights reserved.
##
## This file is part of the examples of PyQt.
##
## $QT_BEGIN_LICENSE:BSD$
## You may use this file under the terms of the BSD license as follows:
##
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## modification, are permitted provided that the following conditions are
## met:
##   * Redistributions of source code must retain the above copyright
##     notice, this list of conditions and the following disclaimer.
##   * Redistributions in binary form must reproduce the above copyright
##     notice, this list of conditions and the following disclaimer in
##     the documentation and/or other materials provided with the
##     distribution.
##   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
##     the names of its contributors may be used to endorse or promote
##     products derived from this software without specific prior written
##     permission.
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## (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
## $QT_END_LICENSE$
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#############################################################################


import math

from PyQt5.QtCore import (qAbs, QLineF, QPointF, qrand, QRectF, QSizeF, qsrand,
        Qt, QTime)
from PyQt5.QtGui import (QBrush, QColor, QLinearGradient, QPainter,
        QPainterPath, QPen, QPolygonF, QRadialGradient)
from PyQt5.QtWidgets import (QApplication, QGraphicsItem, QGraphicsScene,
        QGraphicsView, QStyle)


class Edge(QGraphicsItem):
    Pi = math.pi
    TwoPi = 2.0 * Pi

    Type = QGraphicsItem.UserType + 2

    def __init__(self, sourceNode, destNode):
        super(Edge, self).__init__()

        self.arrowSize = 10.0
        self.sourcePoint = QPointF()
        self.destPoint = QPointF()

        self.setAcceptedMouseButtons(Qt.NoButton)
        self.source = sourceNode
        self.dest = destNode
        self.source.addEdge(self)
        self.dest.addEdge(self)
        self.adjust()

    def type(self):
        return Edge.Type

    def sourceNode(self):
        return self.source

    def setSourceNode(self, node):
        self.source = node
        self.adjust()

    def destNode(self):
        return self.dest

    def setDestNode(self, node):
        self.dest = node
        self.adjust()

    def adjust(self):
        if not self.source or not self.dest:
            return

        line = QLineF(self.mapFromItem(self.source, 0, 0),
                self.mapFromItem(self.dest, 0, 0))
        length = line.length()

        self.prepareGeometryChange()

        if length > 20.0:
            edgeOffset = QPointF((line.dx() * 10) / length,
                    (line.dy() * 10) / length)

            self.sourcePoint = line.p1() + edgeOffset
            self.destPoint = line.p2() - edgeOffset
        else:
            self.sourcePoint = line.p1()
            self.destPoint = line.p1()

    def boundingRect(self):
        if not self.source or not self.dest:
            return QRectF()

        penWidth = 1.0
        extra = (penWidth + self.arrowSize) / 2.0

        return QRectF(self.sourcePoint,
                QSizeF(self.destPoint.x() - self.sourcePoint.x(),
                        self.destPoint.y() - self.sourcePoint.y())).normalized().adjusted(-extra, -extra, extra, extra)

    def paint(self, painter, option, widget):
        if not self.source or not self.dest:
            return

        # Draw the line itself.
        line = QLineF(self.sourcePoint, self.destPoint)

        if line.length() == 0.0:
            return

        painter.setPen(QPen(Qt.black, 1, Qt.SolidLine, Qt.RoundCap,
                Qt.RoundJoin))
        painter.drawLine(line)

        # Draw the arrows if there's enough room.
        angle = math.acos(line.dx() / line.length())
        if line.dy() >= 0:
            angle = Edge.TwoPi - angle

        sourceArrowP1 = self.sourcePoint + QPointF(math.sin(angle + Edge.Pi / 3) * self.arrowSize,
                                                          math.cos(angle + Edge.Pi / 3) * self.arrowSize)
        sourceArrowP2 = self.sourcePoint + QPointF(math.sin(angle + Edge.Pi - Edge.Pi / 3) * self.arrowSize,
                                                          math.cos(angle + Edge.Pi - Edge.Pi / 3) * self.arrowSize);   
        destArrowP1 = self.destPoint + QPointF(math.sin(angle - Edge.Pi / 3) * self.arrowSize,
                                                      math.cos(angle - Edge.Pi / 3) * self.arrowSize)
        destArrowP2 = self.destPoint + QPointF(math.sin(angle - Edge.Pi + Edge.Pi / 3) * self.arrowSize,
                                                      math.cos(angle - Edge.Pi + Edge.Pi / 3) * self.arrowSize)

        painter.setBrush(Qt.black)
        painter.drawPolygon(QPolygonF([line.p1(), sourceArrowP1, sourceArrowP2]))
        painter.drawPolygon(QPolygonF([line.p2(), destArrowP1, destArrowP2]))


class Node(QGraphicsItem):
    Type = QGraphicsItem.UserType + 1

    def __init__(self, graphWidget):
        super(Node, self).__init__()

        self.graph = graphWidget
        self.edgeList = []
        self.newPos = QPointF()

        self.setFlag(QGraphicsItem.ItemIsMovable)
        self.setFlag(QGraphicsItem.ItemSendsGeometryChanges)
        self.setCacheMode(QGraphicsItem.DeviceCoordinateCache)
        self.setZValue(1)

    def type(self):
        return Node.Type

    def addEdge(self, edge):
        self.edgeList.append(edge)
        edge.adjust()

    def edges(self):
        return self.edgeList

    def calculateForces(self):
        if not self.scene() or self.scene().mouseGrabberItem() is self:
            self.newPos = self.pos()
            return
    
        # Sum up all forces pushing this item away.
        xvel = 0.0
        yvel = 0.0
        for item in self.scene().items():
            if not isinstance(item, Node):
                continue

            line = QLineF(self.mapFromItem(item, 0, 0), QPointF(0, 0))
            dx = line.dx()
            dy = line.dy()
            l = 2.0 * (dx * dx + dy * dy)
            if l > 0:
                xvel += (dx * 150.0) / l
                yvel += (dy * 150.0) / l

        # Now subtract all forces pulling items together.
        weight = (len(self.edgeList) + 1) * 10.0
        for edge in self.edgeList:
            if edge.sourceNode() is self:
                pos = self.mapFromItem(edge.destNode(), 0, 0)
            else:
                pos = self.mapFromItem(edge.sourceNode(), 0, 0)
            xvel += pos.x() / weight
            yvel += pos.y() / weight
    
        if qAbs(xvel) < 0.1 and qAbs(yvel) < 0.1:
            xvel = yvel = 0.0

        sceneRect = self.scene().sceneRect()
        self.newPos = self.pos() + QPointF(xvel, yvel)
        self.newPos.setX(min(max(self.newPos.x(), sceneRect.left() + 10), sceneRect.right() - 10))
        self.newPos.setY(min(max(self.newPos.y(), sceneRect.top() + 10), sceneRect.bottom() - 10))

    def advance(self):
        if self.newPos == self.pos():
            return False

        self.setPos(self.newPos)
        return True

    def boundingRect(self):
        adjust = 2.0
        return QRectF(-10 - adjust, -10 - adjust, 23 + adjust, 23 + adjust)

    def shape(self):
        path = QPainterPath()
        path.addEllipse(-10, -10, 20, 20)
        return path

    def paint(self, painter, option, widget):
        painter.setPen(Qt.NoPen)
        painter.setBrush(Qt.darkGray)
        painter.drawEllipse(-7, -7, 20, 20)

        gradient = QRadialGradient(-3, -3, 10)
        if option.state & QStyle.State_Sunken:
            gradient.setCenter(3, 3)
            gradient.setFocalPoint(3, 3)
            gradient.setColorAt(1, QColor(Qt.yellow).lighter(120))
            gradient.setColorAt(0, QColor(Qt.darkYellow).lighter(120))
        else:
            gradient.setColorAt(0, Qt.yellow)
            gradient.setColorAt(1, Qt.darkYellow)

        painter.setBrush(QBrush(gradient))
        painter.setPen(QPen(Qt.black, 0))
        painter.drawEllipse(-10, -10, 20, 20)

    def itemChange(self, change, value):
        if change == QGraphicsItem.ItemPositionHasChanged:
            for edge in self.edgeList:
                edge.adjust()
            self.graph.itemMoved()

        return super(Node, self).itemChange(change, value)

    def mousePressEvent(self, event):
        self.update()
        super(Node, self).mousePressEvent(event)

    def mouseReleaseEvent(self, event):
        self.update()
        super(Node, self).mouseReleaseEvent(event)


class GraphWidget(QGraphicsView):
    def __init__(self):
        super(GraphWidget, self).__init__()

        self.timerId = 0

        scene = QGraphicsScene(self)
        scene.setItemIndexMethod(QGraphicsScene.NoIndex)
        scene.setSceneRect(-200, -200, 400, 400)
        self.setScene(scene)
        self.setCacheMode(QGraphicsView.CacheBackground)
        self.setViewportUpdateMode(QGraphicsView.BoundingRectViewportUpdate)
        self.setRenderHint(QPainter.Antialiasing)
        self.setTransformationAnchor(QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QGraphicsView.AnchorViewCenter)

        node1 = Node(self)
        node2 = Node(self)
        node3 = Node(self)
        node4 = Node(self)
        self.centerNode = Node(self)
        node6 = Node(self)
        node7 = Node(self)
        node8 = Node(self)
        node9 = Node(self)
        scene.addItem(node1)
        scene.addItem(node2)
        scene.addItem(node3)
        scene.addItem(node4)
        scene.addItem(self.centerNode)
        scene.addItem(node6)
        scene.addItem(node7)
        scene.addItem(node8)
        scene.addItem(node9)
        scene.addItem(Edge(node1, node2))
        scene.addItem(Edge(node2, node3))
        scene.addItem(Edge(node2, self.centerNode))
        scene.addItem(Edge(node3, node6))
        scene.addItem(Edge(node4, node1))
        scene.addItem(Edge(node4, self.centerNode))
        scene.addItem(Edge(self.centerNode, node6))
        scene.addItem(Edge(self.centerNode, node8))
        scene.addItem(Edge(node6, node9))
        scene.addItem(Edge(node7, node4))
        scene.addItem(Edge(node8, node7))
        scene.addItem(Edge(node9, node8))

        node1.setPos(-50, -50)
        node2.setPos(0, -50)
        node3.setPos(50, -50)
        node4.setPos(-50, 0)
        self.centerNode.setPos(0, 0)
        node6.setPos(50, 0)
        node7.setPos(-50, 50)
        node8.setPos(0, 50)
        node9.setPos(50, 50)

        self.scale(0.8, 0.8)
        self.setMinimumSize(400, 400)
        self.setWindowTitle("Elastic Nodes")

    def itemMoved(self):
        if not self.timerId:
            self.timerId = self.startTimer(1000 / 25)

    def keyPressEvent(self, event):
        key = event.key()

        if key == Qt.Key_Up:
            self.centerNode.moveBy(0, -20)
        elif key == Qt.Key_Down:
            self.centerNode.moveBy(0, 20)
        elif key == Qt.Key_Left:
            self.centerNode.moveBy(-20, 0)
        elif key == Qt.Key_Right:
            self.centerNode.moveBy(20, 0)
        elif key == Qt.Key_Plus:
            self.scaleView(1.2)
        elif key == Qt.Key_Minus:
            self.scaleView(1 / 1.2)
        elif key == Qt.Key_Space or key == Qt.Key_Enter:
            for item in self.scene().items():
                if isinstance(item, Node):
                    item.setPos(-150 + qrand() % 300, -150 + qrand() % 300)
        else:
            super(GraphWidget, self).keyPressEvent(event)

    def timerEvent(self, event):
        nodes = [item for item in self.scene().items() if isinstance(item, Node)]

        for node in nodes:
            node.calculateForces()

        itemsMoved = False
        for node in nodes:
            if node.advance():
                itemsMoved = True

        if not itemsMoved:
            self.killTimer(self.timerId)
            self.timerId = 0

    def wheelEvent(self, event):
        self.scaleView(math.pow(2.0, -event.angleDelta().y() / 240.0))

    def drawBackground(self, painter, rect):
        # Shadow.
        sceneRect = self.sceneRect()
        rightShadow = QRectF(sceneRect.right(), sceneRect.top() + 5, 5,
                sceneRect.height())
        bottomShadow = QRectF(sceneRect.left() + 5, sceneRect.bottom(),
                sceneRect.width(), 5)
        if rightShadow.intersects(rect) or rightShadow.contains(rect):
	        painter.fillRect(rightShadow, Qt.darkGray)
        if bottomShadow.intersects(rect) or bottomShadow.contains(rect):
	        painter.fillRect(bottomShadow, Qt.darkGray)

        # Fill.
        gradient = QLinearGradient(sceneRect.topLeft(), sceneRect.bottomRight())
        gradient.setColorAt(0, Qt.white)
        gradient.setColorAt(1, Qt.lightGray)
        painter.fillRect(rect.intersected(sceneRect), QBrush(gradient))
        painter.setBrush(Qt.NoBrush)
        painter.drawRect(sceneRect)

        # Text.
        textRect = QRectF(sceneRect.left() + 4, sceneRect.top() + 4,
                sceneRect.width() - 4, sceneRect.height() - 4)
        message = "Click and drag the nodes around, and zoom with the " \
                "mouse wheel or the '+' and '-' keys"

        font = painter.font()
        font.setBold(True)
        font.setPointSize(14)
        painter.setFont(font)
        painter.setPen(Qt.lightGray)
        painter.drawText(textRect.translated(2, 2), message)
        painter.setPen(Qt.black)
        painter.drawText(textRect, message)

    def scaleView(self, scaleFactor):
        factor = self.transform().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width()

        if factor < 0.07 or factor > 100:
            return

        self.scale(scaleFactor, scaleFactor)


if __name__ == '__main__':

    import sys

    app = QApplication(sys.argv)
    qsrand(QTime(0,0,0).secsTo(QTime.currentTime()))

    widget = GraphWidget()
    widget.show()

    sys.exit(app.exec_())