examples/widgets/graphicsview/elasticnodes¶
(You can also check this code in the repository)
# Copyright (C) 2013 Riverbank Computing Limited.
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations
import sys
import weakref
import math
from PySide6.QtCore import (QLineF, QPointF, QRandomGenerator, QRectF, QSizeF,
Qt, qAbs)
from PySide6.QtGui import (QColor, QBrush, QLinearGradient, QPainter, QPainterPath, QPen,
QPolygonF, QRadialGradient)
from PySide6.QtWidgets import (QApplication, QGraphicsItem, QGraphicsScene,
QGraphicsView, QStyle)
def random(boundary):
return QRandomGenerator.global_().bounded(boundary)
class Edge(QGraphicsItem):
def __init__(self, sourceNode, destNode):
super().__init__()
self._arrow_size = 10.0
self._source_point = QPointF()
self._dest_point = QPointF()
self.setAcceptedMouseButtons(Qt.NoButton)
self.source = weakref.ref(sourceNode)
self.dest = weakref.ref(destNode)
self.source().add_edge(self)
self.dest().add_edge(self)
self.adjust()
def item_type(self):
return QGraphicsItem.UserType + 2
def source_node(self):
return self.source()
def set_source_node(self, node):
self.source = weakref.ref(node)
self.adjust()
def dest_node(self):
return self.dest()
def set_dest_node(self, node):
self.dest = weakref.ref(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()
if length == 0.0:
return
edge_offset = QPointF((line.dx() * 10) / length, (line.dy() * 10) / length)
self.prepareGeometryChange()
self._source_point = line.p1() + edge_offset
self._dest_point = line.p2() - edge_offset
def boundingRect(self):
if not self.source() or not self.dest():
return QRectF()
pen_width = 1
extra = (pen_width + self._arrow_size) / 2.0
width = self._dest_point.x() - self._source_point.x()
height = self._dest_point.y() - self._source_point.y()
rect = QRectF(self._source_point, QSizeF(width, height))
return rect.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._source_point, self._dest_point)
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 = 2 * math.pi - angle
arrow_head1 = QPointF(math.sin(angle + math.pi / 3) * self._arrow_size,
math.cos(angle + math.pi / 3) * self._arrow_size)
source_arrow_p1 = self._source_point + arrow_head1
arrow_head2 = QPointF(math.sin(angle + math.pi - math.pi / 3) * self._arrow_size,
math.cos(angle + math.pi - math.pi / 3) * self._arrow_size)
source_arrow_p2 = self._source_point + arrow_head2
arrow_head1 = QPointF(math.sin(angle - math.pi / 3) * self._arrow_size,
math.cos(angle - math.pi / 3) * self._arrow_size)
dest_arrow_p1 = self._dest_point + arrow_head1
arrow_head2 = QPointF(math.sin(angle - math.pi + math.pi / 3) * self._arrow_size,
math.cos(angle - math.pi + math.pi / 3) * self._arrow_size)
dest_arrow_p2 = self._dest_point + arrow_head2
painter.setBrush(Qt.black)
painter.drawPolygon(QPolygonF([line.p1(), source_arrow_p1, source_arrow_p2]))
painter.drawPolygon(QPolygonF([line.p2(), dest_arrow_p1, dest_arrow_p2]))
class Node(QGraphicsItem):
def __init__(self, graphWidget):
super().__init__()
self.graph = weakref.ref(graphWidget)
self._edge_list = []
self._new_pos = QPointF()
self.setFlag(QGraphicsItem.ItemIsMovable)
self.setFlag(QGraphicsItem.ItemSendsGeometryChanges)
self.setCacheMode(QGraphicsItem.DeviceCoordinateCache)
self.setZValue(-1)
def item_type(self):
return QGraphicsItem.UserType + 1
def add_edge(self, edge):
self._edge_list.append(weakref.ref(edge))
edge.adjust()
def edges(self):
return self._edge_list
def calculate_forces(self):
if not self.scene() or self.scene().mouseGrabberItem() is self:
self._new_pos = 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) # noqa: E741
if l > 0:
xvel += (dx * 150.0) / l
yvel += (dy * 150.0) / l
# Now subtract all forces pulling items together.
weight = (len(self._edge_list) + 1) * 10.0
for edge in self._edge_list:
if edge().source_node() is self:
pos = self.mapFromItem(edge().dest_node(), 0, 0)
else:
pos = self.mapFromItem(edge().source_node(), 0, 0)
xvel += pos.x() / weight
yvel += pos.y() / weight
if qAbs(xvel) < 0.1 and qAbs(yvel) < 0.1:
xvel = yvel = 0.0
scene_rect = self.scene().sceneRect()
self._new_pos = self.pos() + QPointF(xvel, yvel)
self._new_pos.setX(min(max(self._new_pos.x(), scene_rect.left() + 10),
scene_rect.right() - 10))
self._new_pos.setY(min(max(self._new_pos.y(), scene_rect.top() + 10),
scene_rect.bottom() - 10))
def advance(self):
if self._new_pos == self.pos():
return False
self.setPos(self._new_pos)
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.ItemPositionChange:
for edge in self._edge_list:
edge().adjust()
self.graph().item_moved()
return QGraphicsItem.itemChange(self, change, value)
def mousePressEvent(self, event):
self.update()
QGraphicsItem.mousePressEvent(self, event)
def mouseReleaseEvent(self, event):
self.update()
QGraphicsItem.mouseReleaseEvent(self, event)
class GraphWidget(QGraphicsView):
def __init__(self):
super().__init__()
self._timer_id = 0
scene = QGraphicsScene(self)
scene.setItemIndexMethod(QGraphicsScene.NoIndex)
scene.setSceneRect(-200, -200, 400, 400)
self.setScene(scene)
self.setCacheMode(QGraphicsView.CacheBackground)
self.setRenderHint(QPainter.RenderHint.Antialiasing)
self.setTransformationAnchor(QGraphicsView.AnchorUnderMouse)
self.setResizeAnchor(QGraphicsView.AnchorViewCenter)
node1 = Node(self)
node2 = Node(self)
node3 = Node(self)
node4 = Node(self)
self._center_node = 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._center_node)
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._center_node))
scene.addItem(Edge(node3, node6))
scene.addItem(Edge(node4, node1))
scene.addItem(Edge(node4, self._center_node))
scene.addItem(Edge(self._center_node, node6))
scene.addItem(Edge(self._center_node, 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._center_node.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(self.tr("Elastic Nodes"))
def item_moved(self):
if not self._timer_id:
self._timer_id = self.startTimer(1000 / 25)
def keyPressEvent(self, event):
key = event.key()
if key == Qt.Key_Up:
self._center_node.moveBy(0, -20)
elif key == Qt.Key_Down:
self._center_node.moveBy(0, 20)
elif key == Qt.Key_Left:
self._center_node.moveBy(-20, 0)
elif key == Qt.Key_Right:
self._center_node.moveBy(20, 0)
elif key == Qt.Key_Plus:
self.scale_view(1.2)
elif key == Qt.Key_Minus:
self.scale_view(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 + random(300), -150 + random(300))
else:
QGraphicsView.keyPressEvent(self, event)
def timerEvent(self, event):
nodes = [item for item in self.scene().items() if isinstance(item, Node)]
for node in nodes:
node.calculate_forces()
items_moved = False
for node in nodes:
if node.advance():
items_moved = True
if not items_moved:
self.killTimer(self._timer_id)
self._timer_id = 0
def wheelEvent(self, event):
delta = event.angleDelta().y()
self.scale_view(math.pow(2.0, -delta / 240.0))
def draw_background(self, painter, rect):
# Shadow.
scene_rect = self.sceneRect()
right_shadow = QRectF(scene_rect.right(), scene_rect.top() + 5,
5, scene_rect.height())
bottom_shadow = QRectF(scene_rect.left() + 5, scene_rect.bottom(),
scene_rect.width(), 5)
if right_shadow.intersects(rect) or right_shadow.contains(rect):
painter.fillRect(right_shadow, Qt.darkGray)
if bottom_shadow.intersects(rect) or bottom_shadow.contains(rect):
painter.fillRect(bottom_shadow, Qt.darkGray)
# Fill.
gradient = QLinearGradient(scene_rect.topLeft(), scene_rect.bottomRight())
gradient.setColorAt(0, Qt.white)
gradient.setColorAt(1, Qt.lightGray)
painter.fillRect(rect.intersected(scene_rect), QBrush(gradient))
painter.setBrush(Qt.NoBrush)
painter.drawRect(scene_rect)
# Text.
text_rect = QRectF(scene_rect.left() + 4, scene_rect.top() + 4,
scene_rect.width() - 4, scene_rect.height() - 4)
message = self.tr("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(text_rect.translated(2, 2), message)
painter.setPen(Qt.black)
painter.drawText(text_rect, message)
def scale_view(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__":
app = QApplication(sys.argv)
widget = GraphWidget()
widget.show()
sys.exit(app.exec())