How to change the color of the rectangle when you click on the button "Color"

Question

I need to make a color selection for a rectangle using QColorDialog. When I click on the color select button and choose a color, the color of the rectangle changes

import sys

from PyQt5.QtCore import Qt, QRectF, QPointF
from PyQt5.QtGui import QBrush, QPainterPath, QPainter, QColor, QPen, QPixmap
from PyQt5.QtWidgets import QGraphicsRectItem, QApplication, QGraphicsView, QGraphicsScene, QGraphicsItem


class GraphicsRectItem(QGraphicsRectItem):

    handleTopLeft = 1
    handleTopMiddle = 2
    handleTopRight = 3
    handleMiddleLeft = 4
    handleMiddleRight = 5
    handleBottomLeft = 6
    handleBottomMiddle = 7
    handleBottomRight = 8

    handleSize = +8.0
    handleSpace = -4.0

    handleCursors = {
        handleTopLeft: Qt.SizeFDiagCursor,
        handleTopMiddle: Qt.SizeVerCursor,
        handleTopRight: Qt.SizeBDiagCursor,
        handleMiddleLeft: Qt.SizeHorCursor,
        handleMiddleRight: Qt.SizeHorCursor,
        handleBottomLeft: Qt.SizeBDiagCursor,
        handleBottomMiddle: Qt.SizeVerCursor,
        handleBottomRight: Qt.SizeFDiagCursor,
    }

    def __init__(self, *args):
        """
        Initialize the shape.
        """
        super().__init__(*args)
        self.handles = {}
        self.handleSelected = None
        self.mousePressPos = None
        self.mousePressRect = None
        self.setAcceptHoverEvents(True)
        self.setFlag(QGraphicsItem.ItemIsMovable, True)
        self.setFlag(QGraphicsItem.ItemIsSelectable, True)
        self.setFlag(QGraphicsItem.ItemSendsGeometryChanges, True)
        self.setFlag(QGraphicsItem.ItemIsFocusable, True)
        self.updateHandlesPos()

    def handleAt(self, point):
        """
        Returns the resize handle below the given point.
        """
        for k, v, in self.handles.items():
            if v.contains(point):
                return k
        return None

    def hoverMoveEvent(self, moveEvent):
        """
        Executed when the mouse moves over the shape (NOT PRESSED).
        """
        if self.isSelected():
            handle = self.handleAt(moveEvent.pos())
            cursor = Qt.ArrowCursor if handle is None else self.handleCursors[handle]
            self.setCursor(cursor)
        super().hoverMoveEvent(moveEvent)

    def hoverLeaveEvent(self, moveEvent):
        """
        Executed when the mouse leaves the shape (NOT PRESSED).
        """
        self.setCursor(Qt.ArrowCursor)
        super().hoverLeaveEvent(moveEvent)

    def mousePressEvent(self, mouseEvent):
        """
        Executed when the mouse is pressed on the item.
        """
        self.handleSelected = self.handleAt(mouseEvent.pos())
        if self.handleSelected:
            self.mousePressPos = mouseEvent.pos()
            self.mousePressRect = self.boundingRect()
        super().mousePressEvent(mouseEvent)

    def mouseMoveEvent(self, mouseEvent):
        """
        Executed when the mouse is being moved over the item while being pressed.
        """
        if self.handleSelected is not None:
            self.interactiveResize(mouseEvent.pos())
        else:
            super().mouseMoveEvent(mouseEvent)

    def mouseReleaseEvent(self, mouseEvent):
        """
        Executed when the mouse is released from the item.
        """
        super().mouseReleaseEvent(mouseEvent)
        self.handleSelected = None
        self.mousePressPos = None
        self.mousePressRect = None
        self.update()

    def boundingRect(self):
        """
        Returns the bounding rect of the shape (including the resize handles).
        """
        o = self.handleSize + self.handleSpace
        return self.rect().adjusted(-o, -o, o, o)

    def updateHandlesPos(self):
        """
        Update current resize handles according to the shape size and position.
        """
        s = self.handleSize
        b = self.boundingRect()
        self.handles[self.handleTopLeft] = QRectF(b.left(), b.top(), s, s)
        self.handles[self.handleTopMiddle] = QRectF(b.center().x() - s / 2, b.top(), s, s)
        self.handles[self.handleTopRight] = QRectF(b.right() - s, b.top(), s, s)
        self.handles[self.handleMiddleLeft] = QRectF(b.left(), b.center().y() - s / 2, s, s)
        self.handles[self.handleMiddleRight] = QRectF(b.right() - s, b.center().y() - s / 2, s, s)
        self.handles[self.handleBottomLeft] = QRectF(b.left(), b.bottom() - s, s, s)
        self.handles[self.handleBottomMiddle] = QRectF(b.center().x() - s / 2, b.bottom() - s, s, s)
        self.handles[self.handleBottomRight] = QRectF(b.right() - s, b.bottom() - s, s, s)

    def interactiveResize(self, mousePos):
        """
        Perform shape interactive resize.
        """
        offset = self.handleSize + self.handleSpace
        boundingRect = self.boundingRect()
        rect = self.rect()
        diff = QPointF(0, 0)

        self.prepareGeometryChange()

        if self.handleSelected == self.handleTopLeft:

            fromX = self.mousePressRect.left()
            fromY = self.mousePressRect.top()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setLeft(toX)
            boundingRect.setTop(toY)
            rect.setLeft(boundingRect.left() + offset)
            rect.setTop(boundingRect.top() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleTopMiddle:

            fromY = self.mousePressRect.top()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setY(toY - fromY)
            boundingRect.setTop(toY)
            rect.setTop(boundingRect.top() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleTopRight:

            fromX = self.mousePressRect.right()
            fromY = self.mousePressRect.top()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setRight(toX)
            boundingRect.setTop(toY)
            rect.setRight(boundingRect.right() - offset)
            rect.setTop(boundingRect.top() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleMiddleLeft:

            fromX = self.mousePressRect.left()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            diff.setX(toX - fromX)
            boundingRect.setLeft(toX)
            rect.setLeft(boundingRect.left() + offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleMiddleRight:
            print("MR")
            fromX = self.mousePressRect.right()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            diff.setX(toX - fromX)
            boundingRect.setRight(toX)
            rect.setRight(boundingRect.right() - offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleBottomLeft:

            fromX = self.mousePressRect.left()
            fromY = self.mousePressRect.bottom()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setLeft(toX)
            boundingRect.setBottom(toY)
            rect.setLeft(boundingRect.left() + offset)
            rect.setBottom(boundingRect.bottom() - offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleBottomMiddle:

            fromY = self.mousePressRect.bottom()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setY(toY - fromY)
            boundingRect.setBottom(toY)
            rect.setBottom(boundingRect.bottom() - offset)
            self.setRect(rect)

        elif self.handleSelected == self.handleBottomRight:

            fromX = self.mousePressRect.right()
            fromY = self.mousePressRect.bottom()
            toX = fromX + mousePos.x() - self.mousePressPos.x()
            toY = fromY + mousePos.y() - self.mousePressPos.y()
            diff.setX(toX - fromX)
            diff.setY(toY - fromY)
            boundingRect.setRight(toX)
            boundingRect.setBottom(toY)
            rect.setRight(boundingRect.right() - offset)
            rect.setBottom(boundingRect.bottom() - offset)
            self.setRect(rect)

        self.updateHandlesPos()

    def shape(self):
        """
        Returns the shape of this item as a QPainterPath in local coordinates.
        """
        path = QPainterPath()
        path.addRect(self.rect())
        if self.isSelected():
            for shape in self.handles.values():
                path.addEllipse(shape)
        return path

    def paint(self, painter, option, widget=None):
        """
        Paint the node in the graphic view.
        """
        painter.setBrush(QBrush(QColor(255, 0, 0, 100)))
        painter.setPen(QPen(QColor(0, 0, 0), 1.0, Qt.SolidLine))
        painter.drawRect(self.rect())

        painter.setRenderHint(QPainter.Antialiasing)
        painter.setBrush(QBrush(QColor(255, 0, 0, 255)))
        painter.setPen(QPen(QColor(0, 0, 0, 255), 1.0, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
        for handle, rect in self.handles.items():
            if self.handleSelected is None or handle == self.handleSelected:
                painter.drawEllipse(rect)


import random


def main():

    app = QApplication(sys.argv)

    grview = QGraphicsView()
    scene = QGraphicsScene(grview)
    scene.setSceneRect(0, 0, 680, 459)
    grview.setScene(scene)
    for _ in range(10):
        item = GraphicsRectItem(0, 0, 300, 150)
        scene.addItem(item)
        item.setPos(QPointF(*random.sample(range(300), 2)))

    grview.fitInView(scene.sceneRect(), Qt.KeepAspectRatio)
    grview.show()
    sys.exit(app.exec_())

I expect that when you click on the "Color" button, you can choose any color for the rectangle.

Answer 1

Instead of doing a custom painting you must use the setBrush method of QGraphicsRectItem. On the other hand I have implemented the context menu so that when you right click and select the option there will be the QColorDialog so you can choose the color

# ...
def __init__(self, *args):
    """
    Initialize the shape.
    """
    super().__init__(*args)
    self.setBrush(QBrush(QColor(255, 0, 0, 100)))
    self.setPen(QPen(QColor(0, 0, 0), 1.0, Qt.SolidLine))
    # ...

def paint(self, painter, option, widget=None):
    option.state &= ~QStyle.State_Selected
    super().paint(painter, option, widget)

    painter.setRenderHint(QPainter.Antialiasing)
    painter.setBrush(QBrush(QColor(255, 0, 0, 255)))
    painter.setPen(QPen(QColor(0, 0, 0, 255), 1.0, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
    for handle, rect in self.handles.items():
        if self.handleSelected is None or handle == self.handleSelected:
            painter.drawEllipse(rect)

def contextMenuEvent(self, event):
    menu = QMenu()
    color_action = menu.addAction("Change color")
    selected_action = menu.exec_(event.screenPos())
    if selected_action == color_action:
        color = QColorDialog.getColor()
        self.setBrush(QBrush(color))
# ...