examples/widgets/graphicsview/diagramscene#

(You can also check this code in the repository)

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<!DOCTYPE RCC><RCC version="1.0">
<qresource>
    <file>images/pointer.png</file>
    <file>images/linepointer.png</file>
    <file>images/textpointer.png</file>
    <file>images/bold.png</file>
    <file>images/italic.png</file>
    <file>images/underline.png</file>
    <file>images/floodfill.png</file>
    <file>images/bringtofront.png</file>
    <file>images/delete.png</file>
    <file>images/sendtoback.png</file>
    <file>images/linecolor.png</file>
    <file>images/background1.png</file>
    <file>images/background2.png</file>
    <file>images/background3.png</file>
    <file>images/background4.png</file>
</qresource>
</RCC>
# Copyright (C) 2013 Riverbank Computing Limited.
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import math
import sys

from PySide6.QtCore import (QLineF, QPointF, QRect, QRectF, QSize, QSizeF, Qt,
                            Signal, Slot)
from PySide6.QtGui import (QAction, QBrush, QColor, QFont, QIcon, QIntValidator,
                           QPainter, QPainterPath, QPen, QPixmap, QPolygonF)
from PySide6.QtWidgets import (QAbstractButton, QApplication, QButtonGroup,
                               QComboBox, QFontComboBox, QGraphicsItem, QGraphicsLineItem,
                               QGraphicsPolygonItem, QGraphicsTextItem,
                               QGraphicsScene, QGraphicsView, QGridLayout,
                               QHBoxLayout, QLabel, QMainWindow, QMenu,
                               QMessageBox, QSizePolicy, QToolBox, QToolButton,
                               QWidget)

import diagramscene_rc


class Arrow(QGraphicsLineItem):
    def __init__(self, startItem, endItem, parent=None, scene=None):
        super().__init__(parent, scene)

        self._arrow_head = QPolygonF()

        self._my_start_item = startItem
        self._my_end_item = endItem
        self.setFlag(QGraphicsItem.ItemIsSelectable, True)
        self._my_color = Qt.black
        self.setPen(QPen(self._my_color, 2, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))

    def set_color(self, color):
        self._my_color = color

    def start_item(self):
        return self._my_start_item

    def end_item(self):
        return self._my_end_item

    def boundingRect(self):
        extra = (self.pen().width() + 20) / 2.0
        p1 = self.line().p1()
        p2 = self.line().p2()
        rect = QRectF(p1, QSizeF(p2.x() - p1.x(), p2.y() - p1.y()))
        return rect.normalized().adjusted(-extra, -extra, extra, extra)

    def shape(self):
        path = super(Arrow, self).shape()
        path.addPolygon(self._arrow_head)
        return path

    def update_position(self):
        start = self.mapFromItem(self._my_start_item, 0, 0)
        end = self.mapFromItem(self._my_end_item, 0, 0)
        self.setLine(QLineF(start, end))

    def paint(self, painter, option, widget=None):
        if (self._my_start_item.collidesWithItem(self._my_end_item)):
            return

        my_start_item = self._my_start_item
        my_end_item = self._my_end_item
        my_color = self._my_color
        my_pen = self.pen()
        my_pen.setColor(self._my_color)
        arrow_size = 20.0
        painter.setPen(my_pen)
        painter.setBrush(self._my_color)

        center_line = QLineF(my_start_item.pos(), my_end_item.pos())
        end_polygon = my_end_item.polygon()
        p1 = end_polygon.at(0) + my_end_item.pos()

        intersect_point = QPointF()
        for i in end_polygon:
            p2 = i + my_end_item.pos()
            poly_line = QLineF(p1, p2)
            intersectType, intersect_point = poly_line.intersects(center_line)
            if intersectType == QLineF.BoundedIntersection:
                break
            p1 = p2

        self.setLine(QLineF(intersect_point, my_start_item.pos()))
        line = self.line()

        angle = math.acos(line.dx() / line.length())
        if line.dy() >= 0:
            angle = (math.pi * 2.0) - angle

        arrow_head1 = QPointF(math.sin(angle + math.pi / 3.0) * arrow_size,
                              math.cos(angle + math.pi / 3) * arrow_size)
        arrow_p1 = line.p1() + arrow_head1
        arrow_head2 = QPointF(math.sin(angle + math.pi - math.pi / 3.0) * arrow_size,
                              math.cos(angle + math.pi - math.pi / 3.0) * arrow_size)
        arrow_p2 = line.p1() + arrow_head2

        self._arrow_head.clear()
        for point in [line.p1(), arrow_p1, arrow_p2]:
            self._arrow_head.append(point)

        painter.drawLine(line)
        painter.drawPolygon(self._arrow_head)
        if self.isSelected():
            painter.setPen(QPen(my_color, 1, Qt.DashLine))
            my_line = QLineF(line)
            my_line.translate(0, 4.0)
            painter.drawLine(my_line)
            my_line.translate(0, -8.0)
            painter.drawLine(my_line)


class DiagramTextItem(QGraphicsTextItem):
    lost_focus = Signal(QGraphicsTextItem)

    selected_change = Signal(QGraphicsItem)

    def __init__(self, parent=None, scene=None):
        super().__init__(parent, scene)

        self.setFlag(QGraphicsItem.ItemIsMovable)
        self.setFlag(QGraphicsItem.ItemIsSelectable)

    def itemChange(self, change, value):
        if change == QGraphicsItem.ItemSelectedChange:
            self.selected_change.emit(self)
        return value

    def focusOutEvent(self, event):
        self.setTextInteractionFlags(Qt.NoTextInteraction)
        self.lost_focus.emit(self)
        super(DiagramTextItem, self).focusOutEvent(event)

    def mouseDoubleClickEvent(self, event):
        if self.textInteractionFlags() == Qt.NoTextInteraction:
            self.setTextInteractionFlags(Qt.TextEditorInteraction)
        super(DiagramTextItem, self).mouseDoubleClickEvent(event)


class DiagramItem(QGraphicsPolygonItem):
    Step, Conditional, StartEnd, Io = range(4)

    def __init__(self, diagram_type, contextMenu, parent=None, scene=None):
        super().__init__(parent, scene)

        self.arrows = []

        self.diagram_type = diagram_type
        self._my_context_menu = contextMenu

        path = QPainterPath()
        if self.diagram_type == self.StartEnd:
            path.moveTo(200, 50)
            path.arcTo(150, 0, 50, 50, 0, 90)
            path.arcTo(50, 0, 50, 50, 90, 90)
            path.arcTo(50, 50, 50, 50, 180, 90)
            path.arcTo(150, 50, 50, 50, 270, 90)
            path.lineTo(200, 25)
            self._my_polygon = path.toFillPolygon()
        elif self.diagram_type == self.Conditional:
            self._my_polygon = QPolygonF([
                QPointF(-100, 0), QPointF(0, 100),
                QPointF(100, 0), QPointF(0, -100),
                QPointF(-100, 0)])
        elif self.diagram_type == self.Step:
            self._my_polygon = QPolygonF([
                QPointF(-100, -100), QPointF(100, -100),
                QPointF(100, 100), QPointF(-100, 100),
                QPointF(-100, -100)])
        else:
            self._my_polygon = QPolygonF([
                QPointF(-120, -80), QPointF(-70, 80),
                QPointF(120, 80), QPointF(70, -80),
                QPointF(-120, -80)])

        self.setPolygon(self._my_polygon)
        self.setFlag(QGraphicsItem.ItemIsMovable, True)
        self.setFlag(QGraphicsItem.ItemIsSelectable, True)

    def remove_arrow(self, arrow):
        try:
            self.arrows.remove(arrow)
        except ValueError:
            pass

    def remove_arrows(self):
        for arrow in self.arrows[:]:
            arrow.start_item().remove_arrow(arrow)
            arrow.end_item().remove_arrow(arrow)
            self.scene().removeItem(arrow)

    def add_arrow(self, arrow):
        self.arrows.append(arrow)

    def image(self):
        pixmap = QPixmap(250, 250)
        pixmap.fill(Qt.transparent)
        with QPainter(pixmap) as painter:
            painter.setPen(QPen(Qt.black, 8))
            painter.translate(125, 125)
            painter.drawPolyline(self._my_polygon)
        return pixmap

    def contextMenuEvent(self, event):
        self.scene().clearSelection()
        self.setSelected(True)
        self._my_context_menu.exec(event.screenPos())

    def itemChange(self, change, value):
        if change == QGraphicsItem.ItemPositionChange:
            for arrow in self.arrows:
                arrow.updatePosition()

        return value


class DiagramScene(QGraphicsScene):
    InsertItem, InsertLine, InsertText, MoveItem = range(4)

    item_inserted = Signal(DiagramItem)

    text_inserted = Signal(QGraphicsTextItem)

    item_selected = Signal(QGraphicsItem)

    def __init__(self, itemMenu, parent=None):
        super().__init__(parent)

        self._my_item_menu = itemMenu
        self._my_mode = self.MoveItem
        self._my_item_type = DiagramItem.Step
        self.line = None
        self._text_item = None
        self._my_item_color = Qt.white
        self._my_text_color = Qt.black
        self._my_line_color = Qt.black
        self._my_font = QFont()

    def set_line_color(self, color):
        self._my_line_color = color
        if self.is_item_change(Arrow):
            item = self.selectedItems()[0]
            item.set_color(self._my_line_color)
            self.update()

    def set_text_color(self, color):
        self._my_text_color = color
        if self.is_item_change(DiagramTextItem):
            item = self.selectedItems()[0]
            item.setDefaultTextColor(self._my_text_color)

    def set_item_color(self, color):
        self._my_item_color = color
        if self.is_item_change(DiagramItem):
            item = self.selectedItems()[0]
            item.setBrush(self._my_item_color)

    def set_font(self, font):
        self._my_font = font
        if self.is_item_change(DiagramTextItem):
            item = self.selectedItems()[0]
            item.setFont(self._my_font)

    def set_mode(self, mode):
        self._my_mode = mode

    def set_item_type(self, type):
        self._my_item_type = type

    def editor_lost_focus(self, item):
        cursor = item.textCursor()
        cursor.clearSelection()
        item.setTextCursor(cursor)

        if not item.toPlainText():
            self.removeItem(item)
            item.deleteLater()

    def mousePressEvent(self, mouseEvent):
        if (mouseEvent.button() != Qt.LeftButton):
            return

        if self._my_mode == self.InsertItem:
            item = DiagramItem(self._my_item_type, self._my_item_menu)
            item.setBrush(self._my_item_color)
            self.addItem(item)
            item.setPos(mouseEvent.scenePos())
            self.item_inserted.emit(item)
        elif self._my_mode == self.InsertLine:
            self.line = QGraphicsLineItem(QLineF(mouseEvent.scenePos(), mouseEvent.scenePos()))
            self.line.setPen(QPen(self._my_line_color, 2))
            self.addItem(self.line)
        elif self._my_mode == self.InsertText:
            text_item = DiagramTextItem()
            text_item.setFont(self._my_font)
            text_item.setTextInteractionFlags(Qt.TextEditorInteraction)
            text_item.setZValue(1000.0)
            text_item.lost_focus.connect(self.editor_lost_focus)
            text_item.selected_change.connect(self.item_selected)
            self.addItem(text_item)
            text_item.setDefaultTextColor(self._my_text_color)
            text_item.setPos(mouseEvent.scenePos())
            self.text_inserted.emit(text_item)

        super(DiagramScene, self).mousePressEvent(mouseEvent)

    def mouseMoveEvent(self, mouseEvent):
        if self._my_mode == self.InsertLine and self.line:
            new_line = QLineF(self.line.line().p1(), mouseEvent.scenePos())
            self.line.setLine(new_line)
        elif self._my_mode == self.MoveItem:
            super(DiagramScene, self).mouseMoveEvent(mouseEvent)

    def mouseReleaseEvent(self, mouseEvent):
        if self.line and self._my_mode == self.InsertLine:
            start_items = self.items(self.line.line().p1())
            if len(start_items) and start_items[0] == self.line:
                start_items.pop(0)
            end_items = self.items(self.line.line().p2())
            if len(end_items) and end_items[0] == self.line:
                end_items.pop(0)

            self.removeItem(self.line)
            self.line = None

            if (len(start_items) and len(end_items) and
                    isinstance(start_items[0], DiagramItem) and
                    isinstance(end_items[0], DiagramItem) and
                    start_items[0] != end_items[0]):
                start_item = start_items[0]
                end_item = end_items[0]
                arrow = Arrow(start_item, end_item)
                arrow.set_color(self._my_line_color)
                start_item.add_arrow(arrow)
                end_item.add_arrow(arrow)
                arrow.setZValue(-1000.0)
                self.addItem(arrow)
                arrow.update_position()

        self.line = None
        super(DiagramScene, self).mouseReleaseEvent(mouseEvent)

    def is_item_change(self, type):
        for item in self.selectedItems():
            if isinstance(item, type):
                return True
        return False


class MainWindow(QMainWindow):
    insert_text_button = 10

    def __init__(self):
        super().__init__()

        self.create_actions()
        self.create_menus()
        self.create_tool_box()

        self.scene = DiagramScene(self._item_menu)
        self.scene.setSceneRect(QRectF(0, 0, 5000, 5000))
        self.scene.item_inserted.connect(self.item_inserted)
        self.scene.text_inserted.connect(self.text_inserted)
        self.scene.item_selected.connect(self.item_selected)

        self.create_toolbars()

        layout = QHBoxLayout()
        layout.addWidget(self._tool_box)
        self.view = QGraphicsView(self.scene)
        layout.addWidget(self.view)

        self.widget = QWidget()
        self.widget.setLayout(layout)

        self.setCentralWidget(self.widget)
        self.setWindowTitle("Diagramscene")

    @Slot(QAbstractButton)
    def background_button_group_clicked(self, button):
        buttons = self._background_button_group.buttons()
        for myButton in buttons:
            if myButton != button:
                button.setChecked(False)

        text = button.text()
        if text == "Blue Grid":
            self.scene.setBackgroundBrush(QBrush(QPixmap(':/images/background1.png')))
        elif text == "White Grid":
            self.scene.setBackgroundBrush(QBrush(QPixmap(':/images/background2.png')))
        elif text == "Gray Grid":
            self.scene.setBackgroundBrush(QBrush(QPixmap(':/images/background3.png')))
        else:
            self.scene.setBackgroundBrush(QBrush(QPixmap(':/images/background4.png')))

        self.scene.update()
        self.view.update()

    @Slot(int)
    def button_group_clicked(self, idx):
        buttons = self._button_group.buttons()
        for button in buttons:
            if self._button_group.button(idx) != button:
                button.setChecked(False)

        if idx == self.insert_text_button:
            self.scene.set_mode(DiagramScene.InsertText)
        else:
            self.scene.set_item_type(idx)
            self.scene.set_mode(DiagramScene.InsertItem)

    @Slot()
    def delete_item(self):
        for item in self.scene.selectedItems():
            if isinstance(item, DiagramItem):
                item.remove_arrows()
            self.scene.removeItem(item)

    @Slot(int)
    def pointer_group_clicked(self, i):
        self.scene.set_mode(self._pointer_type_group.checkedId())

    @Slot()
    def bring_to_front(self):
        if not self.scene.selectedItems():
            return

        selected_item = self.scene.selectedItems()[0]
        overlap_items = selected_item.collidingItems()

        z_value = 0
        for item in overlap_items:
            if (item.zValue() >= z_value and isinstance(item, DiagramItem)):
                z_value = item.zValue() + 0.1
        selected_item.setZValue(z_value)

    @Slot()
    def send_to_back(self):
        if not self.scene.selectedItems():
            return

        selected_item = self.scene.selectedItems()[0]
        overlap_items = selected_item.collidingItems()

        z_value = 0
        for item in overlap_items:
            if (item.zValue() <= z_value and isinstance(item, DiagramItem)):
                z_value = item.zValue() - 0.1
        selected_item.setZValue(z_value)

    @Slot(QGraphicsPolygonItem)
    def item_inserted(self, item):
        self._pointer_type_group.button(DiagramScene.MoveItem).setChecked(True)
        self.scene.set_mode(self._pointer_type_group.checkedId())
        self._button_group.button(item.diagram_type).setChecked(False)

    @Slot(QGraphicsTextItem)
    def text_inserted(self, item):
        self._button_group.button(self.insert_text_button).setChecked(False)
        self.scene.set_mode(self._pointer_type_group.checkedId())

    @Slot(QFont)
    def current_font_changed(self, font):
        self.handle_font_change()

    @Slot(int)
    def font_size_changed(self, font):
        self.handle_font_change()

    @Slot(str)
    def scene_scale_changed(self, scale):
        new_scale = int(scale[:-1]) / 100.0
        old_matrix = self.view.transform()
        self.view.resetTransform()
        self.view.translate(old_matrix.dx(), old_matrix.dy())
        self.view.scale(new_scale, new_scale)

    @Slot()
    def text_color_changed(self):
        self._text_action = self.sender()
        self._font_color_tool_button.setIcon(self.create_color_tool_button_icon(
            ':/images/textpointer.png', QColor(self._text_action.data())))
        self.text_button_triggered()

    @Slot()
    def item_color_changed(self):
        self._fill_action = self.sender()
        self._fill_color_tool_button.setIcon(self.create_color_tool_button_icon(
            ':/images/floodfill.png', QColor(self._fill_action.data())))
        self.fill_button_triggered()

    @Slot()
    def line_color_changed(self):
        self._line_action = self.sender()
        self._line_color_tool_button.setIcon(self.create_color_tool_button_icon(
            ':/images/linecolor.png', QColor(self._line_action.data())))
        self.line_button_triggered()

    @Slot()
    def text_button_triggered(self):
        self.scene.set_text_color(QColor(self._text_action.data()))

    @Slot()
    def fill_button_triggered(self):
        self.scene.set_item_color(QColor(self._fill_action.data()))

    @Slot()
    def line_button_triggered(self):
        self.scene.set_line_color(QColor(self._line_action.data()))

    @Slot()
    def handle_font_change(self):
        font = self._font_combo.currentFont()
        font.setPointSize(int(self._font_size_combo.currentText()))
        if self._bold_action.isChecked():
            font.setWeight(QFont.Bold)
        else:
            font.setWeight(QFont.Normal)
        font.setItalic(self._italic_action.isChecked())
        font.setUnderline(self._underline_action.isChecked())

        self.scene.set_font(font)

    @Slot(QGraphicsItem)
    def item_selected(self, item):
        font = item.font()
        self._font_combo.setCurrentFont(font)
        self._font_size_combo.setEditText(str(font.pointSize()))
        self._bold_action.setChecked(font.weight() == QFont.Bold)
        self._italic_action.setChecked(font.italic())
        self._underline_action.setChecked(font.underline())

    @Slot()
    def about(self):
        QMessageBox.about(self, "About Diagram Scene",
                          "The <b>Diagram Scene</b> example shows use of the graphics framework.")

    def create_tool_box(self):
        self._button_group = QButtonGroup()
        self._button_group.setExclusive(False)
        self._button_group.idClicked.connect(self.button_group_clicked)

        layout = QGridLayout()
        layout.addWidget(self.create_cell_widget("Conditional", DiagramItem.Conditional), 0, 0)
        layout.addWidget(self.create_cell_widget("Process", DiagramItem.Step), 0, 1)
        layout.addWidget(self.create_cell_widget("Input/Output", DiagramItem.Io), 1, 0)

        text_button = QToolButton()
        text_button.setCheckable(True)
        self._button_group.addButton(text_button, self.insert_text_button)
        text_button.setIcon(QIcon(QPixmap(':/images/textpointer.png')
                            .scaled(30, 30)))
        text_button.setIconSize(QSize(50, 50))

        text_layout = QGridLayout()
        text_layout.addWidget(text_button, 0, 0, Qt.AlignHCenter)
        text_layout.addWidget(QLabel("Text"), 1, 0, Qt.AlignCenter)
        text_widget = QWidget()
        text_widget.setLayout(text_layout)
        layout.addWidget(text_widget, 1, 1)

        layout.setRowStretch(3, 10)
        layout.setColumnStretch(2, 10)

        item_widget = QWidget()
        item_widget.setLayout(layout)

        self._background_button_group = QButtonGroup()
        self._background_button_group.buttonClicked.connect(self.background_button_group_clicked)

        background_layout = QGridLayout()
        background_layout.addWidget(
            self.create_background_cell_widget("Blue Grid", ':/images/background1.png'), 0, 0)
        background_layout.addWidget(
            self.create_background_cell_widget("White Grid", ':/images/background2.png'), 0, 1)
        background_layout.addWidget(
            self.create_background_cell_widget("Gray Grid", ':/images/background3.png'), 1, 0)
        background_layout.addWidget(
            self.create_background_cell_widget("No Grid", ':/images/background4.png'), 1, 1)

        background_layout.setRowStretch(2, 10)
        background_layout.setColumnStretch(2, 10)

        background_widget = QWidget()
        background_widget.setLayout(background_layout)

        self._tool_box = QToolBox()
        self._tool_box.setSizePolicy(QSizePolicy(QSizePolicy.Maximum, QSizePolicy.Ignored))
        self._tool_box.setMinimumWidth(item_widget.sizeHint().width())
        self._tool_box.addItem(item_widget, "Basic Flowchart Shapes")
        self._tool_box.addItem(background_widget, "Backgrounds")

    def create_actions(self):
        self._to_front_action = QAction(
            QIcon(':/images/bringtofront.png'), "Bring to &Front",
            self, shortcut="Ctrl+F", statusTip="Bring item to front",
            triggered=self.bring_to_front)

        self._send_back_action = QAction(
            QIcon(':/images/sendtoback.png'), "Send to &Back", self,
            shortcut="Ctrl+B", statusTip="Send item to back",
            triggered=self.send_to_back)

        self._delete_action = QAction(QIcon(':/images/delete.png'),
                                      "&Delete", self, shortcut="Delete",
                                      statusTip="Delete item from diagram",
                                      triggered=self.delete_item)

        self._exit_action = QAction("E&xit", self, shortcut="Ctrl+X",
                                    statusTip="Quit Scenediagram example", triggered=self.close)

        self._bold_action = QAction(QIcon(':/images/bold.png'),
                                    "Bold", self, checkable=True, shortcut="Ctrl+B",
                                    triggered=self.handle_font_change)

        self._italic_action = QAction(QIcon(':/images/italic.png'),
                                      "Italic", self, checkable=True, shortcut="Ctrl+I",
                                      triggered=self.handle_font_change)

        self._underline_action = QAction(
            QIcon(':/images/underline.png'), "Underline", self,
            checkable=True, shortcut="Ctrl+U",
            triggered=self.handle_font_change)

        self._about_action = QAction("A&bout", self, shortcut="Ctrl+B", triggered=self.about)

    def create_menus(self):
        self._file_menu = self.menuBar().addMenu("&File")
        self._file_menu.addAction(self._exit_action)

        self._item_menu = self.menuBar().addMenu("&Item")
        self._item_menu.addAction(self._delete_action)
        self._item_menu.addSeparator()
        self._item_menu.addAction(self._to_front_action)
        self._item_menu.addAction(self._send_back_action)

        self._about_menu = self.menuBar().addMenu("&Help")
        self._about_menu.addAction(self._about_action)

    def create_toolbars(self):
        self._edit_tool_bar = self.addToolBar("Edit")
        self._edit_tool_bar.addAction(self._delete_action)
        self._edit_tool_bar.addAction(self._to_front_action)
        self._edit_tool_bar.addAction(self._send_back_action)

        self._font_combo = QFontComboBox()
        self._font_combo.currentFontChanged.connect(self.current_font_changed)

        self._font_size_combo = QComboBox()
        self._font_size_combo.setEditable(True)
        for i in range(8, 30, 2):
            self._font_size_combo.addItem(str(i))
        validator = QIntValidator(2, 64, self)
        self._font_size_combo.setValidator(validator)
        self._font_size_combo.currentIndexChanged.connect(self.font_size_changed)

        self._font_color_tool_button = QToolButton()
        self._font_color_tool_button.setPopupMode(QToolButton.MenuButtonPopup)
        self._font_color_tool_button.setMenu(
            self.create_color_menu(self.text_color_changed, Qt.black))
        self._text_action = self._font_color_tool_button.menu().defaultAction()
        self._font_color_tool_button.setIcon(
            self.create_color_tool_button_icon(':/images/textpointer.png', Qt.black))
        self._font_color_tool_button.setAutoFillBackground(True)
        self._font_color_tool_button.clicked.connect(self.text_button_triggered)

        self._fill_color_tool_button = QToolButton()
        self._fill_color_tool_button.setPopupMode(QToolButton.MenuButtonPopup)
        self._fill_color_tool_button.setMenu(
            self.create_color_menu(self.item_color_changed, Qt.white))
        self._fill_action = self._fill_color_tool_button.menu().defaultAction()
        self._fill_color_tool_button.setIcon(
            self.create_color_tool_button_icon(':/images/floodfill.png', Qt.white))
        self._fill_color_tool_button.clicked.connect(self.fill_button_triggered)

        self._line_color_tool_button = QToolButton()
        self._line_color_tool_button.setPopupMode(QToolButton.MenuButtonPopup)
        self._line_color_tool_button.setMenu(
            self.create_color_menu(self.line_color_changed, Qt.black))
        self._line_action = self._line_color_tool_button.menu().defaultAction()
        self._line_color_tool_button.setIcon(
            self.create_color_tool_button_icon(':/images/linecolor.png', Qt.black))
        self._line_color_tool_button.clicked.connect(self.line_button_triggered)

        self._text_tool_bar = self.addToolBar("Font")
        self._text_tool_bar.addWidget(self._font_combo)
        self._text_tool_bar.addWidget(self._font_size_combo)
        self._text_tool_bar.addAction(self._bold_action)
        self._text_tool_bar.addAction(self._italic_action)
        self._text_tool_bar.addAction(self._underline_action)

        self._color_tool_bar = self.addToolBar("Color")
        self._color_tool_bar.addWidget(self._font_color_tool_button)
        self._color_tool_bar.addWidget(self._fill_color_tool_button)
        self._color_tool_bar.addWidget(self._line_color_tool_button)

        pointer_button = QToolButton()
        pointer_button.setCheckable(True)
        pointer_button.setChecked(True)
        pointer_button.setIcon(QIcon(':/images/pointer.png'))
        line_pointer_button = QToolButton()
        line_pointer_button.setCheckable(True)
        line_pointer_button.setIcon(QIcon(':/images/linepointer.png'))

        self._pointer_type_group = QButtonGroup()
        self._pointer_type_group.addButton(pointer_button, DiagramScene.MoveItem)
        self._pointer_type_group.addButton(line_pointer_button, DiagramScene.InsertLine)
        self._pointer_type_group.idClicked.connect(self.pointer_group_clicked)

        self._scene_scale_combo = QComboBox()
        self._scene_scale_combo.addItems(["50%", "75%", "100%", "125%", "150%"])
        self._scene_scale_combo.setCurrentIndex(2)
        self._scene_scale_combo.currentTextChanged.connect(self.scene_scale_changed)

        self._pointer_toolbar = self.addToolBar("Pointer type")
        self._pointer_toolbar.addWidget(pointer_button)
        self._pointer_toolbar.addWidget(line_pointer_button)
        self._pointer_toolbar.addWidget(self._scene_scale_combo)

    def create_background_cell_widget(self, text, image):
        button = QToolButton()
        button.setText(text)
        button.setIcon(QIcon(image))
        button.setIconSize(QSize(50, 50))
        button.setCheckable(True)
        self._background_button_group.addButton(button)

        layout = QGridLayout()
        layout.addWidget(button, 0, 0, Qt.AlignHCenter)
        layout.addWidget(QLabel(text), 1, 0, Qt.AlignCenter)

        widget = QWidget()
        widget.setLayout(layout)

        return widget

    def create_cell_widget(self, text, diagram_type):
        item = DiagramItem(diagram_type, self._item_menu)
        icon = QIcon(item.image())

        button = QToolButton()
        button.setIcon(icon)
        button.setIconSize(QSize(50, 50))
        button.setCheckable(True)
        self._button_group.addButton(button, diagram_type)

        layout = QGridLayout()
        layout.addWidget(button, 0, 0, Qt.AlignHCenter)
        layout.addWidget(QLabel(text), 1, 0, Qt.AlignCenter)

        widget = QWidget()
        widget.setLayout(layout)

        return widget

    def create_color_menu(self, slot, defaultColor):
        colors = [Qt.black, Qt.white, Qt.red, Qt.blue, Qt.yellow]
        names = ["black", "white", "red", "blue", "yellow"]

        color_menu = QMenu(self)
        for color, name in zip(colors, names):
            action = QAction(self.create_color_icon(color), name, self, triggered=slot)
            action.setData(QColor(color))
            color_menu.addAction(action)
            if color == defaultColor:
                color_menu.setDefaultAction(action)
        return color_menu

    def create_color_tool_button_icon(self, imageFile, color):
        pixmap = QPixmap(50, 80)
        pixmap.fill(Qt.transparent)

        with QPainter(pixmap) as painter:
            image = QPixmap(imageFile)
            target = QRect(0, 0, 50, 60)
            source = QRect(0, 0, 42, 42)
            painter.fillRect(QRect(0, 60, 50, 80), color)
            painter.drawPixmap(target, image, source)

        return QIcon(pixmap)

    def create_color_icon(self, color):
        pixmap = QPixmap(20, 20)

        with QPainter(pixmap) as painter:
            painter.setPen(Qt.NoPen)
            painter.fillRect(QRect(0, 0, 20, 20), color)

        return QIcon(pixmap)


if __name__ == '__main__':
    app = QApplication(sys.argv)

    main_window = MainWindow()
    main_window.setGeometry(100, 100, 800, 500)
    main_window.show()

    sys.exit(app.exec())