Analysis of applicable scenarios for PyQt6/PySide6’s QPropertyAnimation class

1. Overview

QGraphicsViewandQGraphicsSceneIt is the core class of the Qt Graphics View Framework for building high-performance, interactive 2D graphical interfaces.
Core division of labor：

QGraphicsScene: Manage graph items in the scene (QGraphicsItem), handles events and coordinate systems.
QGraphicsView: As the viewport for observing the scene, it provides view transformation functions such as zoom, translation, and rotation.

Applicable scenarios：

Complex drawings (such as CAD tools)
Game Development (2D Scene)
Data visualization (charts, flow charts)
Interactive graphical interface (components that can be dragged and edited)

2. Core components and relationships

Component level

QGraphicsView (view)
  └── QGraphicsScene (Scene)
      └── QGraphicsItem (Graphics Items：rectangle、oval、text、Custom items, etc.)

Coordinate system difference

Scene coordinates: The global coordinate system of the scene (or origin is in the center of the scene or in the custom position).
View coordinates: The coordinate system of the view window (original point is in the upper left corner).
Item coordinates: The local coordinate system of each graphic item itself.

3. Basic usage steps

Create scenes and views

from  import QGraphicsView, QGraphicsScene, QApplication
from  import Qt
scene = QGraphicsScene()  # Create a sceneview = QGraphicsView(scene)  # Create a view and bind the scene()  # Anti-aliasing(800, 600)
()

Add graphics items to the scene

# Add rectangle (position, size, color)rect = (0, 0, 100, 50, , )
# Add texttext = ("Hello Graphics", QFont("Arial", 12))
(50, 50)
# Add an ellipseellipse = (200, 100, 80, 60, )

4. Core functions and practical cases

Interactive graphics items (drag, rotate)

class MovableRect(QGraphicsRectItem):
    def __init__(self, x, y, w, h):
        super().__init__(x, y, w, h)
        ()  # Allow drag and drop        ()  # Allow to select        ()
# Add movable rectangle to the scenemovable_rect = MovableRect(300, 200, 80, 40)
(movable_rect)

View operations (zoom and pan)

# Mouse wheel zoomdef wheelEvent(self, event):
    factor = 1.2 if ().y() &gt; 0 else 0.8
    (factor, factor)
# Right-click drag and pan()  # Set drag mode

Custom graphics items (draw arrows)

class ArrowItem(QGraphicsItem):
    def boundingRect(self):
        return QRectF(-10, -5, 20, 10)  # Define item boundaries    def paint(self, painter, option, widget):
        (QPen(, 2))
        (0, 0, 10, 0)  # Arrow body        (10, 0, 5, -5)  # Arrow tip        (10, 0, 5, 5)
arrow = ArrowItem()
(400, 300)
(arrow)

Combining animation and graphics items

# Use QPropertyAnimation to move graphics itemsfrom  import QPropertyAnimation
anim = QPropertyAnimation(arrow, b"pos")
(2000)
(QPointF(400, 300))
(QPointF(500, 400))
()
()

V. Advanced features

Collision detection

# Detect the collision between rectangles and other itemscolliding_items = ()
for item in colliding_items:
    ()  # Highlight collision item

Combination items (QGraphicsItemGroup)

group = QGraphicsItemGroup()
(rect)
(text)
(45)  # Overall rotation 45 degrees(group)

Scene event processing

class CustomScene(QGraphicsScene):
    def mousePressEvent(self, event):
        if () == :
            print(f"Scene Click Location：{()}")
        super().mousePressEvent(event)

6. Things to note

Performance optimization

Avoid placing too many items (more than thousands) in the scene.
useorsetCacheModeOptimize rendering.

Coordinate conversion

usemapToScene()andmapFromScene()Convert coordinates between views, scenes, and items.

# Convert view coordinates (100, 200) to scene coordinatesscene_pos = (100, 200)

Memory management

Called when deleting graphic itemsremoveItem(), avoid memory leaks.

(rect)
del rect  # Explicitly delete objects

7. Comprehensive case: Simple drawing tool

class DrawingScene(QGraphicsScene):
    def __init__(self):
        super().__init__()
        self.current_item = None
    def mousePressEvent(self, event):
        if () == :
            self.current_item = QGraphicsEllipseItem()
            self.current_item.setRect(().x(), 
                                     ().y(), 
                                     0, 0)
            (self.current_item)
    def mouseMoveEvent(self, event):
        if self.current_item:
            start_pos = ()
            current_pos = ()
            self.current_item.setRect(
                start_pos.x(), start_pos.y(),
                current_pos.x() - start_pos.x(),
                current_pos.y() - start_pos.y()
            )
    def mouseReleaseEvent(self, event):
        self.current_item = None
#User Exampleapp = QApplication([])
scene = DrawingScene()
view = QGraphicsView(scene)
()
()

8. Summary

QGraphicsView and QGraphicsScene provide powerful support for complex graphics applications, enabling highly customized interactive interfaces by combining graphics items, processing events and optimizing rendering. During development, focus should be on coordinate systems, performance management and user interaction logic.

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