Move Rectangle
-------------------



.. code-block:: python
    :caption: scripts/PYQT4/01_key_pressed/02_move_rectangle/main.py:

    import sys
    from PyQt5.QtWidgets import QApplication, QMainWindow, QGraphicsView, QGraphicsScene
    from PyQt5.QtCore import Qt, QRectF
    from PyQt5.QtGui import QBrush, QPen

    class RectangleMover(QMainWindow):
        def __init__(self):
            super(RectangleMover, self).__init__()

            self.init_ui()

        def init_ui(self):
            self.setWindowTitle('Move Rectangle with ASWD')

            self.setGeometry(100, 100, 800, 600)

            self.view = QGraphicsView(self)
            self.scene = QGraphicsScene(self)
            self.view.setScene(self.scene)

            self.rectangle = self.scene.addRect(QRectF(0, 0, 50, 50), QPen(), QBrush(Qt.blue))
            self.view.setSceneRect(0, 0, 800, 600)

        def keyPressEvent(self, event):
            if event.key() == Qt.Key_A:  # Move left
                self.rectangle.setPos(self.rectangle.x() - 10, self.rectangle.y())
            elif event.key() == Qt.Key_D:  # Move right
                self.rectangle.setPos(self.rectangle.x() + 10, self.rectangle.y())
            elif event.key() == Qt.Key_W:  # Move up
                self.rectangle.setPos(self.rectangle.x(), self.rectangle.y() - 10)
            elif event.key() == Qt.Key_S:  # Move down
                self.rectangle.setPos(self.rectangle.x(), self.rectangle.y() + 10)

    if __name__ == '__main__':
        app = QApplication(sys.argv)
        window = RectangleMover()
        window.show()
        sys.exit(app.exec_())


This example moves a rectangle up, down, left, or right when the user presses the A, S, W, or D key, respectively.

- ``RectangleMover`` class draws a blue rectangle on ``QGraphicsView`` and moves the rectangle based on user keyboard input.
  
- ``keyPressEvent`` detects keyboard events and moves the rectangle in the corresponding direction.

1. ``QGraphicsView`` is a widget that visualizes 2D graphic items and allows interaction with users.

2. ``QGraphicsScene`` acts as a container storing 2D graphic items, essentially serving as the 'canvas' for these items.

3. The ``setScene()`` method connects the ``QGraphicsScene`` to the ``QGraphicsView``.

4. ``self.scene.addRect(...)``:
   - ``self.scene`` is a ``QGraphicsScene`` object. It acts as a container holding graphic items. To visually display these graphic items, you need ``QGraphicsView``.
   - ``addRect`` is a method of ``QGraphicsScene``, which adds a rectangle graphic item and returns a reference to that item.

5. ``QRectF(0, 0, 50, 50)``:
   - ``QRectF`` is a PyQt class representing a rectangle. In this case, it depicts a rectangle with the top-left corner at (0, 0) and a width and height of 50 units.

6. ``QPen()``:
   - The ``QPen`` class defines the style of the line. The default ``QPen`` is used here, so the rectangle's border will be drawn in the default style.

7. ``QBrush(Qt.blue)``:
   - The ``QBrush`` class defines the style and color to fill a shape. As it's set to ``Qt.blue``, the inside of the rectangle will be filled with blue.