How to resize a item QGraphicsView?

Pedro_Monteiro

Hello, I made an application using the Qt Designer and PyQt4, I'm using QGraphicsView to display an image with a rectangle on it, I can move the rectangle over the image, but when I move it I can pass the image boundaries and I wanted to limit the rectangle to the image boundary, how could I do that? And another question, how could I change the size of the rectangle using the mouse?

Down a code I'm using for testing, it gets QGraphicsView I did in Designer:

# -*- coding: utf-8 -*-

from PyQt4.QtCore import *
from PyQt4.QtGui import *
import sys
from screen import *

class Main(QWidget, Ui_Form):
	def __init__(self, parent=None):
		super(Main, self).__init__(parent)
		self.setupUi(self)

		self.scene = QGraphicsScene()
		self.cena.setScene(self.scene)
		self.scene.addPixmap(QPixmap("01.png"))

		pen = QPen(Qt.darkMagenta)
		pen.setWidth(4)

		rectangle = self.scence.addRect(5,5,300,150, pen)
		rectangle.setFlag(QGraphicsItem.ItemIsMovable)

	def showEvent(self, event):
		self.cena.fitInView(self.scene.sceneRect(), Qt.IgnoreAspectRatio)

app = QApplication(sys.argv)
window = Main()
window.show()

sys.exit(app.exec_())

The answer can be in C++ or Python.
Thanks.

raven-worx

i will give you an (rough) overview what has to be done:

MOVING

subclass QGraphicsRectItem (add the rect-item as a child of the pixmap item)
on itself call setFlags(QGraphicsItem::ItemSendsGeometryChanges)
override itemChange() and listen to QGraphicsItem::ItemPositionChange and check the value if it is in the parent-item's rect/shape. If not return the adapted value

RESIZING

override the paint event handler of the created custom rect item and paint 4 small rects in each corner of the rect
overrride mousePressEvent() handler and check if the mouse was clicked on a handle, if so save the handle direction in a local variable
overrride mouseMoveEvent() handler and check the variable for the direction, calculate the diff-distance between the last position and the current move-position. Add the diff to the current rect of the item. Also make sure the (like you also have done it for MOVING) that the rect stays inside the parent-item's rect
overrride hoverMoveEvent() handler in case you want to change the cursor when the cursor is over one of the handles

Pedro_Monteiro

@raven-worx I already solved about moving, but the resizing looks hard to do, is there some example, even in C++?