Bug 962 – Incorrect rectangle of active area for interactive selection and move for QGraphicsRectItem

PySide Bugzilla Closed for New Bugs

PySide is now a Qt Add-on and uses the Qt Project's JIRA Bug Tracker instead of this Bugzilla instance. This Bugzilla is left for reference purposes.

Bug 962 - Incorrect rectangle of active area for interactive selection and move for QGraphicsRectItem

Summary:

Incorrect rectangle of active area for interactive selection and move for QGr...

Status:	CLOSED INVALID

Product:	PySide
Classification:	Unclassified
Component:	QtGui
Version:	1.0.5
Platform:	PC MS Windows XP/Vista/7

Importance:	P3 normal
Assigned To:	Hugo Parente Lima

URL:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2011-08-07 18:34 EEST by esp.home
Modified:	2011-10-08 12:07 EEST (History)
CC List:	8 users (show)

See Also:

Attachments
Test python script for show bug (630 bytes, text/plain) 2011-08-07 18:34 EEST, esp.home	Details
Test python script for show bug (580 bytes, text/plain) 2011-08-07 19:01 EEST, esp.home	Details
C++ version, works exactly like Python version on 64 bits systems (664 bytes, text/x-c++src) 2011-08-17 20:40 EEST, Hugo Parente Lima	Details
Show Obsolete (1) Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.

Description esp.home 2011-08-07 18:34:05 EEST

Created attachment 390 [details]
Test python script for show bug

If you set flags "QGraphicsItem.ItemIsSelectable" or
"QGraphicsItem.ItemIsMovable" for QGraphicsRectItem, rectangle of active area
will be a incorrect. TopLeft point of active rect will be a begin in item rect
TopLeft - 1.

For example:
...
item_rect = QGraphicsRectItem()
item_rect.setRect(10, 10, 100, 100)
item_rect.setFlag(QGraphicsItem.ItemIsSelectable, True)

scene.addItem(item_rect)
...

Rect of active area for item selection will be: [ x=9, y=9, w=101, h=101 ] in
scene coordinates.
At the same time, methods boundingRect() and shape() return the correct values.

In PyQt4 this bug is not exist.

Comment 1 esp.home 2011-08-07 19:01:51 EEST

Created attachment 391 [details]
Test python script for show bug

Comment 2 Hugo Parente Lima 2011-08-17 01:16:22 EEST

It behaves exactly the same here with PyQt/py3k and PySide.

Would you write some code that asserts on fail to show de bug?

Comment 3 esp.home 2011-08-17 08:57:19 EEST

(In reply to comment #2)
> It behaves exactly the same here with PyQt/py3k and PySide.

I decided to check the behavior on the Linux x64 platform and the following
configuration:
Python: 2.7.1+ (r271:86832, Apr 11 2011, 18:13:53) x64
PyQt4: 4.8.3-2
PySide: 1.0.1

Behavior between PySide and PyQt4 is equal and incorrectly.

At the same time on Windows platform and the following configuration:
Python: 2.7 x86
PyQt4: 4.8.1
PySide: 1.0.5

PyQt4 working correctly, but incorrectly PySide.

I also want to check this behavior on the Qt C++, and write a test code.


PS:
I would not pay any attention to it, but this behavior is actually a hindrance. 
I can not properly manage graphical items on the scene, because of their active
areas overlap each other.

Comment 4 Hugo Parente Lima 2011-08-17 20:24:38 EEST

QGraphicsView uses floating point coordinates, so I guess your bug is
reproducible on C++ as well due to the fact that it's caused by rounding
problem when converting numbers from int to float/double.

I'll write your example in C++ to check my theory.

Comment 5 Hugo Parente Lima 2011-08-17 20:40:23 EEST

Created attachment 403 [details]
C++ version, works exactly like Python version on 64 bits systems

The same behavior occur on C++, so it's really a Qt problem, probably caused by
floating point vs integers.

Comment 6 renato filho 2011-08-23 00:37:18 EEST

Release PySide 1.0.6

Comment 7 esp.home 2011-10-08 12:07:23 EEST

I found where the problem is.

Problem in Qt source-file qgraphicsscene.cpp in method itemsAtPosition.

/*!
    Returns all items for the screen position in \a event.
*/
QList<QGraphicsItem *> QGraphicsScenePrivate::itemsAtPosition(const QPoint
&/*screenPos*/,
                                                              const QPointF
&scenePos,
                                                              QWidget *widget)
const
{
    Q_Q(const QGraphicsScene);
    QGraphicsView *view = widget ? qobject_cast<QGraphicsView
*>(widget->parentWidget()) : 0;
    if (!view)
        return q->items(scenePos, Qt::IntersectsItemShape, Qt::DescendingOrder,
QTransform());

    const QRectF pointRect(scenePos, QSizeF(1, 1));
    if (!view->isTransformed())
        return q->items(pointRect, Qt::IntersectsItemShape,
Qt::DescendingOrder);

    const QTransform viewTransform = view->viewportTransform();
    return q->items(pointRect, Qt::IntersectsItemShape,
                    Qt::DescendingOrder, viewTransform);
}


Line:
const QRectF pointRect(scenePos, QSizeF(1, 1));

Always checked for intersection with the rectangle 1x1. If position point left
and above on <= 1, function "items" return items.

This is bad.