Hello,
can you give your solution ?
Christophe.
2013/4/14 Tom Brown <nextst...@gmail.com>
> Ah! I found the QGraphicsView.mapToScene() method. This solved my problem.
>
> Thanks!
> Tom
>
>
> On Sat, Apr 13, 2013 at 6:06 PM, Tom Brown <nextst...@gmail.com> wrote:
>
>> I've found that this problem isn't specific to a bezier curve. If I
>> change the curve to a straight line, I observe the same problem. So, I
>> would think that it has something to do with the way I'm setting up the
>> view.
>>
>> Any ideas would be appreciated.
>>
>> Thanks!
>> Tom
>>
>>
>>
>> On Sat, Apr 13, 2013 at 5:15 PM, Tom Brown <nextst...@gmail.com> wrote:
>>
>>> I've created a simple application (see below) that draws a bezier curve.
>>> I want to give the user the ability to select the curve so they can move it
>>> around. However, I'm having trouble selecting the curve in an intuitive
>>> fashion. When I click on the curve, the point I click on is actually far
>>> away from the curve.
>>>
>>> For example, when I click on the left end of the curve, the x-coordinate
>>> of the point where I clicked is about 100 pixels away from the x-coordinate
>>> of the point of the curve I clicked on.
>>>
>>> The code below demonstrates this problem.
>>>
>>> Any ideas why this is happening or what I'm doing wrong?
>>>
>>> Thanks!
>>> Tom
>>>
>>> <code>
>>> from math import sqrt
>>> from sys import argv
>>>
>>> from PyQt4.Qt import QApplication
>>> from PyQt4.QtCore import QPointF, Qt
>>> from PyQt4.QtGui import (
>>> QColor,
>>> QGraphicsItem,
>>> QGraphicsView,
>>> QGraphicsScene,
>>> QPainterPath,
>>> )
>>>
>>>
>>> class View(QGraphicsView):
>>> def __init__(self, parent=None):
>>> super(View, self).__init__(parent)
>>> self.epsilon = 11.0
>>> self.graphics_scene = QGraphicsScene(self)
>>> self.setScene(self.graphics_scene)
>>> self.add_curve()
>>>
>>> def mousePressEvent(self, event):
>>> if event.button() == Qt.LeftButton:
>>> self.select_item_at(event.x(), event.y())
>>>
>>> def select_item_at(self, x, y):
>>> self.unselect_items()
>>> for item in self.items():
>>> if item.contains_point(x, y, self.epsilon):
>>> item.set_selected(True)
>>> item.update()
>>>
>>> def unselect_items(self):
>>> for item in self.items():
>>> item.set_selected(False)
>>> item.update()
>>>
>>> def add_curve(self):
>>> color = QColor(255, 0, 0)
>>> x0 = 600.0
>>> y0 = 400.0
>>> x1 = 800.0
>>> y1 = 500.0
>>> x2 = 1000.0
>>> y2 = 500.0
>>> x3 = 1200.0
>>> y3 = 400.0
>>> control_points = (QPointF(x0, y0), QPointF(x1, y1),
>>> QPointF(x2, y2), QPointF(x3, y3))
>>> curve = Curve(color, control_points)
>>> self.graphics_scene.addItem(curve)
>>>
>>>
>>> class Curve(QGraphicsItem):
>>> def __init__(self, color, control_points, parent=None, scene=None):
>>> super(Curve, self).__init__(parent, scene)
>>> self.selected = False
>>> self.color = color
>>> self.path = QPainterPath()
>>> self.path.moveTo(control_points[0])
>>> self.path.cubicTo(*control_points[1:])
>>>
>>> def set_selected(self, selected):
>>> self.selected = selected
>>>
>>> def contains_point(self, x, y, epsilon):
>>> p = (x, y)
>>> min_distance = float(0x7fffffff)
>>> t = 0.0
>>> while t < 1.0:
>>> point = self.path.pointAtPercent(t)
>>> spline_point = (point.x(), point.y())
>>> print p, spline_point
>>> distance = self.distance(p, spline_point)
>>> if distance < min_distance:
>>> min_distance = distance
>>> t += 0.1
>>> print min_distance, epsilon
>>> return (min_distance <= epsilon)
>>>
>>> def boundingRect(self):
>>> return self.path.boundingRect()
>>>
>>> def paint(self, painter, option, widget):
>>> painter.setPen(self.color)
>>> painter.setBrush(self.color)
>>> painter.strokePath(self.path, painter.pen())
>>>
>>> def distance(self, p0, p1):
>>> a = p1[0] - p0[0]
>>> b = p1[1] - p0[1]
>>> return sqrt(a * a + b * b)
>>>
>>>
>>> if __name__ == '__main__':
>>> app = QApplication(argv)
>>> view = View()
>>> view.setGeometry(100, 100, 1600, 900)
>>> view.setWindowTitle('MainWindow')
>>> view.show()
>>> app.exec_()
>>>
>>> </code>
>>>
>>
>>
>
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