防止 QPainter 点超出 window 范围

Question

我有一个 PyQt 应用程序，我必须在其中实现 drap n drop 通过 QPainter 点的功能。我的问题是我什至可以将这些点拖到 window 范围之外，例如我可以将点拖到标题栏或任务栏并将其留在那里，一旦留在那里，我就不能再将它们拖回我的 Mainwindow.

请提供解决方案，这样我就永远无法将它们拖到那里。

代码：

import sys
import numpy as np

from PyQt4 import QtCore, QtGui


class Canvas(QtGui.QWidget):

    DELTA = 100 #for the minimum distance        

    def __init__(self, parent=None):
        super(Canvas, self).__init__(parent)
        self.draggin_idx = -1        
        self.points = np.array([[x[0],x[1]] for x in [[100,200], [200,200], [100,400], [200,400]]], dtype=np.float)  
        self.id = None 

        self.points_dict = {}

        for i, x in enumerate(self.points):
            point=(int(x[0]),int(x[1]))
            self.points_dict[i] = point

    def paintEvent(self, e):
        qp = QtGui.QPainter()
        qp.begin(self)
        self.drawPoints(qp)
        self.drawLines(qp)
        qp.end()

    def drawPoints(self, qp):
        # qp.setPen(QtCore.Qt.red)
        pen = QtGui.QPen()
        pen.setWidth(10)
        pen.setColor(QtGui.QColor('red'))
        qp.setPen(pen)
        for x,y in self.points:
            qp.drawPoint(x,y)        

    def drawLines(self, qp):
        # pen.setWidth(5)
        # pen.setColor(QtGui.QColor('red'))
        qp.setPen(QtCore.Qt.red)
        qp.drawLine(self.points_dict[0][0], self.points_dict[0][1], self.points_dict[1][0], self.points_dict[1][1])
        qp.drawLine(self.points_dict[1][0], self.points_dict[1][1], self.points_dict[3][0], self.points_dict[3][1])
        qp.drawLine(self.points_dict[3][0], self.points_dict[3][1], self.points_dict[2][0], self.points_dict[2][1])
        qp.drawLine(self.points_dict[2][0], self.points_dict[2][1], self.points_dict[0][0], self.points_dict[0][1])

    def _get_point(self, evt):
        return np.array([evt.pos().x(),evt.pos().y()])

    #get the click coordinates
    def mousePressEvent(self, evt):
        if evt.button() == QtCore.Qt.LeftButton and self.draggin_idx == -1:
            point = self._get_point(evt)
            int_point = (int(point[0]), int(point[1]))
            min_dist = ((int_point[0]-self.points_dict[0][0])**2 + (int_point[1]-self.points_dict[0][1])**2)**0.5
            
            for i, x in enumerate(list(self.points_dict.values())):
                distance = ((int_point[0]-x[0])**2 + (int_point[1]-x[1])**2)**0.5
                if min_dist >= distance:
                    min_dist = distance
                    self.id = i
                    
            #dist will hold the square distance from the click to the points
            dist = self.points - point
            dist = dist[:,0]**2 + dist[:,1]**2
            dist[dist>self.DELTA] = np.inf #obviate the distances above DELTA
            if dist.min() < np.inf:
                self.draggin_idx = dist.argmin()        

    def mouseMoveEvent(self, evt):
        if self.draggin_idx != -1:
            point = self._get_point(evt)
            self.points[self.draggin_idx] = point
            self.update()

    def mouseReleaseEvent(self, evt):
        if evt.button() == QtCore.Qt.LeftButton and self.draggin_idx != -1:
            point = self._get_point(evt)
            int_point = (int(point[0]), int(point[1]))
            self.points_dict[self.id] = int_point
            self.points[self.draggin_idx] = point
            self.draggin_idx = -1
            self.update()


if __name__ == "__main__":
    app = QtGui.QApplication([])
    win = Canvas()
    win.showMaximized()
    sys.exit(app.exec_())

Answer 1

这与绘画无关（它显然不能“走出去”），而是与您获取坐标的方式有关。

只需确保该点位于小部件的边距内：

    def _get_point(self, evt):
        pos = evt.pos()
        if pos.x() < 0:
            pos.setX(0)
        elif pos.x() > self.width():
            pos.setX(self.width())
        if pos.y() < 0:
            pos.setY(0)
        elif pos.y() > self.height():
            pos.setY(self.height())
        return np.array([pos.x(), pos.y()])

防止 QPainter 点超出 window 范围

Prevent QPainter point from going outside the window scope

python

pyqt

pyqt4

qpainter

python-3.x