Details
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Bug
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Resolution: Unresolved
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P2: Important
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None
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5.15.2
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None
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Qt 5.15.2, Windows 10, PySide2, Python 3.10
(Also tested with PyQt5)
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Windows
Description
QPainter.fillPath() results in incorrect pictures when using in QGraphicsItem.paint() with a QOpenGLWidget set as viewport to the corresponding QGraphicsView.
See the attached screenshot, generated using the mwe below.
The green filled area painted using QPainter.fillPath(p) differs from the red line painted using QPainter.drawPath(p), where the same p is used for both.
Note, that if no QOpenGLWidget is used as viewport (remove the two corresponding lines in the mwe), the bug disappears.
Also the distortion depends on the value ranges of the x values in the mwe. For example, using a small offset x0 = 0 lets the bug also disappear.
MWE
The bug can be reproduced with the following mwe, using python 3.10 and PySide2.
import numpy as np from PySide2 import QtCore, QtGui, QtWidgets class PlotItem(QtWidgets.QGraphicsItem): def __init__(self, parent, x, y): super().__init__(parent) self.x = x self.y = y def boundingRect(self): return QtCore.QRectF(min(x),min(y), max(x)-min(x), max(y)-min(y)) def paint(self, painter, option, widget): poly = QtGui.QPolygonF([QtCore.QPointF(x,y) for x,y in zip(self.x,self.y)]) path = QtGui.QPainterPath() path.addPolygon(poly) # This works correct (only as a reference here) pen = QtGui.QPen(QtGui.QColor("#ff0000")) pen.setCosmetic(True) painter.setPen(pen) painter.drawPath(path) # This doesn't work painter.fillPath(path, QtGui.QBrush(QtGui.QColor("#00ff00"))) x0 = 100000.0 # Large error # x0 = 20000 # Small error # x0 = 0 # Works x_range = 0.1 num_samples = 10 x = np.linspace(x0, x0+x_range, num_samples, endpoint=False) y = -np.linspace(0,1,num_samples, endpoint=False) x = x[:len(y)] y[::2] = 0.0 y = np.concatenate(([0.0], y, [0.0])) x = np.concatenate(([x[0]], x, [x[-1]])) # [print([x_,y_]) for x_,y_ in zip(x,y)] app = QtWidgets.QApplication() scene = QtWidgets.QGraphicsScene() view = QtWidgets.QGraphicsView(scene) view.resize(300,200) v = QtWidgets.QOpenGLWidget() view.setViewport(v) view.show() scene.setBackgroundBrush(QtGui.QBrush(QtGui.QColor("black"))) plot_item = PlotItem(None,x,y) scene.addItem(plot_item) view.fitInView(plot_item) app.exec_()
