PR #2011 + anti-aliasing enabled leads to line artifacts #2178
Description
Short description
PR #2011 introduced an optimized way to plot thick lines. However, when anti-aliasing is enabled, this
leads to line artifacts.
Code to reproduce
import pyqtgraph as pg
pg.setConfigOptions(antialias=True)
pg.setConfigOption('background', 'w')
pg.setConfigOption('foreground', 'k')
import pyqtgraph.Qt.QtWidgets as QtWidgets
import numpy as np
win = pg.GraphicsLayoutWidget(show=True)
win.resize(800,350)
win.setWindowTitle('pyqtgraph example: #2011 test')
plt1 = win.addPlot(title='With anti-aliasing and alpha = 1')
plt2 = win.addPlot(title='With anti-aliasing and alpha != 1')
x = np.linspace(0, 2*np.pi, 25)
y = np.sin(x)
WIDTH = 4.0
color = (0, 113, 188)
pen = pg.mkPen(color + (255,), width=WIDTH)
pen_alpha = pg.mkPen(color + (254,), width=WIDTH)
plt1.plot(x, y, pen=pen)
plt2.plot(x, y, pen=pen_alpha)
QtWidgets.QApplication.instance().exec_()Expected behavior
Fallback to the old drawing method whenever anti-aliasing is enabled (just as is the case if alpha < 1).
Real behavior
Line artifacts are seen for thicker lines.
Tested environment(s)
- PyQtGraph version: commit Id 8436457 and newer
- Qt Python binding: PySide2 5.15.1 Qt 5.15.1
- Python version: 3.8.10
- NumPy version: 1.19.2
- Operating system: XUbuntu 20.04.2 LTS
- Installation method: pip