[FIXED] pyqtgraph: Add Items from seperate ViewBox to Legend

Issue

I am basically using the code from this example: https://github.com/pyqtgraph/pyqtgraph/blob/develop/examples/MultiplePlotAxes.py but I added a legend to it using pw.addLegend(). My problem is that the legend only shows the items from axis 1, how would I get it to show the data from all axes?

This is what I get:

Every line that isn't shown in the legend is linked to one of the axes on the right.

Solution

When You are adding viewBox into main plot scene, You are bypassing legend adding mechanism. That's why only line p1.plot([1, 2, 4, 8, 16, 32], name='White plot') adds legend. Therefor You have to add legend manually. It's not a big deal, since we have all the objects in hand.

When adding legend, it returns legend object which You can use to add additional curves.

Here is modified code of MultiplePlotAxes.py script adding legend for all curves:

# -*- coding: utf-8 -*-
"""
Demonstrates a way to put multiple axes around a single plot. 
(This will eventually become a built-in feature of PlotItem)
"""

import pyqtgraph as pg
from pyqtgraph.Qt import QtCore, QtGui

pg.mkQApp()

pw = pg.PlotWidget()

# Add legend item
legend = pw.addLegend()

pw.show()
pw.setWindowTitle('pyqtgraph example: MultiplePlotAxes')
p1 = pw.plotItem
p1.setLabels(left='axis 1')

## create a new ViewBox, link the right axis to its coordinate system
p2 = pg.ViewBox()
p1.showAxis('right')
a = p1.scene().addItem(p2)
p1.getAxis('right').linkToView(p2)
p2.setXLink(p1)
p1.getAxis('right').setLabel('axis2', color='#0000ff')

## create third ViewBox. 
## this time we need to create a new axis as well.
p3 = pg.ViewBox()
ax3 = pg.AxisItem('right')
p1.layout.addItem(ax3, 2, 3)
p1.scene().addItem(p3)
ax3.linkToView(p3)
p3.setXLink(p1)
ax3.setZValue(-10000)
ax3.setLabel('axis 3', color='#ff0000')


## Handle view resizing 
def updateViews():
    ## view has resized; update auxiliary views to match
    global p1, p2, p3
    p2.setGeometry(p1.vb.sceneBoundingRect())
    p3.setGeometry(p1.vb.sceneBoundingRect())

    ## need to re-update linked axes since this was called
    ## incorrectly while views had different shapes.
    ## (probably this should be handled in ViewBox.resizeEvent)
    p2.linkedViewChanged(p1.vb, p2.XAxis)
    p3.linkedViewChanged(p1.vb, p3.XAxis)


updateViews()
p1.vb.sigResized.connect(updateViews)

p1.plot([1, 2, 4, 8, 16, 32], name='White plot')

# Create second curve
curve2 = pg.PlotCurveItem([10, 20, 40, 80, 40, 20], pen='b', name='Blue plot')
# Add curve2 into plot legend
legend.addItem(curve2, curve2.name())
# Add plot
plot2 = p2.addItem(curve2)

# Same deal for another curves ...
curve3 = pg.PlotCurveItem([3200, 1600, 800, 400, 200, 100], pen='r', name='Red plot')
legend.addItem(curve3, curve3.name())
p3.addItem(curve3)

## Start Qt event loop unless running in interactive mode or using pyside.
if __name__ == '__main__':
    import sys

    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

Answered By - Domarm