LabelItem inverted in Y-axis (upside-down)

[stan-servaenergy]

Short description

LabelItem inverted in Y-axis, possibly also at wrong coordinates.

Code to reproduce

import pyqtgraph as pg

app = pg.mkQApp()
plt = pg.plot([1, 2, 3], [10, 2, 1])
lbl = pg.LabelItem(text="testing")

plt.addItem(lbl)
app.exec()

Expected behavior

Label has normal orientation.

Real behavior

Label is upside down and probably at wrong coordinates too.

Tested environment(s)

• PyQtGraph version: 0.13.3
• Qt Python binding: PySide6 6.5.2 Qt 6.5.2 (also tried 6.2.2)
• Python version: 3.11.4 (also tried 3.10)
• NumPy version: 1.24.4
• Operating system: Linux fes 6.3.3-060303-generic #202305171336 SMP PREEMPT_DYNAMIC Wed May 17 13:45:19 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
• Installation method: pip

Additional context

I need to use LabelItem instead of TextItem, because for my use case I need my plot labels to scale with plot (e.g. zoom in/out).

[pijyoi]

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

app = pg.mkQApp()
plt = pg.PlotWidget()
plt.show()

plt.plot([1, 2, 3], [10, 2, 1])

text = QtWidgets.QGraphicsSimpleTextItem("testing")
text.setBrush(QtCore.Qt.GlobalColor.white)
y = text.boundingRect().height() + 2
text.setTransform(QtGui.QTransform(1,0,0,-1,0,y))
plt.addItem(text)

# debug placement
rectitem = QtWidgets.QGraphicsRectItem(text.boundingRect())
rectitem.setPen(pg.mkPen('r', style=QtCore.Qt.PenStyle.DashLine))
plt.addItem(rectitem)

app.exec()

[stan-servaenergy]

Thank you, pijyoi for your example on how to workaround the issue. Following it, I was able to resolve LabelItem placement for my use case.

Is there anything I can help with to create a permanent fix for everyone?

[pijyoi]

Could you provide a scenario where plotting scaled text would be useful? The following snippet surely isn't one of them.

import pyqtgraph as pg
from pyqtgraph.Qt import QtCore, QtGui, QtWidgets
import numpy as np

app = pg.mkQApp()
plt = pg.PlotWidget()
plt.show()

x = np.linspace(-10,10,201)
y = np.sinc(x)
plt.plot(x, y)

text = QtWidgets.QGraphicsSimpleTextItem("testing")
text.setBrush(QtCore.Qt.GlobalColor.white)
y = text.boundingRect().height() + 2
text.setTransform(QtGui.QTransform(1,0,0,-1,0,y))
pt = QtCore.QPointF(0, 1)
text.setPos(pt)
plt.addItem(text)

# debug placement
rect = text.boundingRect()
rect.moveTo(pt)
rectitem = QtWidgets.QGraphicsRectItem(rect)
rectitem.setPen(pg.mkPen('r', style=QtCore.Qt.PenStyle.DashLine))
plt.addItem(rectitem)

app.exec()

[stan-servaenergy]

In my use case, I have a DAG (Directed acyclic graph) and use ScatterPlotItem with large size argument to display nodes as oversized "bubbles". I'm using LabelItem to place node description labels inside those "bubbles". The width of edges between nodes also conveys information.

I'm using pxMode set to False, so that "bubbles" shrink/expand as you zoom in/out. Without it I was getting "casino chip" effect of nodes staying same screen size and obscuring edges or even whole plot when zoomed out.

Perhaps this is bit abusing the components and I should have developed custom GraphItem, but initially this looked like a easy way to go.