silx.gui.plot.PlotWidget: fix resetting zoom for curves/scatters to take the visible data in the X-range into acount

[woutdenolf]

• The PR title is formatted as: <Module or Topic>: <Action> <Summary> (see contributing guidelines)

PR summary

• Item.getBounds() now returns a named tuple Bounds instead of tuple
• Item.getResetBounds() introduced for the bounds used when resetting the zoom (current axes autoscale and limits properties have an effect on the returns Bounds)

AI Disclosure

• AI tool(s) chatgpt used for adding the fix to PlotWidget based on https://silx.readthedocs.io/en/latest/_modules/silx/gui/plot/PlotWidget.html#PlotWidget

Before this PR: reset zoom takes entire X-range to determine Y-range

After this PR: reset zoom takes current X-range to determine Y-range

Code for the example

import sys
import numpy

from silx.gui import qt
from silx.gui.plot import PlotWindow

app = qt.QApplication(sys.argv)

plot = PlotWindow()

x = numpy.linspace(0, 100, 5000)

y_left_main = numpy.sin(x * 0.2)
y_left_main += 5 * numpy.exp(-0.5 * ((x - 50) / 0.5) ** 2)

y_right = 0.5 * numpy.cos(x * 0.2)
y_right += 200 * numpy.exp(-0.5 * ((x - 85) / 0.2) ** 2)

y_left_extra = 0.3 * numpy.cos(x * 0.5)
y_left_extra += 8 * numpy.exp(-0.5 * ((x - 50) / 0.4) ** 2)

plot.addCurve(x, y_left_main, legend="left_main", yaxis="left")
plot.addCurve(x, y_left_extra, legend="left_extra", yaxis="left")
plot.addCurve(x, y_right, legend="right_hidden_spike", yaxis="right")

plot.show()

print("")
print("=== REPRO STEPS (#179) ===")
print("1. Zoom X to [40, 60]")
print("2. Disable X autoscale (lock X axis)")
print("3. Click Reset Zoom")
print("")
print("EXPECTED:")
print("- Y limits based ONLY on visible region (x in [40, 60])")
print("- Spike at x≈85 must NOT influence autoscale")
print("")
print("BUG (before fix):")
print("- Y axis explodes due to hidden spike at x≈85")
print("")

sys.exit(app.exec())

[woutdenolf]

I added Item.getAutoScaleBounds in analogy to Item.getBounds. Then PlotWidget uses getAutoScaleBounds when resetting the zoom with at least one fixed axis.

Another example, this time a scatter plot:

import sys
import numpy

from silx.gui import qt
from silx.gui.plot import PlotWindow
from silx.gui.colors import Colormap


app = qt.QApplication(sys.argv)

plot = PlotWindow()

# visible clusters
x = 50 + 7 * numpy.random.randn(80)
y = 1.0 + 5 * numpy.random.randn(80)
values = numpy.random.rand(len(x))
item = plot.addScatter(x, y, values, legend="A", colormap=Colormap("red"))

x = 65 + 2 * numpy.random.randn(80)
y = 2.0 + 10 * numpy.random.randn(80)
values = numpy.random.rand(len(x))
item = plot.addScatter(x, y, values, legend="B", colormap=Colormap("green"))

# offscreen cluster after zoom
x = 85 + 3 * numpy.random.randn(40)
y = 50 + 2 * numpy.random.randn(40)
values = numpy.random.rand(len(x))
item = plot.addScatter(x, y, values, legend="C", colormap=Colormap("blue"))

plot.resetZoom()

plot.show()
sys.exit(app.exec())

[t20100]

Fix in YRightAxis._getDataRange should be ranges.yright instead of ranges.y, otherwise LGTM!

Haven't saw the draft mode, removing approval

[woutdenolf]

Another example for histograms

import sys
import numpy

from silx.gui import qt
from silx.gui.plot import PlotWindow

app = qt.QApplication(sys.argv)

plot = PlotWindow()

rng = numpy.random.default_rng(42)

# Main population around x=50 (visible after zoom)
data_visible = rng.normal(loc=50, scale=2, size=5000)

# Strong population around x=85 (outside zoom window)
data_hidden = rng.normal(loc=85, scale=0.5, size=30000)

plot.addHistogram(
    histogram=numpy.histogram(data_visible, bins=80)[0],
    edges=numpy.histogram(data_visible, bins=80)[1],
    legend="visible_peak",
)

plot.addHistogram(
    histogram=numpy.histogram(data_hidden, bins=80)[0],
    edges=numpy.histogram(data_hidden, bins=80)[1],
    legend="hidden_peak",
)

plot.show()

print("")
print("=== HISTOGRAM RESETZOOM TEST ===")
print("1. Zoom X to [40, 60]")
print("2. Disable X autoscale")
print("3. Click Reset Zoom")
print("")
print("EXPECTED:")
print("- Y autoscale uses only visible histogram bins")
print("- Peak around x≈85 must not contribute")
print("")

sys.exit(app.exec())

[woutdenolf]

Another example for images

import sys
import numpy

from silx.gui import qt
from silx.gui.plot import PlotWindow

app = qt.QApplication(sys.argv)

plot = PlotWindow()

image = numpy.random.normal(size=(300, 300))

# bright hotspot in center
image[140:160, 140:160] += 10

# huge hotspot far away
image[250:260, 250:260] += 100

plot.addImage(image)

plot.show()

print("")
print("=== IMAGE AUTOSCALE TEST ===")
print("1. Zoom around the center hotspot")
print("2. Disable X autoscale")
print("3. Click Reset Zoom")
print("")
print("EXPECTED:")
print("- Y limits follow visible image region")
print("- Far hotspot should not affect autoscale")
print("")

sys.exit(app.exec())

[woutdenolf]

Another example for BoundRect (not sure how to visualize)

import sys

from silx.gui import qt
from silx.gui.plot import PlotWindow
from silx.gui.plot.items.shape import BoundingRect

app = qt.QApplication(sys.argv)

plot = PlotWindow()

# Visible bounding region
rect_visible = BoundingRect()
rect_visible.setBounds((45, 55, 10, 20))
plot.addItem(rect_visible)

# Hidden bounding region
rect_hidden = BoundingRect()
rect_hidden.setBounds((80, 90, 100, 200))
plot.addItem(rect_hidden)

plot.show()

print("")
print("=== BOUNDINGRECT RESETZOOM TEST ===")
print("1. Zoom X to [40, 60]")
print("2. Disable X autoscale")
print("3. Click Reset Zoom")
print("")
print("EXPECTED:")
print("- Y limits become [10, 20]")
print("- BoundingRect at x=[80,90] must not contribute")
print("")

sys.exit(app.exec())

[woutdenolf]

Another example for axis extents (not sure how to visualize)

import sys

from silx.gui import qt
from silx.gui.plot import PlotWindow
from silx.gui.plot.items import XAxisExtent, YAxisExtent

app = qt.QApplication(sys.argv)

plot = PlotWindow()

# Visible extents
x_visible = XAxisExtent()
x_visible.setRange(45, 55)
plot.addItem(x_visible)

y_visible = YAxisExtent()
y_visible.setRange(45, 55)
plot.addItem(y_visible)

# Hidden extents
x_hidden = XAxisExtent()
x_hidden.setRange(80, 90)
plot.addItem(x_hidden)

y_hidden = YAxisExtent()
y_hidden.setRange(80, 90)
plot.addItem(y_hidden)

plot.show()

print("")
print("=== EXTENT RESETZOOM TEST ===")
print("")
print("CASE A: X fixed")
print("1. Zoom X to [40, 60]")
print("2. Disable X autoscale")
print("3. Click Reset Zoom")
print("")
print("EXPECTED:")
print("- Y limits become [45, 55]")
print("- YAxisExtent [80,90] ignored")
print("")
print("CASE B: Y fixed")
print("1. Zoom Y to [40, 60]")
print("2. Disable Y autoscale")
print("3. Click Reset Zoom")
print("")
print("EXPECTED:")
print("- X limits become [45, 55]")
print("- XAxisExtent [80,90] ignored")
print("")

sys.exit(app.exec())

[woutdenolf]

@t20100 @payno The Item.getBounds() and the new Item.getResetBounds() return NaN on the y limits for XAxisExtent and NaN on the x limits for YAxisExtent.

When resetting the zoom we now call Item.getResetBounds() instead of Item.getBounds() but I have I need a way to handle the NaNs because we set all 4

class BackendBase:
    def setLimits(self, xmin, xmax, ymin, ymax, y2min=None, y2max=None):

In this case it seems that instead of [nan, nan] we have [1, 100] somehow.

I can either do this: uncomment https://github.com/silx-kit/silx/pull/4633/changes#diff-73bf8890a30feb0887556785fbfd8cbdc73ea4aca5e81db9de86907c4e42dd3bR942-R943

Or BackendBase.setLimits should handle NaN. What do you think?

[t20100]

• BoundRect and ?AxisExtent are invisible items that contributes to the "data ranges" to influence reset zoom. With them, one can ensure a given plot area is visible when reseting the zoom even if no data is display there, e.g. for a 2d scatter updating live which you know the final size from the start. AFAIR they were added for flint.

• [1, 100] is the fallback axis range when limits are not valid.

I can either do this: uncomment Or BackendBase.setLimits should handle NaN. What do you think?

How it's done in PlotWidget._updateDataRange (

silx/src/silx/gui/plot/PlotWidget.py

Line 841 in 71cb9b8

def _updateDataRange(self):

) is similar to uncommenting the 2 lines in pack, so I would go this way.

BTW, it should be possible to put some code in common between _updateDataRange and _getResetDataRange (I prefer the implementation in _getResetDataRange).

[woutdenolf]

This is no longer true, we do take autoscale into account.

The difference between resetZoom and _forceResetZoom is not really clear from the docstrings. I'm not entirely sure about the original purpose either. As far as I understand

• When at least one axis is autoscaling, resetZoom calls _forceResetZoom and afterwards forces limits, except if both are autoscaling. Weird.
• When none of the axes are autoscaling, resetZoom does nothing.

[woutdenolf]

If I were to describe the new behavior of _forceResetZoom it would be this

Reset the plot limits and redraw the plot.

The plot limits after a reset depend on whether axes have

- fixed limits (autoscale=False) or
- auto-scaling limits (autoscale=True).

See :meth:`getXAxis`, :meth:`getYAxis` and :meth:`Axis.setAutoScale`.

Axes that have fixed limits keep their limits after a reset.

Axes that have auto-scaling limits will have new limits determined by

- the data range within the limits of the axes with fixed limits or
- the full data range if all axes have auto-scaling limits.

Extra margins can be added around the data inside the plot area
(see :meth:`setDataMargins`).
Margins are given as one ratio of the data range per limit of the
data (xMin, xMax, yMin and yMax limits).
For log scale, extra margins are applied in log10 of the data.

This is exactly the same for resetZoom except that when non of the axes are auto-scaling, nothing happens. It also does a thing related to log-scale an limits >=0. I'm wondering whether this should not go to _forceResetZoom or even Item.getResetBounds().

[woutdenolf]

@t20100 You created _forceResetZoom in #1312. Not clear why. It used to be resetZoom only.

[woutdenolf]

I would be inclined to just have

def resetZoom(self, dataMargins = None):
    return self._resetZoom(dataMargins=dataMargins, force=False)

def _resetZoom(self, dataMargins = None, force = True):
    ...

and all the logic happens in _resetZoom (currently _forceResetZoom), including to forcing and log-scale handling.

[woutdenolf]

I'm not sure why force would not always be True.

When all axes have autoscale=False we could just skip for performance reasons. But since "force" exists there must be other things that could influence the resetting even when autoscale=False for all. Something related to changing the aspect ratio fixing.

[woutdenolf]

Ok these is also _notifyLimitsChanged. This code is really convoluted.