plotly / plotly/plotly.py

go.images moved around dcc.graph in combination with plotly.make_subplots()

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bug P3
Dominant language
Python
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Description

First off, I have also addressed this in the plotly community website, but I feel like this is the place it should be posted.

EDIT: I realize it might be better suited in the dash github. Let me know if I need to move it.

There is a bug in plotly when using dcc.Graph in combination with a subplot figure consisting of go.Images the go.Images get moved around after the user changes the number of rows of plotly.make_subplots().
For example, when I first choose to plot 5 images beneath each other, the plot will look fine, plotting five images closely together (chosen first). However, when the user subsequently chooses to plot 2 points, the images will be plotted in the same space the five images were. Similarly, when the user first chooses to plot 2 images the image looks fine. Subsequently, when the user plots 5 images, they all get messed up.

This does not happen when plotting, for example, scatter plots. Moreover, adding subtitles to the plot shows that the subtitles do not get moved around either. Using fig.show() on the figures also gives a good figure.

You can use the code below to get a minimal working example.
Moreover, using fig.show() also shows the images in their correct spaces. I believe this is a problem with dcc.graph in combination with subplots using go.Image.

from dash import Dash, dcc, html
from dash.dependencies import Input, Output
import plotly.graph_objects as go
import dash.exceptions
import numpy as np
from plotly.subplots import make_subplots
import plotly.express as px

def create_fig(n_rows):
    fig = make_subplots(n_rows, 1)

    for i in range(n_rows):
        fig.add_trace(go.Image(z=np.random.randint(0, 255, size=(60, 60, 3))), i+1, 1)
        #fig.add_trace(go.Scatter(x=[1, 2], y=[2, 4]), i + 1, 1)

    fig.update_layout(autosize=True,
                      width=100,
                      height=n_rows*100,
                      margin=dict(l=0, r=0, b=0, t=0)
                      )
    print(fig.layout)
    return fig


app = Dash(__name__)
app.layout = html.Div(
    [dcc.Graph(id='graph', style={'overflow':'scroll'}),
     dcc.Input(value=0, id='input', type='number')])


@app.callback(Output('graph', 'figure'), Input('input', 'value'))
def create_graph(n_rows):
    if n_rows == 0:
        raise dash.exceptions.PreventUpdate("Prevent update")
    else:
        if n_rows is not None:
            return create_fig(int(n_rows))


if __name__ == '__main__':
    app.run_server(debug=True)

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running the minimal Dash example, focusing on the dcc.Graph callback, create_fig, make_subplots, and go.Image traces while changing the input between two and five rows. Compare the updated figure with fig.show() and the scatter and subtitle cases. Done means images remain in their correct subplot spaces after the number of rows changes.

Written by the indexing model from the issue text.

Assessment

Tech stack
numpy, python
Domain
data-visualization, frontend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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