Plotly layout callbacks get dropped when rendering FigureWidget

[simeonschwarzenberg]

Hi, im trying to get plotlys layout callbacks working with python shiny. Currently installing an on_change callback on the FigureWidgets layout will not persist to the rendered widget.

Now I've tracked down the problem to be coming from this assignment widget.layout = layout in line 193 of ~shinywidgets._render_widget_base.render_widget_base.set_layout_defaults. This somehow gets rid of the callbacks installed on the widgets layout (I've checked with print(widget.layout._change_callbacks)). This should just be a case of using plotlys own update_layout function if the widget is a plotly FigureWidget. For me replacing the assignment with the following snippet made the callbacks persist and work:

from plotly.basewidget import BaseFigureWidget
if isinstance(widget, BaseFigureWidget):
    widget.update_layout(layout)
else:
    widget.layout = layout

As a simple example application i used this:

from shiny import App, ui
from shinywidgets import render_plotly, output_widget
import numpy as np
import plotly.graph_objs as go

app_ui = ui.page_fluid(
    output_widget("plot")
)

def server(input, output, session):
    @render_plotly
    def plot():
        x = np.linspace(0, 10, 100)
        y = np.sin(x)
        fig = go.Figure(data=go.Scatter(x=x, y=y, mode="lines"))
        fw = go.FigureWidget(fig)
        fw.layout.on_change(_update_x_range, "xaxis.range")
        return fw

    def _update_x_range(layout, x_range):
        print(x_range)

app = App(app_ui, server)
if __name__ == "__main__":
    app.run()

[cpsievert]

Thanks for the report and detailed write up! Would you like to contribute a PR?

[simeonschwarzenberg]

I've created a PR.
I noticed, that there still exist some issues in newer plotly versions, although i assume these issues to be coming from plotly itself. I ran my example application with plotly v5.24.1 and i get an initial callback execution when the plot is first initialized, which is exactly what i want. Switching to plotly v6.2.0 i dont get an initial call anymore. Also a callback installed on the layout width (fw.layout.on_change(_update_width, "width")) doesn't seem to trigger, although it persists to the rendered widget. Any ideas what the issue could be?

[cpsievert]

Thanks, your PR looks great! And, it seems like on_change() doesn't do what you're wanting for width because it won't fire when the width is responsive (i.e., sized according to it's parent container element's size). I think that would be something that should be addressed in plotly itself.

Anyway, here's a little reprex to demonstrate that it does indeed fire if you're setting a the width to a fixed value:

from shiny import reactive
from shiny.express import ui, input
from shinywidgets import render_plotly, output_widget
import numpy as np
import plotly.graph_objs as go

ui.input_slider("width", "Width", min=100, max=1000, value=500)

@render_plotly
def plot():
    x = np.linspace(0, 10, 100)
    y = np.sin(x)
    fig = go.Figure(data=go.Scatter(x=x, y=y, mode="lines"))
    fw = go.FigureWidget(fig)
    fw.layout.on_change(_update_width, "width")
    return fw

@reactive.effect
def _():
    plot.widget.update_layout({"width": input.width()})


def _update_width(layout, width):
    print(width)