Panel does not update hv.Image alpha when using .grid() and dynamic maps

Hi All,

I’m using holoviews 1.12.5 and panel 0.6.2 on linux to produce this bug.

When using a panel slider widget to change the alpha of an overlay image, the active image does not change alpha if it is a dynamic map within a GridSpace. If the images are not dynamic, or are not using .grid(), the slider acts as expected. Here is a code segment that should reproduce this issue:

import xarray as xr
import holoviews as hv
import panel as pn
hv.extension('bokeh')

image = np.random.randint(0, 256, size=(2,3,10,100,100))
mask = np.random.randint(0, 256, size=(2,3,10,100,100))

# make xarray dataset to hold images
ds = xr.Dataset({'image':(['subject', 'sequence', 'z', 'x', 'y'], image),
                 'mask':(['subject', 'sequence', 'z', 'x', 'y'], mask)},
                coords={'subject': ['a', 'b'],
                       'sequence': ['1', '2', '3'],
                       'x': list(range(100)),
                       'y': list(range(100)),
                       'z': list(range(10))}
               )

# make slider
slider = pn.widgets.FloatSlider(start=0, end=1, value=0.5, name='mask_slider')

# make hv datasets and images
hv_ds = hv.Dataset(ds)
hv_ds_image = hv_ds.to(hv.Image, kdims=['x', 'y'], vdims='image', dynamic=True).opts(cmap='Blues')
hv_ds_mask= hv_ds.to(hv.Image, kdims=['x', 'y'], vdims='mask', dynamic=True).opts(cmap='Reds').apply.opts(alpha=slider.param.value)

# make grid on 'sequence' coord, implicit groupby for 'z' and 'subject'
grid = (hv_ds_image*hv_ds_mask).grid('sequence')

#return the panel Column
pn.Column(slider, grid)

Changing the slider does not affect the current active images, but will affect any images that have not yet been viewed. Once they are viewed, they are “locked in” to that value of alpha and will no longer change.

[philippjfr]

The issue is now fixed.

[philippjfr]

Thanks for this, looks like something happens during the overlay operation.