Placement of label relative to figure

I’m trying to create a figure where I have labels in the lower left and upper left corners with some informational text. Creating a label in the lower left corner is simple enough, but how do I create one in the upper left corner when the plot is set to be dynamically scaled based on the screen size of the device rendering it? I can’t specify a y-coordinate in screen coordinates because I don’t know how large the plot will be beforehand. I also don’t want to specify one in data coordinates because I want the label to stay in the upper left corner when zooming in or panning around.

Below is a minimal script with the two labels and some filler data:

from bokeh.plotting import figure, show
from bokeh.models import Label

fig = figure(title='Label position test')
fig.sizing_mode = 'stretch_both'

fig.circle([1, 2, 3, 4, 5], [6, 7, 2, 4, 5], size=20, color="navy", alpha=0.5)

lower_left = Label(x=5, y=5, x_units='screen', y_units='screen', text='Lower left corner')
fig.add_layout(lower_left)

# How can I position this relative to the upper bound of the figure?
upper_left = Label(x=5, y=500, x_units='screen', y_units='screen', text='Upper left corner')
fig.add_layout(upper_left)

show(fig)

You can specify a negative value, which is offset from the opposite side.

You mean by doing this?

upper_left = Label(x=5, y=-5, x_units='screen', y_units='screen', text='Upper left corner')

That produces the following plot for me:

Screenshot from 2022-07-04 20-56-471366×768 44.2 KB

I’m not sure if something changed at some point or if my memory is just bad on this point. Looking at the code, it does not behave that way after all. I don’t have any simple workarounds to suggest either, unfortunately. You would have to do something like set up a range callback and update the label y-position whenever the range changes.

Please feel free to open a GitHub Issue about supporting this use-case.

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