Create a demo notebook that combines ipywidgets, bokeh and declarative widgets about declarativewidgets

[wellecks]

Working on this

[wellecks]

As a first step, I'm working on a basic examples notebook, with an example analogous to this ipywidgets example

Bokeh contains a push_notebook() function that allows a plot's data to be updated from code run in the notebook. The function sends a display_data message that causes the update to happen.

The function is running successfully with urth-core-function and sending the message, but it's not updating the plot. Currently investigating why the update works for ipywidgets interact, but not urth-core-function

[wellecks]

The cause is that there is no iopub.output callback associated with the comm_msgs that our widgets send. Usually (e.g. with ipywidgets, or normal code execution), the iopub.output callback will inject the display_data message contents into a code cell.

Bokeh's push_notebook() works by sending javascript in the display_data message that updates the plot. Since our widgets don't inject display_data message contents due to lack of the iopub.output callback, the javascript isn't running.

Ipywidgets adds this callback through their View system. Each widget is associated with a client-side View, which has a handle to a cell through view.options.cell. The widget manager then constructs an iopub.output callback associated with that cell (see WidgetManager.prototype.callbacks).

However, our widgets don't use Views. As a potential workaround, we can construct the iopub.output callback using the currently selected code cell. In the case of Bokeh, it doesn't matter which output cell the display_data contents is injected to since it's just javascript that needs a place to execute. In other cases (although we haven't run into these yet), display_data contents will be injected to the currently selected cell.

tl;dr: our widgets don't have a certain callback since we don't use Views, but looks like there may be a workaround

[wellecks]

I was able to get the plot contents to display and update using urth-core-function. I put together a notebook with two simple examples showing how Bokeh and declarative widgets can be integrated. Next, I want to put together a more complex example; the first step will be choosing the theme / data to work with.

[wellecks]

It turns out there is an issue with the plot updating when more than one urth widget is declared in a single cell, so I'm looking into that now.

[wellecks]

The issue was a race condition that occurred when setting the code cell.

We can use the parent header of the execute_input to determine which cell is currently executing, and associate that cell with all of the created widgets, until a new execute_input arrives. I added a new behavior to listen for execute_input, and the current solution is to use a global lastExecutionId to track the currently executing cell. See this branch for the implementation

So far, this successfully supports multiple widgets and Run All