在 Spotfire Mods 中，作为阅读器的一部分，我可以确定数据视图中发生了什么变化吗？

Question

I was able to successfully implement the monitoring for changes in the dataview overall, and any mod properties as described in this answer for my D3 network chart mod in Spotfire. It works really well.

However, in a D3 network chart there is simulation running and you only want this simulation to restart when the actual data rendered changes, is there a way to check within the dataView object for more detailed changes. For example, if the axis expression changes for the Color By or Size by column I don't need to rerun the network simulation and simply update the color or size of a node, or even when some marking is applied to the network chart (which also affects the dataView). However, if my data columns change, I want the network to rerun the simulation.

Another example use case is if filtering has been applied, we may want to update the network only if a large amount of data has been filtered out.

Is there any methods in the API I could use to check these more detailed changes in the DataView passed into reader?

My reader looks like this:

/**
 * Create the read function.
 */
const reader = readerWithChangeChecker(
    mod.createReader(
        mod.visualization.data(),
        mod.windowSize(),
        mod.property("network_strength"),
        mod.property("display_labels"),
        mod.property("network_type"),
        mod.property("apply_color")
    )
);

and I have an updateNetwork function in async render function which subscribes to the reader. I then have some simple logic checks which are passed to the updateNetwork chart function:

// check what has changed
let data_requires_update = false;
let simulation_requires_update = false;
let window_requires_update = false;
let rendering_requires_update = false;

if (reader.hasValueChanged(dataView)) {
    data_requires_update = true;
    simulation_requires_update = true;
}

if (
    reader.hasValueChanged(network_strength) ||
    reader.hasValueChanged(network_type)
) {
    simulation_requires_update = true;
}

if (reader.hasValueChanged(windowSize)) {
    window_requires_update = true;
}

if (
    reader.hasValueChanged(display_labels) ||
    reader.hasValueChanged(apply_color)
) {
    rendering_requires_update = true;
}

// trigger loading network
updateNetwork(
    data_requires_update,
    simulation_requires_update,
    window_requires_update,
    rendering_requires_update
);

So I am looking to add more detail to dataView check so I can detect axes changes, main data table changes, and whether filtering has happened. Is this possible?

Answer 1

The dataview in Spotfire Mods can be invalidated and replaced due to many different reasons; new axis expressions, changed data table, changed marking or filtering, new streaming data or refreshed/replaced data tables or even modified document properties if those are used in an axis expression.

It is therefor not always possible to get detailed information as to what of these caused a new data view to be calculated, but you can subscribe to changes in the axis expressions, thereby forcing a refreshed simulation at least when the user changes any of the important axis expressions.

In your situation adding all axes but ColorBy and SizeBy may bring you closer to your goal. If you get a new dataview but no new axes, then you could try to update the visualization without refreshing the simulation using d3. If the change was for example only marking, color or size no new simulation pass should be needed. In order to identify the nodes and connections in your visualization you should use the key property of the hierarchy leaf node.

If the reason for the new dataview was for example filtering or new data (streaming or refreshed data table), you will instead have a set d3 enter/exit DOM elements. If those sets are relatively small it might be ok to not refresh the simulation?

But also bear in mind that the measures defining the connection strength could have new values even if that axis expression is unchanged. So it may be hard to know for sure that an update is ok. A manual refresh simulation button might be the easiest way out of that unless you want to compare the entire data views to come up with a way to determine whether to update or refresh it entirely.

The conclusion is that most information needed to determine whether to update the current visualization or to re-run the entire layout pass is available via the API, but to make a great responsive Mod reuires some knowledge about what is being visualized.