Widgets and parameters

A widget is a value a node's code reads that you set in a form instead of in the code: a threshold, a season, a date, a place. Python, Vega-Lite and Autark nodes have widgets. A Parameter node holds one such value for every node of the dataflow, and a selection tag hands a node the rows you selected in a chart or a map.

Add a widget

1. Open the node's Widgets tab (the toolbox icon in its header) and click Add widget.
2. Give it a name (letters, digits and underscores), a type, a label and a default. A choice, a checkbox group or a multi-select also takes its choices, and a number or a slider takes a minimum, a maximum, a step and units.
3. Drag the widget's tag from the strip above the code into the code, or click the tag to put it at the cursor. It shows as a chip; point at the chip to see the value it stands for.
4. Set the value in the Widgets tab and run the node.

The Add widget form for a slider named rain: its label, minimum, maximum, step, units and default.

A widget is a number, a slider, a text, a choice (a dropdown or radio buttons), a checkbox, a checkbox group, a multi-select, a date and time, a location (a latitude and a longitude, or a place search), a list of numbers or of texts, a range, or a text file.

A node's Widgets tab: a slider in millimetres, a checkbox group, radio buttons, a date and time, and a location with its place search.

When the node runs, each chip is replaced by its value, written in the code's language: a season chip runs as "winter" in Python, and an opacity chip as 0.5 in a Vega-Lite spec. Inside a quoted text, a chip becomes the value's text. The code saves a chip as [!! name !!].

Each widget's tag in the strip above the code, and the same widgets as chips in the code.

Values are saved with the dataflow. Changing one marks the node as needing a new run, so Run and Run All run it again. A chip whose name the node has no widget for stops the run with a message naming it.

Share a value with a Parameter node

A Parameter node holds one widget that any node of the dataflow can read, such as a period or a region that several nodes use.

1. Drag Parameter from the palette onto the canvas, give it a name, a type, a label and a default as for a widget, and click Add parameter.
2. Its tag, @name, shows under Shared in the strip above every node's code. Drag it into the code, where it shows as an amber chip.
3. Set the value in the Parameter node.

A Parameter node has no connections. It lists the nodes whose code uses it, and changing its value marks them as needing a new run. Edit renames it, and their code follows the new name. Pinned to the dashboard, it shows its value.

From the FloodScenarios dataflow: the Top-left corner Parameter node, a location, lists the three nodes whose code uses it. Beside it, a Data Loading node shows the shared tags above its code and the amber chips in it.

Hand a node what you selected

A selection tag gives a node's code the rows you selected in a view: a brush or a click in a Vega-Lite chart, or a pick or a brush in an Autark map or plot.

1. Run the view, so its rows are known.
2. In the reading node's Widgets tab, under Selections, click Add selection. Pick the view and the column that identifies its rows, such as osm_id or building_id, name the tag, and click Add selection tag.
3. Drag the tag into the code, where it shows as a peach chip.
4. Select in the view and run the node.

The chip becomes the list of the selected rows' ids:

picked = [!! selection buildings !!]
return arg[arg["osm_id"].isin(picked)]

With nothing selected, the list is empty. A new selection marks the node as needing a new run, and the ids are saved with the dataflow. A tag holds at most 10,000 ids.

From example 17: a ZIP code picked on an Autark map with a double-click, and a Python node whose code reads the picked ZIP codes through the zips selection tag, a peach chip. The node printed the one it was handed.