Jupyter Widgets (#24)

* Jupyter Widgets

* lint

* fixes

* consolidate

* refactor

* ported widget table

Author: jtpio

README.md

@@ -105,6 +105,75 @@ Limits of automatic cleanup:
 - It will not automatically remove all event listeners or timers.
 - It cannot safely revert all stateful third-party module internals.
 
+## Jupyter Widgets
+
+The kernel provides built-in support for [Jupyter Widgets](https://ipywidgets.readthedocs.io/) (`ipywidgets`-compatible). Widget classes and helpers are available under `Jupyter.widgets`; destructure the ones you need before using them:
+
+```javascript
+const { IntSlider, IntProgress, jslink } = Jupyter.widgets;
+
+const slider = new IntSlider({
+  value: 50,
+  min: 0,
+  max: 100,
+  description: 'My Slider'
+});
+const progress = new IntProgress({
+  value: 50,
+  min: 0,
+  max: 100,
+  description: 'Mirror'
+});
+display(slider);
+display(progress);
+
+slider.observe(({ new: value }) => {
+  console.log('Slider value:', value);
+}, 'value');
+
+jslink([slider, 'value'], [progress, 'value']);
+```
+
+Widgets auto-display when they are the last expression in a cell. Use the global `display()` function to display a widget explicitly, for example when assigning to a variable.
+
+### Available widgets
+
+- **Numeric**: `IntSlider`, `FloatSlider`, `FloatLogSlider`, `IntRangeSlider`, `FloatRangeSlider`, `Play`, `IntProgress`, `FloatProgress`, `IntText`, `FloatText`, `BoundedIntText`, `BoundedFloatText`
+- **Boolean**: `Checkbox`, `ToggleButton`, `Valid`
+- **Selection**: `Dropdown`, `RadioButtons`, `Select`, `SelectMultiple`, `ToggleButtons`, `SelectionSlider`, `SelectionRangeSlider`
+- **String**: `Text`, `Textarea`, `Password`, `Combobox`
+- **Display**: `Label`, `HTML`, `HTMLMath`, `Output`
+- **Button**: `Button` (with `.onClick()` handler)
+- **Color**: `ColorPicker`
+- **Layout / Style**: `Layout`, `DescriptionStyle`, `SliderStyle`, `ProgressStyle`, `ButtonStyle`, `CheckboxStyle`, `ToggleButtonStyle`, `ToggleButtonsStyle`, `TextStyle`, `HTMLStyle`, `HTMLMathStyle`, `LabelStyle`
+- **Containers**: `Box`, `HBox`, `VBox`, `GridBox`, `Accordion`, `Tab`, `Stack`
+- **Helpers**: `jslink`, `jsdlink`
+
+### Ported widget modules
+
+The widget runtime is split into files that roughly follow the upstream `ipywidgets` package structure so it is easier to track what has been ported.
+
+| Upstream `ipywidgets` file                           | Local file                                                            | Status  | Notes                                                                |
+| ---------------------------------------------------- | --------------------------------------------------------------------- | ------- | -------------------------------------------------------------------- |
+| `packages/base/src/widget.ts`                        | `packages/javascript-kernel/src/widgets/widget.ts`                    | Ported  | Kernel-side `Widget` and `DOMWidget` equivalents                     |
+| `packages/base/src/widget_layout.ts`                 | `packages/javascript-kernel/src/widgets/widget_layout.ts`             | Ported  | Layout models                                                        |
+| `packages/base/src/widget_style.ts`                  | `packages/javascript-kernel/src/widgets/widget_style.ts`              | Ported  | Shared style models, plus control-specific styles gathered here      |
+| `packages/controls/src/widget_int.ts`                | `packages/javascript-kernel/src/widgets/widget_int.ts`                | Ported  | Integer widgets, play, progress, and text inputs                     |
+| `packages/controls/src/widget_float.ts`              | `packages/javascript-kernel/src/widgets/widget_float.ts`              | Ported  | Float widgets                                                        |
+| `packages/controls/src/widget_bool.ts`               | `packages/javascript-kernel/src/widgets/widget_bool.ts`               | Ported  | Boolean widgets; related styles live in `widget_style.ts`            |
+| `packages/controls/src/widget_selection.ts`          | `packages/javascript-kernel/src/widgets/widget_selection.ts`          | Partial | Selection semantics still differ from `ipywidgets` in some cases     |
+| `packages/controls/src/widget_string.ts`             | `packages/javascript-kernel/src/widgets/widget_string.ts`             | Ported  | String and display widgets; related styles live in `widget_style.ts` |
+| `packages/output/src/output.ts`                      | `packages/javascript-kernel/src/widgets/widget_output.ts`             | Partial | Output capture is supported but not feature-complete                 |
+| `packages/controls/src/widget_button.ts`             | `packages/javascript-kernel/src/widgets/widget_button.ts`             | Partial | Button widget is present, but callback behavior differs slightly     |
+| `packages/controls/src/widget_color.ts`              | `packages/javascript-kernel/src/widgets/widget_color.ts`              | Ported  | Color picker                                                         |
+| `packages/controls/src/widget_box.ts`                | `packages/javascript-kernel/src/widgets/widget_box.ts`                | Ported  | Box, HBox, VBox, GridBox                                             |
+| `packages/controls/src/widget_selectioncontainer.ts` | `packages/javascript-kernel/src/widgets/widget_selectioncontainer.ts` | Ported  | Accordion, Tab, Stack                                                |
+| `packages/controls/src/widget_link.ts`               | `packages/javascript-kernel/src/widgets/widget_link.ts`               | Ported  | `jslink`, `jsdlink`, `Link`, and `DirectionalLink`                   |
+
+> **Note:** `jupyterlab-widgets`, `@jupyter-widgets/controls`, and `@jupyter-widgets/output` must be available in the JupyterLite deployment for the full widget set to render.
+
+See the [example notebook](examples/widgets.ipynb) for more usage examples.
+
 ### Enable or disable specific modes
 
 The two runtime modes are registered by separate plugins: