feat: add form-js extensions blogpost

Closes #170

src/blog/2023/005-custom-form-fields.md

@@ -0,0 +1,196 @@
+---
+
+title: Create custom form components
+description: "Introducing newest form-js extension capabilities to create custom form components."
+preview_image: http://bpmn.io/assets/attachments/blog/2023/006-range-validate.png
+layout: blogpost.hbs
+slug: 2023-custom-form-components
+author:
+- Niklas Kiefer <https://github.com/pinussilvestrus>
+published: 2023-11-01 18:00
+
+releases:
+  - '[email protected]'
+
+---
+
+<p class="introduction">
+  We are excited to inform you about the latest [form-js](https://github.com/bpmn-io/form-js) improvements that add new extension capabilities to create custom form components. It is easier now to use existing form-js components in your custom renderers and provide properties panel extensions.
+</p>
+
+<!-- continue -->
+
+The ability to create custom form components was [a long-awaited feature](https://github.com/bpmn-io/form-js/issues/123). With the recent [email protected] release, we added extension features to the toolkit in the nature of common bpmn-io extension patterns.
+
+Check out [our example](https://github.com/bpmn-io/form-js-examples/tree/master/custom-components) to gather more insights about the new extension capabilities.
+
+## Define a custom form component renderer
+
+Creating and registering custom form components with a [Preact](https://github.com/preactjs/preact) component was already possible. It is now also possible to use existing core form-js components in the renderer.
+
+```javascript
+import {
+  Errors,
+  Description,
+  Label
+} from '@bpmn-io/form-js';
+
+import {
+  html
+} from 'diagram-js/lib/ui';
+
+export function RangeRenderer(props) {
+
+  // ...
+
+  return html`<div class="my-component-wrapper">
+    <${Label}
+      id=${ prefixId(id, formId) }
+      label=${ label } />
+    <div class="my-form-component">
+      // ...
+    </div>
+    <${Description} description=${ description } />
+    <${Errors} errors=${ errors } id=${ errorMessageId } />
+  </div>`;
+}
+```
+
+<div class="figure full-size">
+  <a href="https://demo.bpmn.io/form">
+    <img src="{{ assets }}/attachments/blog/2023/006-range-validate.png" alt="The custom range component in the form viewer.">
+  </a>
+
+  <p class="caption">
+    Render a custom range component into the form viewer.
+  </p>
+</div>
+
+We also added new options to a form field `config` object. For example, you can now define the default properties panel entries that should be shown in the form editor. You can also specify an icon for the form component.
+
+```javascript
+import {
+  Numberfield
+} from '@bpmn-io/form-js';
+
+RangeRenderer.config = {
+
+  /* we can even extend the configuration of existing fields */
+  ...Numberfield.config,
+  type: rangeType,
+  label: 'Range',
+  iconUrl: `data:image/svg+xml,${ encodeURIComponent(RangeIcon) }`,
+  propertiesPanelEntries: [
+    'key',
+    'label',
+    'description',
+    'min',
+    'max',
+    'disabled',
+    'readonly'
+  ]
+};
+```
+
+That's all! The component library and properties panel will be automatically updated with the new form component, and the renderer will take over the rendering of the form component.
+
+<div class="figure full-size">
+  <a href="https://demo.bpmn.io/form">
+    <img src="{{ assets }}/attachments/blog/2023/006-range-palette.png" alt="The component library with the custom range component">
+  </a>
+
+  <p class="caption">
+    The custom range component gets populated into the component library.
+  </p>
+</div>
+
+
+<div class="figure condensed-size">
+  <a href="https://demo.bpmn.io/form">
+    <img src="{{ assets }}/attachments/blog/2023/006-range-properties.png" alt="The properties panel with default entries for the custom range component">
+  </a>
+
+  <p class="caption">
+    Re-use existing properties entries.
+  </p>
+</div>
+
+Please find out more about [rendering extensions](https://github.com/bpmn-io/form-js-examples/tree/master/custom-components#add-a-custom-form-component-renderer) in our dedicated example. 
+
+
+## Create a properties panel extension
+
+We added the ability to extend the properties panel with custom entries. We mirrored the [proven provider architecture](https://bpmn.io/blog/posts/2022-new-properties-panel-foundation.html) of other bpmn.io properties panel libraries.
+
+Next to the `propertiesPanelEntries` we described above, you can create a properties provider that can add, remove, and modify existing entries.
+
+```javascript 
+export class CustomPropertiesProvider {
+  constructor(propertiesPanel) {
+    propertiesPanel.registerProvider(this, 500);
+  }
+
+  getGroups(field, editField) {
+
+    ...
+    return (groups) => {
+
+      if (field.type !== 'range') {
+        return groups;
+      }
+
+      const generalIdx = findGroupIdx(groups, 'general');
+
+      groups.splice(generalIdx + 1, 0, {
+        id: 'range',
+        label: 'Range',
+        entries: RangeEntries(field, editField)
+      });
+
+      return groups;
+    };
+  }
+}
+```
+
+<div class="figure full-size">
+  <a href="https://demo.bpmn.io/form">
+    <img src="{{ assets }}/attachments/blog/2023/006-range-custom-entries.png" alt="Custom properties panel entries for the range component">
+  </a>
+
+  <p class="caption">
+    Custom properties panel entries for the range component.
+  </p>
+</div>
+
+Find out more about [properties panel extensions](https://github.com/bpmn-io/form-js-examples/tree/master/custom-components#add-custom-properties-panel-entries) in our dedicated example.
+
+
+## Plugging everything together
+
+You can plug your custom modules into the different form-js components as `viewerAdditionalModules` and `editorAdditionalModules`. With the latest release, we also added the `additionalModules` option that allows you to provide extensions to both simultaneously, for example, the renderer.
+
+
+```javascript
+import { FormPlayground } from '@bpmn-io/form-js';
+
+new FormPlayground({
+  container,
+  schema,
+  data,
+  additionalModules: [
+    RenderExtension
+  ],
+  editorAdditionalModules: [
+    PropertiesPanelExtension
+  ]
+});
+```
+
+## Wrapping Up
+
+We'd love to hear your feedback on the new extension capabilities. We are looking forward to seeing what you build upon the new features!
+
+Did we miss anything? Did you spot a bug, or would you like to suggest an improvement? Reach out to us via [our forums](https://forum.bpmn.io/), tweet us [@bpmn_io](https://twitter.com/bpmn_io), or file an issue you found in [the form-js issue tracker](https://github.com/bpmn-io/form-js/issues).
+
+Get the latest Forms modeling toolkit pre-packaged or as source code via [npm](https://www.npmjs.com/package/@bpmn-io/form-js) or [unpkg](https://unpkg.com/@bpmn-io/form-js).