Implement a Signature Block Custom Form Element using a Third Party Library

Implementing a custom form element allows you to augment the existing form elements that come with Geocortex Workflow.

This article will walk you through creating a form element that uses the react-signature-pad-wrapper component to capture a user's signature.

Prerequisites#

Follow the instructions in the Web Applications SDK page to set up your development environment.

note

A working knowledge of TypeScript is recommended before extending Workflow for web-based hosts.

Overview#

Implementing a signature block custom form element for web applications using a third party library consists of the following steps:

  1. Adding third party library dependencies to your project.
  2. Creating the custom form element.
  3. Implementing the custom form element using the third party library.

Adding Dependencies#

  1. Run npm install react-signature-pad-wrapper in the terminal to install the third party react-signature-pad-wrapper component.
  2. Run npm install @types/signature_pad in the terminal to install type information for the third party component. This is optional, but it provides an improved developer experience.

Set up Custom Form Element Skeleton#

To create a new form element:

  1. Open the Workflow activity SDK in Visual Studio Code.
  2. Run npm run generate in the terminal.
  3. When prompted, select Form Element.
  4. Enter the name of the form element you would like to create and press Enter. For example, SignatureBlock.
  5. Open the newly created src/activities/SignatureBlock.tsx file.

Implement the Custom Form Element#

Modify the skeleton form element implementation in src/activities/SignatureBlock.tsx to match the following example.

src/activities/SignatureBlock.tsx
import React, { useRef } from "react";
import SignaturePadWrapper from "react-signature-pad-wrapper";
import SignaturePad, { SignaturePadOptions } from "signature_pad";
import {
CustomFormElementProps,
RegisterCustomFormElementBase,
} from "@geocortex/workflow/runtime/app/RegisterCustomFormElementBase";
/**
* A simple React Component that displays a signature input.
* @param props The props that will be provided by the Workflow runtime.
*/
const SignatureBlock = (props: CustomFormElementProps) => {
const signaturePad = useRef<SignaturePad>(null);
const handleClear = () => {
// Clear the signature.
signaturePad.current?.clear();
// Clear the value of the element and raise the changed event.
props.element.value = undefined;
props.raiseEvent("changed", undefined);
};
const handleEnd = () => {
// Get the signature from the SignaturePad component as a data URL.
const dataUrl = signaturePad.current?.toDataURL();
// Update the value of the element and raise the changed event.
props.element.value = dataUrl;
props.raiseEvent("changed", dataUrl);
};
const options: SignaturePadOptions = {
onEnd: handleEnd,
};
return (
<>
<div style={{ border: "1px solid #cccccc" }}>
<SignaturePadWrapper
height={150}
options={options}
ref={signaturePad}
/>
</div>
<button onClick={handleClear}></button>
</>
);
};
/**
* @displayName Register SignatureBlock Form Element
* @category Custom Activities
* @description Registers a Signature Block form element
*/
export class RegisterSignatureBlockElement extends RegisterCustomFormElementBase {
/** Perform the execution logic of the activity. */
execute() {
this.register("SignatureBlock", SignatureBlock);
}
}

Deploy the Form Element#

Follow the instructions to build and deploy the activity pack.

Test the Form Element#

Once your activity pack is hosted and registered, your Register SignatureBlock Form Element custom activity should appear in the activity toolbox in Geocortex Workflow Designer alongside the built-in activities.

To use your custom form element in a workflow:

  1. Add your Register SignatureBlock Form Element custom activity to your workflow so that it runs before any Display Form activities that will use the custom form element.
  2. Select the Display Form activity that you want to include your form element in.
  3. Add a Custom form element to the form.
  4. Set the Custom Type property of the Custom form element to SignatureBlock.
  5. Test your workflow.