Creating a gateway function that calls a javascript function

bmusson · August 5, 2025, 1:36pm

Yup, you can do this. See Embr-Periscope for inspiration:

On the Perspective client-side, add your own message handler to the ClientStore's connection.

clientStore.connection.handlers.set('your-protocol', (payload) => { ... } )

github.com/mussonindustrial/embr

modules/periscope/web/src/extensions/runJavaScript.ts

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          export const PROTOCOL = {
            RUN: 'periscope-js-run',
            RESOLVE: 'periscope-js-resolve',
            ERROR: 'periscope-js-error',
          }
          
          export function installRunJavaScript(clientStore: ClientStore) {
            const thisArg = clientStore
          
            clientStore.connection.handlers.set(PROTOCOL.RUN, (payload) => {
              const { function: functionLiteral, args, id } = payload
          
              function resolveSuccess(data: unknown) {
                clientStore.connection.send(PROTOCOL.RESOLVE, {
                  id,
                  success: true,
                  data,
                })
              }

On the Perspective gateway-side, trigger this message by sending a message to a Page.

page.send("your-protocol", payload)

github.com/mussonindustrial/embr

modules/periscope/gateway/src/main/kotlin/com/mussonindustrial/ignition/embr/periscope/scripting/JavaScriptFunctions.kt

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                      )
                      .exceptionally { error ->
                          originalThreadContext.view.get()?.mdcSetup()
                          page.session.sendErrorToDesigner(error.message, error)
                          page.log.error("Exception occurred executing client-side JavaScript.", error)
                          originalThreadContext.view.get()?.mdcTeardown()
                          throw error
                      }
                      .whenCompleteAsync({ _, _ -> requestsInProgress.remove(id) }, queue::submit)
          
                  page.send(JavaScriptRunMsg.PROTOCOL, message.getPayload())
              }
          
              return future
          }
          
          inner class ScriptOverloads {
              val runJavaScriptAsync =
                  PyArgOverloadBuilder()
                      .setName("runJavaScriptAsync")
                      .addOverload(