Preload Desktop Agents (next)
A Preload Desktop Agent is an FDC3 Desktop Agent (DA) supporting web applications that 'inject' or 'preload' scripts into web windows which provide access to an FDC3 Desktop Agent API implementation. This document specifies the required behavior for a Preload Desktop Agent (DA).
The getAgent() specification in the FDC3 Web Connection Protocol relies on Preload DAs behaving as specified in this document.
Injecting the global FDC3 object
Since FDC3 is typically available to the whole web application, Desktop Agents are expected to make the DesktopAgent interface available at a global level. Hence, a Preload Desktop Agent MUST provide the FDC3 API via a global accessible as window.fdc3. Implementors MAY additionally make the API available through modules, imports, or other means.
The global window.fdc3 MUST only be available after the API is ready to use. Implementors MUST provide a global fdc3Ready event that is fired when the API is ready for use.
However, implementors SHOULD also ensure that the global is made available as soon as possible after the window is created to ensure that it can be detected by getAgent(). Queuing of requests to the API MAY be used to make the API available, while initialization is underway.
Prior to FDC3 2.2, apps were advised to check for the existence of the FDC3 API at window.fdc3 and then add a listener for the fdc3Ready event if it was not found. This has since been superseded by the recommendation to use getAgent(), which handles those steps internally, alongside supporting FDC3 in web browsers ( via the Browser Resident Desktop Agent spec).