Making your app a "default app" in webOS
Developers and users alike have all noticed this “Default Apps” option in the webOS launcher. Right now the only out-of-the-box option users are presented with is a choice of Google Maps or their carrier’s navigation solution (if applicable) for the default mapping software. But below the defaults for web, email, and phone, there’s a long list of file types and the default app used to open them (PDFs opened by PDF View, .WAV opened by Music, and so forth).
When the Default Apps scene appeared back in November with webOS 1.3.1, and was enabled with 1.3.5 a month later, we were all aflutter as to what that could mean for webOS. Pick your own third party dialer app (Google Voice), web browser, and more? That’d be grand. Sadly, Palm has yet to release an API for developers to set their app as an option for default apps, but that hasn’t stopped Jason Robitaille and Rod Whitby from hacking their way onto the Default Apps screen.
The addition of service calls registers an app with the Default Apps service, selecting the app as the default when no other apps present open that file type, and setting it as an option when there are already apps that open said file. For example, Robitaille’s Internalz app is registered as the default app for more than twenty different file types, and appears as an option for .TXT, with Doc View as the other and default choice. Tap on the file type, select the new apps, back swipe, and you’re good to go.
Jason does note that it's not entirely stable (thus Palm not publishing the API), and that some not-all-that clean "mimetype" registering to get Internalz to be an option for file types already defaulted by another app (e.g. a PDF viewer app would have to masquerade as PDF View to trick Default Apps into giving it the option).
Of course, it’s worth noting that because Palm has not released the APIs to performing these service calls, any app submitted (be it to the App Catalog, beta, or web distribution feeds) will be automatically and summarily rejected. But that’s not to stop developers from wishing, hoping, dreaming, and preparing. And releasing via homebrew... nudge nudge, wink wink.