Web development

On this page

Note

Checkout webOS official documentation

DevTools

Web applications on webOS can be inspected using Chromium DevTools, equivalent to the functionality present in modern browsers.

This can be accessed using various methods:

  1. Running ares-inspect APPID with SDK set up
  2. Directly accessing http://TV_IP:9998 from a browser (equivalent to method 1, but does not require SDK)
  3. Adding TV_IP:9998 as a "Remote Target" in chrome://inspect in Chromium-based browsers.

All these methods have some limitations on older webOS versions. For example, using methods 1 and 2 on webOS 3.8:

  • DevTools fails completely when opened in Chromium 96 (only top tab bar is rendered)
  • "Console" is not scrollable and code cannot be injected when running in Firefox 94
  • Works mostly fine in Midori 9.0 (WebKitGTK-based browser on Linux)

Option 3 works fine, but code execution in the "Console" tab does not work and the preview window seems corrupted. This also may sometimes trigger a WAM crash for unknown reasons.

Chromium versions

Some of the issues encountered using DevTools on older webOS versions may be resolved by using an older release of Chromium. Specifically, according to LG's App Debugging documentation, the supported versions are:

  • webOS 1–3: Chrome 38
  • webOS 4–5: Chrome 68
  • webOS 6+: latest version

The LG documentation links to these Chrome builds:

Undocumented features

Input/TV embedding

Web apps can embed connected external input sources in their DOM:

<video autoplay style="width:50%;height:50%">
  <source type="service/webos-external" src="ext://hdmi:1"></source>
</video>

Supported sources: ext://hdmi:1, ext://hdmi:2, ext://hdmi:3, ext://hdmi:4, ext://comp:1, ext://av:1, ext://av:2. Additionally, a TV stream can be embedded with src="tv://" and type="service/webos-broadcast"

It seems like only a single external input can be displayed at the same time (though this may be hardware-dependent).

This also partially works in the system browser (content is cut off whenever the status bar is visible), but one probably should not rely on this.

Userscripts in apps

JavaScript present in webOSUserScripts/userScript.js will be loaded as a userscript in app webviews / frames, including frames in origins outside of app root.

Example application that uses this: webosbrew/youtube-webos

Inspecting non-developer apps

Apps installed from the Content Store (generally found under /media/cryptofs) are not inspectable by default. You can make an app inspectable by adding "inspectable":true to its appinfo.json.

Inspecting system apps

It is possible to inspect system apps (i.e., those found in /usr/palm/applications) on port 9999. However, this is not enabled by default. While creating the file /var/luna/preferences/debug_system_apps should enable it, our current method of maintaining root access creates issues that require additional workarounds.