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Jancy

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Advanced Settings

Buffer tab updates for this many seconds before sending

Sets a timeout that controls how long tab update messages buffers before sending them to their parent window.

Smaller values will update the UI more frequently but can increase CPU usage.

Disable renderer throttling

Prevents Chromium from lowering the priority of renderer processes for pages it deems invisible.

Requires Jancy to be restarted for the change to take effect.

Disable hardware acceleration

Disables hardware acceleration.

Requires Jancy to be restarted for the change to take effect.

Additonal plug-in directories to process on startup (seperate multiple directories with a semicolon)

Allows you to specify additional paths on your computer where Jancy will look for Jancy plug-ins on startup.

After changing this value, Jancy needs to be restarted for additional paths to be processed.

New Tabs

Enable background throttling

Controls if tabs consume less resources when they don’t have focus.

This feature can potentially affect the following things in the page:

  • animations
  • timers (which could inclue the timers the capture cart timers and queue positions)
  • Page Visibility API which is the technology used by websites to know if the tab has focus or not

In testing we noticed a perceivable difference in how frequently things such as queue positions updated when running 40+ tabs. Your mileage may vary.

Superfast domain name parsing

If checked, a shortcut will be used to parse domain names from URLs on every outgoing request and on some incomming responses. If unchecked, all URLs will be fully parsed and just the domain name will be used.

In testing, the superfast domain name parser seems to be fine. Fully parsing every URL and just using the domain name for the problem Jancy is trying to solve is overkill but the shortcut that the superfast domain name parser uses might not work in every situation.

New frame workaround

If checked, applies a bit of code that makes Jancy work better on some sites.

Changing this option only affects newly created tabs and not existing tabs.

Run tabs in preloader compatibility mode

If checked, preloaders that don’t conform to Jancy’s newer preloader spec and no longer work will continue to work.

Turning this option on will potentially increase the likelihood that the renderer processes in tabs will crash more frequently.

Generate a unqiue canvas hash per partition

If checked, each tab belonging to the same partition (ie. related tabs) will generate a unique canvas hash that might help with sites that check for uniqueness of canvas hash values.

Depending on the sophistication of the site you’re visiting, our implementation of this feature might get flagged and the site may not work.

Tab V8 caching option

Controls the v8 code caching policy used by Chromium.

  • disable code caching turns off code caching all together
  • heuristic based code caching
  • bypass code caching heuristics but with lazy compilation bypasses code caching heuristics but with lazy compilation
  • bypass code caching heuristics but with eager compilation same as above except compilation is eager

I think disabling code caching make the most sense. Since all Jancy sessions exist only in memory, any cached code would only be saved to the in-memory cache and discarded when the session goes away. Furthermore, since tabs are isolated and don’t share sessions, the cached code wouldn’t be shared amongst tabs all visiting the same website. By disabling the code caching your in-memory overhead should be lower becasue you’re not paying a tax to cache code you’re just going to discard. I haven’t done extensive testing on this so I might be wrong in some assumptions I’ve made. More info can be found here.

Tab WebRTC handling policy

  • disable non proxied udp does not expose public or local IPs. When this policy is used, WebRTC should only use TCP to contact peers or servers unless the proxy server supports UDP.
  • default public interface only exposes user’s public IP, but does not expose user’s local IP. When this policy is used, WebRTC should only use the default route used by http. This doesn’t expose any local addresses.
  • default public and private interfaces exposes user’s public and local IPs. When this policy is used, WebRTC should only use the default route used by http. This also exposes the associated default private address. Default route is the route chosen by the OS on a multi-homed endpoint.
  • default exposes public and local IPs. This is the default behavior. When this policy is used, WebRTC has the right to enumerate all interfaces and bind them to discover public interfaces.

Bypass CORS for requests to these URLs (separate multiple URLs with a semicolon)

A semicolon delimited list of URLs that if the destination of an outgoing request matches against, CORS will be disabled for.

Web Startup

A list of optional modules that can be enabled that modify the newly created tabs in some way.

Debugging

Trace web content permission calls

If checked this will cause extra debug messages to be written to the Jancy console.

Only effects new tabs created after this option is changed. Doesn’t effect any existing tabs.

Trace interaction system API calls

If checked this will cause a log message to be written to the Jancy console for all API calls to the interaction system’s API.