Skip to main content

Developing Userscripts for Chrome (caveats)

To develop Chrome extensions, crx is the best way. But the user scripts that are developed in general for Greasemonkey can also be delivered for Chrome, if a few easy rules are followed.

1. @required and @resource don't work.

By default, atleast for now, These two Userscript metatags donot work on Chrome. If you need to load a js file, instead of using @required - try to use document.createElement. Similarly with @resource.

2. Some GreaseMonkey helper methods don't work or are restricted.

Methods with GM_ prefix from userscript api may not work. Particularly, unsafeWindow, GM_registerMenuCommand, GM_setValue, or GM_getValue are not supported. GM_xmlhttpRequest will work but not only on the same domain.

3. @includes are not shown while installing.
This may not be a deal breaker for developers, but sure is for users. The patterns used in @include is not shown while installing. Instead a generic message is shown as below. This message may scare the users away.

image

To over come this, add @match and show the @include pattern there. The message window pics up the domain portion of the pattern.

image

This actually can be used maliciously. A developer may install a script with a different include pattern and show a different match pattern, there by luring the users to install a malicious script. Although Chrome follows the @include pattern to add script to the page. Just the installation window pops open with @match pattern. Please use this for responsibly.

Here is comments from The Chromium source that explains the reasoning, valid/invalid patterns @match can take:
// Examples of valid patterns:
// - http://*/*
// - http://*/foo*
// - https://*.google.com/foo*bar
// - file://monkey*
// - http://127.0.0.1/*
//
// Examples of invalid patterns:
// - http://* -- path not specified
// - http://*foo/bar -- * not allowed as substring of host component
// - http://foo.*.bar/baz -- * must be first component
// - http:/bar -- scheme separator not found
// - foo://* -- invalid scheme
// - chrome:// -- we don't support chrome internal URLs
//
// Design rationale:
// * We need to be able to tell users what 'sites' a given URLPattern will
//   affect. For example "This extension will interact with the site
//   'www.google.com'.
// * We'd like to be able to convert as many existing Greasemonkey @include
//   patterns to URLPatterns as possible. Greasemonkey @include patterns are
//   simple globs, so this won't be perfect.
// * Although we would like to support any scheme, it isn't clear what to tell
//   users about URLPatterns that affect data or javascript URLs, so those are
//   left out for now.

Popular posts from this blog

Being a Vegetarian

I am a Proud Vegetarian. I don't eat Meat or Eggs. People say its hard here in US to be one. I beg to differ. The mere fact that I am hail and healthy these 4 years is a definitive proof. Apart from being bullied and trash talked by The Meat-Eaters, There is really nothing that makes this choice of mine any more than a debatable issue at a lunch or dinner. Other things aside, I am writing this blog having watched a PETA Video. Before you click on the play button, I ask you - If you are a vegetarian : Dont watch it. If you are not : Dare to watch it till the end. If you think going veg is just a fashion, think again . Even if you just want to do it for Fashion . Do it. Go Vegetarian. And Feel better asking the waiter for a Vegetarian Entrée in your next lunch.

Using Equinox CommandProvider to make OSGi console interactive.

After fiddling with the First Bundles that "Hello World"-ed upon Activation, You want to see more interactivity in OSGi. Although Using OSGi for an interactive Command Line Application would be like this one would be, well, a callable over-kill, I am going to start with an example and Expand it in later posts. So, please Welcome CommandProvider. CommandProvider is an EQUINOX specific API for extending the Console. This basic Example illustrates how to get a command from console and do something in java and also gets your feet wet on Service Registry package com.so.examples.commandconsole; import org. eclipse .osgi.framework.console .CommandInterpreter; import org.eclipse.osgi.framework.console.CommandProvider; public class DisplayMessageCommand implements CommandProvider { public void _say(CommandInterpreter ci) { ci.print("You said:" + ci.nextArgument()); } @Override public String getHelp() { return "\tsay - repeats what you say\n"; } }

How to Make a Local (Offline) Repository in Ubuntu / Debian

If you are in a place where you dont have internet (or have a bad one) You want to download .deb packages and install them offline. Each deb file is packaged as a seperate unit but may contain dependencies (recursively). apt-get automagically solves all the dependencies and installs all that are necessary. Manually install deb files one by one resolving each dependency would be tedious. A better approach is to make your own local repository. Before you actually make a repo, You need *all* deb files. You dont practically have to mirror all of the packages from the internet, but enough to resolve all dependencies. Also, You have to make sure, you are getting debs of the correct architecture of your system (i386 etc) # 1. make a dir accessible (atleast by root) sudo mkdir /var/my-local-repo # 2. copy all the deb files to this directory. # 3. make the directory as a sudo dpkg-scanpackages /var/my-local-repo /dev/null > \ /var/my-local-repo/Packages # 4. add the local repo to sour