How to run JS on page load started?

[Anton Smirnov]

Hey, guys.

I'm working on some content filtering library integration and it requires some JS to be executed on page load.

It's not a spam, malware, etc - it just allows user to filter some undesired content.

For this i need to figure out how:

1) to catch "page/iframe load started" event.

URL is required for it as it will generate JS script body dynamically.

2) to launch JS

It seems that #1 happens in browser process and #2 happens in child process, is it correct?

Should i add some IPC messages?

Actually the script will subscribe to 'DOMContentLoaded' and 'load' events as it requires DOM to be built,

so probably if there is a way to subscribe to that events directly it will work too.

Any suggestions and starting points are highly appreciated. Thanks.

[PhistucK]

Why do you need C++ for that? Extensions can already do this...

☆PhistucK

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[Anton Smirnov]

Hi.

On Friday, September 1, 2017 at 1:12:34 PM UTC+5, PhistucK wrote:

Why do you need C++ for that? Extensions can already do this...

The first reason is that extensions are not supported on mobile AFAIK.

The second, some browsers have similar feature as built-in killer feature so i'd like to provide an example how the library can be integrated in chromium and forks.

 

☆PhistucK

On Fri, Sep 1, 2017 at 8:42 AM, Anton Smirnov <d...@antonsmirnov.name> wrote:

Hey, guys.

I'm working on some content filtering library integration and it requires some JS to be executed on page load.

It's not a spam, malware, etc - it just allows user to filter some undesired content.

For this i need to figure out how:

1) to catch "page/iframe load started" event.

URL is required for it as it will generate JS script body dynamically.

2) to launch JS

It seems that #1 happens in browser process and #2 happens in child process, is it correct?

Should i add some IPC messages?

Actually the script will subscribe to 'DOMContentLoaded' and 'load' events as it requires DOM to be built,

so probably if there is a way to subscribe to that events directly it will work too.

Any suggestions and starting points are highly appreciated. Thanks.

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[PhistucK]

Correct, mobile Chrome cannot run extensions.

☆PhistucK

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[PhistucK]

I think WebView can inject scripts to pages.

So I suggest you try to trace it, from the API to the renderer code that does that, using cs.chromium.org.

☆PhistucK

[Anton Smirnov]

On Monday, September 4, 2017 at 12:39:10 PM UTC+5, PhistucK wrote:

I think WebView can inject scripts to pages.

So I suggest you try to trace it, from the API to the renderer code that does that, using cs.chromium.org.

Well, yes. I could see the sources starting 'webView'.evaluateJavaScript(..) too.

I was just curious if someone can suggest a shorter way.

 

☆PhistucK

☆PhistucK

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[Андрей Кадацкий]

Hi Anton, I did some JS injections onPageLoadStarted. 
In my case case it was implemented like this:

In ChromeActivity or ChromeTabbedActivity you have TabModelSelectorTabObserver with onPageLoadStarted(Tab tab, String url){...} callback. You can get WebContents via tab.getWebContents() from it. On WebContents object you call evaluateJavaScript(String script, JavaScriptCallback callback) method, where script is string with your JS code.

[Anton Smirnov]

Hi, Andrew.

On Tuesday, September 5, 2017 at 8:11:43 PM UTC+5, Андрей Кадацкий wrote:

Hi Anton, I did some JS injections onPageLoadStarted. 
In my case case it was implemented like this:

In ChromeActivity or ChromeTabbedActivity you have TabModelSelectorTabObserver with onPageLoadStarted(Tab tab, String url){...} callback. You can get WebContents via tab.getWebContents() from it. On WebContents object you call evaluateJavaScript(String script, JavaScriptCallback callback) method, where script is string with your JS code.

Thanks for pointing the direction! What about C++ side, where an invocation to `TabModelSelectorTabObserver. onPageLoadStarted` comes from? Does it come from .RenderViewHost::OnMsgNavigate  originally?

[Андрей Кадацкий]

But why do you need to know where it invocation goes from? 

[Anton Smirnov]

I've already implemented a part of integration in C++ code (chrome_network_delegate.cc) to filter out undesired resources.

So it be be consistent to introduce changes in C++ code rather than in Java/Android.

[Anton Smirnov]

Does anyone know how to implement it in C++?

It seems that one can invoke javascript with frame's `ExecuteJavaScript(..)`.

Any suggestion on how to properly catch 'page load started' event?

[Alex Clarke]

Are you aware of DevTools Network.setRequestInterceptionEnabled?  That can filter resources. See https://chromedevtools.github.io/devtools-protocol/tot/Network/#method-setRequestInterceptionEnabled

There are C++ bindings for that in headless_lib, but it's mostly used via node.js

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[SPEC INDIA DEV]

Thanks Andrew, for much needed idea.

It worked for me but with evaluateJavaScriptForTest and not evaluateJavascript method. This solution seems to be patch. Is there any other way to make it work with evaluateJavascript.

Thanks Again