[Qt] Web Inspector: local inspector client UI becomes unresponsive on debugger pause during

• Component: Web Inspector (Deprecated)
• Status: RESOLVED FIXED

[Yury Semikhatsky]

Steps to reproduce:
1. Set a breakpoint.
2. Trigger the breakpoint.

Result:
Inspector UI is unresponsive.

[Mozhaev Grigory]

The bug still exists. I tested it on Windows and Linux platforms. It works fine with webkit from Qt-4.7.4 but doesn't work with webkit from trunk and from Qt-4.8.

I did some rough hack - removed isPaused() statement from a couple of the conditions in the following source files:

   WebCore/bindings/js/JSLazyEventListener.cpp (in ScriptValue ScriptController::executeScriptInWorld() func)
   WebCore/bindings/js/ScriptController.cpp (in JSLazyEventListener::initializeJSFunction() func)
   WebCore/bindings/js/JSEventListener.cpp (in JSEventListener::handleEvent() func)

Just like that:
   if (!script->canExecuteScripts(AboutToExecuteScript))// || script->isPaused())

and then GUI becomes partially responsive. After this I did a little bit more research and have got that:
when breakpoint paused - nothing changed in GUI, although "Debugger.paused" message sent to frontend page with success, but didn't executed (due to locked JS context). If you clicked on 'workers debug' combobox (or any other GUI part which interacts with backend) and then this method will be executed and GUI will be updated to paused state.

Hope it can help somehow.

I think that solving of this bug is very important (not just P2) - because no way to make local debug of javascript from inspector while it still there and it's very annoying for js developers who use qt-webkit.

Any clues?

[Mozhaev Grigory]

(In reply to comment #1)
> If you clicked on 'workers debug' combobox
Sorry. Ofc, I meant 'workers debug' checkbox.

[Leo Franchi]

I think I have some patches that fix this bug, though they are not ready yet for upstreaming. I will try to find some time next week for the upstreaming. Here they are:

1) Updated Websocket implementation to latest spec to work against a recent chrome/webkit browser:

https://gitorious.org/~lfranchi/webkit/lfranchis-qtwebkit/commit/93a72f2657c2a8bb6863d5d2ffe8ce6faedd4598

2) 2 fixes for hanging on breakpoint (one requires the above commit, but is easy enough to apply against trunk if you read the code)

https://gitorious.org/~lfranchi/webkit/lfranchis-qtwebkit/commit/4e104bc438c21ef63a6a4227a142d36bf2401b2e
https://gitorious.org/~lfranchi/webkit/lfranchis-qtwebkit/commit/1606e202891b856ad0fdae80288ccdbf8d6765e1

The latter two patches I hope should fix your issue. All 3 are also available as a standalone patch against qt 4.8 here:

https://github.com/ariya/phantomjs/blob/master/deploy/qt48_fix_inspector.patch

[Mozhaev Grigory]

(In reply to comment #3)

Thanks for the answer. I saw these patches, they doesn't solve current bug, since these patches are for Remote Debug, but this bug report actually is for Local Debug problem.

[Mozhaev Grigory]

(In reply to comment #1)
> I did some rough hack - removed isPaused() statement from a couple of the conditions in the following source files:
> 
>    WebCore/bindings/js/JSLazyEventListener.cpp (in ScriptValue ScriptController::executeScriptInWorld() func)
>    WebCore/bindings/js/ScriptController.cpp (in JSLazyEventListener::initializeJSFunction() func)
>    WebCore/bindings/js/JSEventListener.cpp (in JSEventListener::handleEvent() func)
> 
> Just like that:
>    if (!script->canExecuteScripts(AboutToExecuteScript))// || script->isPaused())
> 

I forgot to mention, what I also commented the following condition part:

    if (!scriptExecutionContext) // || scriptExecutionContext->isJSExecutionForbidden())
        return;

in  WebCore/bindings/js/JSEventListener.cpp (void JSEventListener::handleEvent(...) func)

[Mozhaev Grigory]

The above partial workaround works only on linux, on windows it still freezes the system. Anyone have any clues?

[Mozhaev Grigory]

(In reply to comment #3)
Thank you Leo for patches you made! We are using your patches to make remote debugging works, until local debugging will be fixed.

[Leo Franchi]

Glad that works for you partially at least. I remember now also hitting issues with local debugging, but as I only needed remote debugging I didn't spend too much time on that.

Next week i'll clean up my patches and see if I can get them committed upstream.

[Mozhaev Grigory]

(In reply to comment #8)
> Glad that works for you partially at least. I remember now also hitting issues with local debugging, but as I only needed remote debugging I didn't spend too much time on that.
> 
> Next week i'll clean up my patches and see if I can get them committed upstream.

Thanks again. Btw, it works only with last Chrome (with 'm' label in version) and only in Windows Chrome's version. Safari (on Windows and Mac) and Chrome on Mac doesn't work with patched remote debug - got 404 error and empty inspector.

[Mozhaev Grigory]

I will gladly help anyone who want to fix current bug, as I'm C++/Qt programmer. Maybe some webkit's guru give any hint or direction to where dig, it will safe a lot time.

[Leo Franchi]

Created attachment 123960 [details]
Patch

[Jarred Nicholls]

Comment on attachment 123960 [details]
Patch

This addresses remote debugging only, when this bug is primarily referring to local debugging where the JS context seems to pause for the Inspector client in addition to the Frame that's being inspected.  I suggest creating a new ticket for the remote debugger fixes.

[Leo Franchi]

(In reply to comment #12)
> (From update of attachment 123960 [details])
> This addresses remote debugging only, when this bug is primarily referring to local debugging where the JS context seems to pause for the Inspector client in addition to the Frame that's being inspected.  I suggest creating a new ticket for the remote debugger fixes.

Thanks, I obsoleted the patch. The new ticket is here:

https://bugs.webkit.org/process_bug.cgi

[Leo Franchi]

By that I meant here:

https://bugs.webkit.org/show_bug.cgi?id=77022

[Manuel Lazzari]

Not sure that what's happening in our hybrid QtWebKit app with Qt 4.8.0 compiled from source on Windows and Mac OS X is related/linked to this bug, if not please advise.

When I put a breakpoint in the javascript debugger and i trigger the breakpoint the javascript execution does stop but the debugger becames unusable/broken:

* the debugger does not seems to be in breakpoint (e.g. there are no stepper buttons like the "continue" button).

* scrolling through the javascript code causes the code div to scroll but the line numbers do not scroll anymore.

* closing the web inspector window will cause the javascript execution to continue: I suppose that the breakpoint was correctly triggered and cleared when exiting the window.

[Mozhaev Grigory]

(In reply to comment #15)
> Not sure that what's happening in our hybrid QtWebKit app with Qt 4.8.0 compiled from source on Windows and Mac OS X is related/linked to this bug, if not please advise.

This is exactly the problem for which this bugreport was made.

[Manuel Lazzari]

(In reply to comment #16)

> This is exactly the problem for which this bugreport was made.

Thanks, that's at least comfort me a little :)

[Manuel Lazzari]

Is anyone working on this? Is there any patch or workaround? How this "remote debugging" works with Qt 4.8?

[Mozhaev Grigory]

(In reply to comment #18)
> Is anyone working on this? Is there any patch or workaround? How this "remote debugging" works with Qt 4.8?

"remote debugging" works with Qt 4.8 well (with patched version or webkit), but local debugging still hasn't any workaround.

[Saulo]

It is still broken on Qt-4.8.1.

[Yaroslav Tsarko]

Created attachment 142441 [details]
Patch

Greetings everyone!

After 3 days of debugging JavaScript debugger in QtWebkit I have found the reason of Web Inspector GUI lock when debuggee page was paused. The reason itself is quite trivial: Web Inspector front-end (also written in JavaScript) was also paused along with the debuggee page itself. I suppose that this bug has been introduced by commit a2ce7739 (qtwebkit repo) when every QWebPage being created was explicitly added to PageGroup called "Default Group". When debugger pauses page it also pauses all the pages that belong to its page group. So the Web Inspector page was paused too. The applied patch fixes this problem (I`ve tested it with Qt 4.8.1 with QtWebkit 2.2.2).

[zalan]

Comment on attachment 142441 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=142441&action=review

Good catch! However you are missing changelog entry. Please look at the following page http://www.webkit.org/coding/contributing.html and submit your patch accordingly.

> Source/WebKit/qt/WebCoreSupport/InspectorClientQt.cpp:67
> +        // This leads that Web Inspector front-end is paused too leading to locked Web Inspector GUI (bugzilla ticket 71271).

No need to mention the bug# in the comment. Changelog entry should have it.

> Source/WebKit/qt/WebCoreSupport/InspectorClientQt.cpp:68
> +        handle()->page->setGroupName("__WebInspectorPageGroup__");

I'd rather have it in InspectorClient::openInspectorFrontend() where we actually open the front end, something like m_frontendWebPage->setGroupName("group_name_comes_here");

[Yaroslav Tsarko]

Created attachment 142448 [details]
Patch

Zalan,

I have recreated the patch according to your comments. Please review it and commit to the repo if it is ok.

[Jarred Nicholls]

Thanks Tsarko :)

[WebKit Review Bot]

Comment on attachment 142448 [details]
Patch

Clearing flags on attachment: 142448

Committed r117440: <http://trac.webkit.org/changeset/117440>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.

[Yaroslav Tsarko]

(In reply to comment #26)
> All reviewed patches have been landed.  Closing bug.

Is there any chance that this fix will be merged into qtwebkit (git) repository, branch qtwebkit-2.2?