Check out https://developer.mozilla.org/en-US/docs/Mozilla/Debugging/Layout_Debugger. I expect it gets the information that you're looking for.
-Jeff On Fri, Apr 8, 2016 at 1:38 PM, Jip de Beer <jip.de.b...@gmail.com> wrote: > Hi all, > > I would like to inspect the Frame Tree (or Render Tree: > http://www.html5rocks.com/en/tutorials/internals/howbrowserswork/#Render_tree_construction) > in real time while browsing with Firefox. > > I first tried to access this tree with JavaScript or a browser addon. It > seems that this information is not accessible at this level. With > document.elementFromPoint() or document.elementsFromPoint() in Chrome it may > be possible to re-construct the Frame Tree but this is not optimal. Another > way I tried to approach this is the re-implement the CSS stacking mechanism > in JavaScript (https://github.com/Jip-Hop/visuallyOnTop). But this is slow, > redundant and needs to be maintained as behavior changes. > > I looked around in about:config. The closest thing I found was enabling > layout.display-list.dump. With Firefox launched from the Terminal, the > display-list is dumped in real time. It's almost what I need except that this > is only output for elements visible in the viewport. I need to inspect the > entire Frame Tree. > > The next thing I tried was installing FirefoxDeveloperEdition, hoping this > version would somehow have extra tools to access this data. But it seems this > version of Firefox is oriented towards debugging websites. Dumping the Frame > Tree is probably possible when debugging the browser itself (Debugging Gecko > Core). > > I read here: > https://developer.mozilla.org/en-US/docs/Mozilla/Performance/Debugging_a_Performance_Problem#Layout_Debugging > that I could enable this functionality by defining DEBUG_FRAME_DUMP in > layout/generic/nsFrameList.h. So I downloaded the Firefox source (nightly), > built Firefox Nightly and tried to dump the Frame Tree. > > I didn't manage to dump the Frame Tree using lldb... I followed these guides: > http://mcc.id.au/blog/2014/01/lldb-gecko > https://developer.mozilla.org/en-US/docs/Mozilla/Debugging/Debugging_on_Mac_OS_X > https://developer.mozilla.org/en-US/docs/Mozilla/Debugging/Debugging_Mozilla_with_lldb > I tried with Firefox, FirefoxDeveloperEdition and the nightly build (ran lldb > from Terminal as well as Xcode). > I was able to attach lldb to the browser, but not output a Frame Tree dump. > The code for the nightly build was unmodified. When I tried to define > DEBUG_FRAME_DUMP in layout/generic/nsFrameList.h (by uncommenting a block of > code) the build failed. > I noticed when debugging with lldb, the browser hangs until I quit lldb. I > want to dump and inspect the Frame Tree in real time. So locking the browser > with a debugger like lldb may not be the way to go after all. > > So what are the possibilities for dumping the Frame Tree in real time? It > would be awesome if it could be done from JavaScript in the browser (without > being super slow), but logging to a file or outputting to the Terminal in > real time are also acceptable solutions. Also it would be great if it's > available from the default Firefox or FirefoxDeveloperEdition apps, as it > feels like a lot of trouble to make custom builds and edits to enable this > functionality. > > I'm using the latest versions of Firefox on Mac OS X 10.10. > > Looking forward to your replies. > > Thanks in advance. > Jip > _______________________________________________ > dev-platform mailing list > dev-platform@lists.mozilla.org > https://lists.mozilla.org/listinfo/dev-platform _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
