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Working with Browser

Console API messages

  • EMBED_CONSOLE=1 environment variable be used to log messages to terminal / journal
  • Simply execute browser with EMBED_CONSOLE=1
    EMBED_CONSOLE=1 sailfish-browser
  • Errors in JavaScript etc are logged


Building with logging enabled

  • Logging is only available on development gecko builds. By default xulrunner builds as release for performance reasons.
  • To switch to a development build, append an ‘a’ to the ‘milestone’ define in the RPM SPEC file.
  • The lib directory will also gain the ‘a’. If you don’t want to rebuild the other packages to link against the new path, create a symlink to this from the normal path.

Enabling module log output

  • Environment variable MOZ_LOG is used to enable logging for various modules
  • A comma separated list with verbosity
  • Verbosity levels are: 0 = Disabled, 1 = Error, 2 = Warnings, 3 = Info, 4 = Debug, 5 = Verbose
  • EmbedLite and EmbedLiteTrace are log components of embedlite
  • There is no option to turn all logging on, so explicit module names must be found in the source (grep for LazyLogModule).
  • For instance “Layers” can be used to analyze problems related to composited layers
  • Example
    MOZ_LOG="AudioStream:5,MediaFormatReader:5,MediaSource:5" sailfish-browser
  • Useful module names
    • nsComponentManager - Component loading and unloading
    • GMP - Gecko Media Plugin activity
    • PlatformDecoderModule - system codecs such as ffmpeg

Debugging User-Agent problems

  • Current user-agent is “Mozilla/5.0 (Mobile; rv:78.0) Gecko/78.0 Firefox/78.0”
  • User-agent string can be overriden site specifically
  • Debug user agents with CUSTOM_UA environment variable
  • Input for the over the air updates is located in browser’s git repository
  • There can be full user agents and replacements done with regular expression to fix user-agent strings
  • Example fix for slashdot user-agent

Debugging omni.ja of gecko

mkdir /home/<user>/omni-mytest
cd /home/<user>/omni-mytest
cp /usr/lib/xulrunner-qt5-60.9.1/omni.ja .
unzip omni.ja
rm omni.ja

# Edit jsm or js file or copy over from your close

zip -qr9XD omni.ja *
devel-su mv omni.ja /usr/lib/xulrunner-qt5-60.9.1/

# If you need to revert omni changes just have a backup of your omni.ja or reinstall xulrunner package

Partial builds

Gecko takes a long time to build, even if only a couple of source files have been modified. Luckily there is a way to build part of the tree and reconstruct a with that, which can be done much more quickly. The new library can be copied over to a device and directly replace the installed version. The compiled library will be huge as it contains all the debug symbols, so run strip on it before you copy it over.

Enter the build environment:

mb2 build-shell

Build the new library

source `pwd`/obj-build-mer-qt-xr/rpm-shared.env
make -j16 -C `pwd`/obj-build-mer-qt-xr/<path to rebuild>
make -j16 -C `pwd`/obj-build-mer-qt-xr/toolkit
strip obj-build-mer-qt-xr/toolkit/library/build/

If you need to get stacktraces from gdb and don’t mind a large transfer, you can skip the strip step. Then leave the build environment and copy the new library to the device:

scp obj-build-mer-qt-xr/toolkit/library/ user@device:~

Then on your device, copy the new lib to /usr/lib/xulrunner-<version>/ overwriting the previous version. Alternatively, replace the target with a symlink to the new library in your home directory, to save having to copy it every time.