qtcreator调试webkit

qtreator是在ubuntu上支持gdb比较好的IDE，可以方便的单步调试，快速熟悉代码。

ubuntu上通过qtcreator调试wpewebkit，因为是通过cog启动，wpewebkit进程和cog不是同一个进程，需要通过attach的方式才能断点到Mediaplayer的代码。

配置qtcreator

先从命令行启动cog

cog --platform=x11 https://www.w3.org/2010/05/video/mediaevents.html

找到webkit进程

$ ps -ax | grep webkit
15983 pts/18   SLl+   0:00 /home/hui/disk4t/codes/wpe/source/inst/libexec/wpe-webkit-1.0/WPENetworkProcess 3 10
15994 pts/18   tLl+   2:37 /home/hui/disk4t/codes/wpe/source/inst/libexec/wpe-webkit-1.0/WPEWebProcess 8 19

增加qtcreator环境变量

LD_LIBRARY_PATH

$LD_LIBRARY_PATH:/home/hui/disk4t/codes/wpe/source/inst/lib:/home/hui/disk4t/codes/wpe/source/inst/lib/x86_64-linux-gnu

ubuntu上通过qtcreator调试webkit，因为是通过cog启动，wpewebkit进程和cog不是同一个进程，需要通过attach的方式才能断点到Mediaplayer的代码。

attach到WPEWebProcess进程

attach从qtcreator菜单进入：

Select Debug > Start Debugging > Attach to Running Application

选择15994进程，如果出现ptrace的error，需要做如下配置：

ptrace: Operation not permitted.

Could not attach to the process. Make sure no other debugger traces this process.
If your uid matches the uid
of the target process, check the settings of
/proc/sys/kernel/yama/ptrace_scope
For more details, see /etc/sysctl.d/10-ptrace.conf

将/proc/sys/kernel/yama/ptrace_scope虚拟文件的内容设为0：

echo 0 > /proc/sys/kernel/yama/ptrace_scope

这个是临时方法，重启之后失效。

设置好断点后，运行效果如下：

通过cog启动，然后attach到WPEWebProcess后，发现https://www.w3.org/2010/05/video/mediaevents.html这个测试页面在cog启动后，video标签已经完全加载，没法断点到player创建的地方。

所以又找了一个测试页面https://easyhtml5video.com/help/html-5-video-test-7.html，通过log发现，这个页面启动cog后video标签没有加载，满足条件，设置断点后成功中断。

cog启动：

cog --platform=x11 https://easyhtml5video.com/help/html-5-video-test-7.html

attach进程后的中断：

MediaPlayerPrivateGStreamer::load的调用栈：

输出log

journalctl

# 这样过滤的log不全：

journalctl -f WEBKIT_SUBSYSTEM=WPEWebKit WEBKIT_CHANNEL=Media

-- Logs begin at Mon 2021-12-27 19:51:37 CST. --
2月 11 09:54:05 hui WPEWebProcess[32009]: HTMLMediaElement::mediaPlayerPlaybackStateChanged(FE25312987F69B65) false
2月 11 09:54:05 hui WPEWebProcess[32009]: HTMLMediaElement::playInternal(FE25312987F69B65)
2月 11 09:54:05 hui WPEWebProcess[32009]: MediaElementSession::clientWillBeginPlayback(FE25312987F69B65) state = Playing
2月 11 09:54:05 hui WPEWebProcess[32009]: PlatformMediaSessionManager::setCurrentSession(0) (FE25312987F69B65)
2月 11 09:54:05 hui WPEWebProcess[32009]: PlatformMediaSessionManager::sessionWillBeginPlayback(0) (FE25312987F69B65) returning true
2月 11 09:54:05 hui WPEWebProcess[32009]: HTMLMediaElement::setAutoplayEventPlaybackState(FE25312987F69B65) StartedWithoutUserGesture
2月 11 09:54:05 hui WPEWebProcess[32009]: HTMLMediaElement::updatePlayState(FE25312987F69B65) shouldBePlaying = true, playerPaused = false
2月 11 09:54:05 hui WPEWebProcess[32009]: HTMLMediaElement::mediaPlayerVolumeChanged(FE25312987F69B65)

 # webkit
 export WEBKIT_DEBUG="Network=debug,Media=debug"
 export WEBKIT_DEBUG="all"
 
 # gstreamer
 export GST_DEBUG="3,webkit*:6"

查看journalctl日志

journalctl -ef | grep -E "WPEWebProcess|WPENetworkProcess"

MediaSource的log输出：

WPEWebProcess[2883]: MediaSource::detachFromElement(0)
WPEWebProcess[2883]: MediaSource::onReadyStateChange(0) old state = open, new state = closed
WPEWebProcess[2883]: MediaSourcePrivateGStreamer::~MediaSourcePrivateGStreamer(20E2EA6F)
WPEWebProcess[2883]: MediaSource::onReadyStateChange(0) old state = closed, new state = open
WPEWebProcess[2883]: MediaSource::setDuration(0) 8656.959
WPEWebProcess[2883]: MediaSource::setDurationInternal(0) {
    "value":8656.959}
WPEWebProcess[2883]: MediaSource::seekToTime(0) {
    "value":130}
WPEWebProcess[2883]: MediaSource::completeSeek(0) {
    "value":130}
WPEWebProcess[2883]: MediaSource::seekToTime(0) {
    "value":130}
WPEWebProcess[2883]: MediaSource::completeSeek(0) {
    "value":130}

SourceBuffer的log输出：

WPEWebProcess[2883]: SourceBuffer::SourceBuffer(62DF0001)
WPEWebProcess[2883]: SourceBuffer::SourceBuffer(62DF0002)
WPEWebProcess[2883]: SourceBuffer::~SourceBuffer(20E20002)
WPEWebProcess[2883]: SourceBuffer::~SourceBuffer(20E20001)
WPEWebProcess[2883]: SourceBuffer::sourceBufferPrivateDidReceiveInitializationSegment(62DF0001)
WPEWebProcess[2883]: SourceBuffer::sourceBufferPrivateDidReceiveInitializationSegment(62DF0002)
WPEWebProcess[2883]: SourceBuffer::sourceBufferPrivateDidReceiveInitializationSegment(62DF0002)
WPEWebProcess[2883]: SourceBuffer::seekToTime(62DF0001) {
    "value":130}
WPEWebProcess[2883]: SourceBuffer::seekToTime(62DF0002) {
    "value":130}

参考

Launching the Debugger