Silence Warnings: QFont::setPixelSize

[Brandon Hilkert]

I'm getting these on the output of my spec request specs...

QFont::setPixelSize: Pixel size <= 0 (0)

Is there a way to silence or resolve this?

Thanks,

Brandon

[Joe Ferris]

Hey Brandon,

I don't think anybody's found a way to turn off warnings in general. If you do find a way, please let me know or submit a pull request.

Thanks,

-Joe

[Brandon Hilkert]

Joe,

Thanks for the speedy reply. No problem. Just wanted to make sure I wasn't missing something obvious.

best,

Brandon

[Mark Gibbins]

Have you tried defining 'QT_NO_DEBUG_OUTPUT' and 'QT_NO_WARNING_OUTPUT'?

via PhantomJS: https://github.com/ariya/phantomjs/blob/775c2ad2aff6849ab024445bad4db307d8c61fc1/src/phantomjs.pro#L7

[Joe Ferris]

I haven't tried that yet; good find. Care to put together a pull request?

[Mark Gibbins]

I was going to send one over, but I was in two minds about tests. Would you need one for this?

[Joe Ferris]

Having one would be better, and we already have the ability to capture STDOUT from the server, so I don't think it will be too bad as long as it's easy to reproduce the issue in a test.

[Mark Gibbins]

Okay, I've done some more digging around and it seems the debug messages may come out even if you supply those flags when building capybara-webkit if you're using the pre-built binary from homebrew, or simply a debug version. The homebrew formula builds with the configure flag "-with-debug-and-release", making it pop out the warnings no matter what. The solution is to use a release build of Qt, or just build it yourself. With a release build, the flags work and capybara-webkit stays silent. I'm finishing the test(s) now and should have a pull request for you soon.

[Joe Ferris]

Hey Mark,

Thanks again for looking into this. I'm looking forward to the pull request.

-Joe

[Mark Gibbins]

Hi Joe,

Turns out this is a bit more complex than I laid out above. It seems that even with those flags and a fresh release build of Qt, it still prints the debug messages. It has something to do with the strange (at least to me!) way that the QDebug lib works. Apparently it doesn't really matter what flags you use, it just blurts out these messages. So in the end I had to actually root out the exact message being printed (I discovered it in th QtGui lib as part of text rendering), rewrite all the debug messages in that lib to check for debug flags and then recompile it.

I'm not sure it's much of a problem for Rails developers as it sends the messages to STDOUT, but I was testing a command line client and it was failing the tests. Besides, It's just plain annoying!

If you need more details on the exact edits let me know, as it might fall out of the scope of the project now.

- Mark

[Jan Maurits Faber]

I get the same annoying warnings. Since this bug seems to have been in Qt for years, perhaps there is a way to simply this particular message from the stderr stream? I haven't been successful in getting rid of them yet.

[Joe Ferris]

I think you could set up some kind of a filter list using qInstallMsgHandler: http://qt-project.org/doc/qt-4.8/qtglobal.html#qInstallMsgHandler

[Mark Gibbins]

FWIW, the actual edits to completely silence the warnings are very minimal (a conditional define in one function). What about just overriding the method that prints this message?

[Joe Ferris]

Which function are you talking about? Are you suggesting that we override something from Qt?

[Amin Ariana]

There's an open issue on this on GitHub: https://github.com/thoughtbot/capybara-webkit/issues/485 ... sadly, it references this thread without any new information. This is the only warning I get in my Capbara Webkit integration tests.

QFont::setPixelSize: Pixel size <= 0 (0)

There's a very old QT bug report for this, from 2 years ago as well:

http://qt.gitorious.org/qt/qt/merge_requests/933

Wonder what others did to suppress this warning successfully in Rails / RSpec? 

[Joe Ferris]

You can suppress a number of warnings by installing a version of Qt that doesn't have DEBUG compiled in. Downloading the official versions (http://qt-project.org/downloads) is one way to do this.

We've also discussed a new feature that would allow people to filter messages by a pattern. I haven't had time to work on it yet, but if anybody's interested in contributing, please email me directly and I'll explain what would be involved in writing a pull request for it.

-Joe

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[Amin Ariana]

Thanks Joe -

FYI, fwiw I uninstalled my brew version of QT and installed the non-debug official 4.8 version. A ran my Capybara Webkit tests and I still do get the "QFont::setPixelSize: Pixel size <= 0 (0)" warning.

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[Joe Ferris]

If you install a new version of Qt, you'll also need to recompile capybara-webkit by uninstalling and reinstalling.

You can figure out which version of Qt capybara-webkit is using with this command on OS X:

    otool -L $(bundle show capybara-webkit)/bin/webkit_server

I believe you can use `ldd` instead of `otool -L` on Linux.

-Joe

[Amin Ariana]

Thanks for the quick follow up Joe.

I uninstalled and reinstalled the gem, still get the same warning. Here is the output of the command you suggested after the reinstall (and I double checked that in between, the webkit_server directory was empty) :

QtWebKit.framework/Versions/4/QtWebKit (compatibility version 4.9.0, current version 4.9.3)

QtGui.framework/Versions/4/QtGui (compatibility version 4.8.0, current version 4.8.4)

QtCore.framework/Versions/4/QtCore (compatibility version 4.8.0, current version 4.8.4)

QtNetwork.framework/Versions/4/QtNetwork (compatibility version 4.8.0, current version 4.8.4)

/usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current version 52.0.0)

/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 1105.0.0)

/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 159.1.0)

Here's the qmake / QT version:

qmake -v

QMake version 2.01a

Using Qt version 4.8.4 in /Library/Frameworks

This is on Mac OSX Lion if that matters. Also I do have QT 5 installed in parallel to 4.8, but doesn't look like it's been used. I'm slightly surprised by the version that QtWebKit is listing (4.9).