[Stellarium-pubdevel] console output

[Matthew G. <mat...@gm...>]

During the QT-ization process, I have been swapping out cerr diagnostic 
output to qWarning(), qDebug(), and qFatal() output as appropriate.

I think we should do this for all console output.  We can then write a 
message handler to do something useful with this output which is 
appropriate to the OS.  See qInstallMsgHandler in the QT docs for more 
information.

There are a few things I would like to get your ideas on:

1. What to do about messages which are to be printed to standard output 
(e.g. --version option output, text splash).  I think using cout is OK 
here, but welcome other ideas.

2.  I think it would be helpful to have an explicit statement of when to use 
each level of error message, and what this means for the user.  I propose:

- qDebug() output is aimed mostly at developers. This would include the 
normal loading diagnostic "Loading" messages.  

- qWarning() output is still aimed mostly at developers, but should indicate 
some unexpected condition which does not cause an immediate problem but may 
have user-visible consequences .  Example: unable to locate or load a 
planet or nebula texture.

- qFatal() is to notify the user that a serious problem has occurred and 
that Stellarium cannot (or probably cannot) continue to run.  fatal 
messages should be presented to the user before unexpected termination of 
the program even if the user cannot see conole output.  I think a dialog 
box is a suitable mechanism for this.  They are intrusive, but if all is 
well the user should never see one.

- qCritical() I don't see a reason to use this at present - qWarning() and 
qFatal() seem adequate to me.


3.  We have some problems with users pasting diagnostic output into bug 
reports (which I often request of them):

* On Windows the cmd window has too small a scroll buffer and we lose some 
output.  The cmd window settings confuse the heck out of many users who 
simple cannot figure out how to copy the text in the window.  Thirdly, the 
window vanishes if Stellarium crashes, meaning we cannot see output from 
the most important bugs (and persuading windows users to run from a cmd 
window and then to copy-paste is not always easy).  Lastly, many windows 
users hate this window appearing in the first place.  I think we should get 
rid of it.

* On other platforms (mostly OSX, but increasingly Linux too as the OS gains 
a less technical audience), I believe we lose some feedback because 
launching from the console is quite challenging for some people who are 
only used to running from some graphical launcher.


I would like to see two mechanisms for lowering the barrier to good bug 
reporting:

* Some sort of log file in the user data directory containing the output of 
the functions listed above.  The most important reason is for windows users 
to be able to get diagnostic output after a crash.

* An in-program way to see diagnostic output, and copy it to the clipboard - 
perhaps something like the tilde menu which ID software games have (aka. 
the "quake" console).


Let me know what you think.  My apologies for the long posting.


Matthew