Re: [Mingw-cross-env-list] Unneeded Qt dependency

[Nikos Chantziaras]

On 06/21/2011 08:41 AM, Nikos Chantziaras wrote:
> On 06/21/2011 08:10 AM, Nikos Chantziaras wrote:
> > I see that qt.mk lists "libiconv" as a dependency. This is not needed
> > for Windows. Thiago Macieira mentioned on:
> >
> > http://lists.qt.nokia.com/pipermail/qt-interest/2010-August/026692.html
> >
> > "libiconv is not used on Windows."
>
> Though without libiconv, it seems there are link errors anyway. So I'm
> puzzled at what's happening here. I'll ask about it on the Qt list.

OK, I now know what's going on.  And mingw-cross-env has a problem here. 
 Qt applications will fail silently in the current way Qt is built.  I 
was hit by this bug; a Windows user reported wrong text rendering in my 
app.  The issue is that the application needs to explicitly include the 
text codec plugins for them to work.  In the *.pro file:

  QTPLUGIN += qcncodecs qjpcodecs qtwcodecs qkrcodecs

And somewhere in the program sources:

  #include <QtPlugin>
  Q_IMPORT_PLUGIN(qcncodecs)
  Q_IMPORT_PLUGIN(qjpcodecs)
  Q_IMPORT_PLUGIN(qtwcodecs)
  Q_IMPORT_PLUGIN(qkrcodecs)

The problem here is that when building Qt without specifying the 
"-no-iconv" configure option, the application will build and appear to 
run fine without the need to include the plugins as shown above.  This 
is bad (*very* bad), because the application will be unable to convert 
any text using the QTextCodec classes.  For example, in my app I had 
something like this:

  QTextCodec* cp1252 = QTextCodec::codecForName("Windows-1252");
  // ...
  // Convert from 1252 to Unicode before printing on screen.
  QString str = cp1252->toUnicode(srcText);

The above compiles and runs fine, but it *does not* convert anything! 
It's a silent bug, and we all know how nasty those are (I wasted a lot 
of time trying to track down the bug.)

Short answer: mingw-cross-env should build Qt with "-no-iconv".  That 
way, the programmer will get linker errors when trying to build his 
application.  That way, he will know that he *must* include the text 
codec plugins.

I am attaching a patch with the needed modifications to qt.mk and the 
qt-test sample program.

qt-noiconv.patch
Description: Text document