Re: Why does command prompt appear on Windows when starting a GUI app?

[Brian Dessent <brian at dessent dot net>]

Barry Andrews wrote:

>    I have a GUI application that is compiled with gcj on Windows.  When I double click the .exe file in Windows Explorer, a command window comes up behind the GUI. Is there any way to get rid of this? Any help is much appreciated!

On win32, when linking a binary there is a field called "subsystem"
which determines the kind of binary.  This is documented on MSDN:
<http://msdn.microsoft.com/library/en-us/vccore/html/_core_.2f.subsystem.asp>

Just about all normal apps will fall into the "console" or "windows"
categories, and the only real difference between the two is that a
console is created for the application by default for the former,
whereas the application must allocate the console itself (if if even
needs one) in the latter.

Thus you just need to provide "--subsystem windows" to the linker to set
this field.  If you are using a compiler driver to link (as you should
be) instead of calling ld directly then you'll probably have to specify
this as "-Wl,--subsystem,windows".  The specs file for your compiler may
have defined "-mwindows" as a shortcut for this; you can check using the
-dumpspecs flag.

It has been my observation that a lot of people seem to think that
"-mwindows" is somehow necessary for creating a windows binary, or that
if they use "-mconsole" they cannot have a GUI.  This is simply not true
at all -- all this flag does is tell the linker to set the subsystem
field in the binary to a value which tells the system whether to
allocate a console by default.  It says nothing about whether the
application can create graphical windows or anything else.  But it is
true that often times if an application does have a GUI then it's not
desirable to have that console window created, so -mwindows sees a lot
of use in those apps.

Brian