DN548272500

Subject: Re: win/winMain.c -- main() and WinMain() are mutually exclusive - DN [1]

Scott Redman <scott.redman@bigfoot.com> - 13 Nov 1999 - comp.lang.tcl

 You've stumbled across my double-secret Console-wish code...

 On Windows, you can write a Windows app with -subsystem:console
 that has a main(), which calls WinMain().  I've done this
 before, and it's especially useful knowledge when porting to
 Unix with MainWin.

 The code is intended to be used to build a Console-based
 version of wish that doesn't use the "Tk Console", but
 rather the Win32 console.  It solves a number of issues,
 but has the annoying side-effect of creating an extra
 Win32 Console window for Wish when it's launched from
 the Start menu or from a window shortcut.

 When you build with -subsystem:windows, Windows will disconnect
 your application from stdin/stdout/stderr if they are a Win32
 console.  Rather annoying, but if it's a File handle (or pretty
 much anything else), Windows won't disconnect.  This means
 that (starting with Tcl/Tk 8.1) you can pipe stdout from wish
 into a file.

 I've considered the possibility of having to versions of
 wish installed, one built with -subsystem:windows as it
 normally is, but called "wish-win.exe".  Shortcuts will
 hide the name, and file associations will use it.
 Then, install a version built with -subsystem:console
 and call it "wish.exe".  It works beautifully when you
 run "wish" from a console.  If anyone thinks this is a
 good idea, send email to the WinTcl mailing list
 (wintcl@scriptics.com).

 -- Scott

 David Gravereaux wrote:
 >
 > I was just nosing around the code and noticed something in the comments of
 > main():
 >
 >  * main --
 >  *
 >  *      Main entry point from the console.
 >
 > I don't think that's correct.  An executable can only have one entry-point.  Is
 > main() here to be used with an alternate link step (aka -subsystem:console) ??
 >
 > The only thing different between main() and WinMain() is setting a flag for
 > whether the console widget should be started or not later in Tk_Init().  It
 > might be a nice feature to have the tclsh style console when cranked-up from the
 > command prompt.  It could break scripts though (??)
 >
 > Just for the fun of it, I was trying methods to discover if a WinMain can detect
 > if it was started from the console, but no luck trapping it.
 >
 >   STARTUPINFO si;
 >   HANDLE StdOut;
 >
 >   si.cb = sizeof(STARTUPINFO);
 >   GetStartupInfo(&si);
 >   StdOut = GetStdHandle(STD_OUTPUT_HANDLE);
 >
 >   if (si.hStdOutput != StdOut) {
 >     // inherited handle isn't the default
 >   }
 >
 > That didn't work in a WinMain.  Nor did this:
 >
 >   CONSOLE_SCREEN_BUFFER_INFO csbi; /* used to get cursor position */
 >
 >   GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE), &csbi);
 >   if (csbi.dwCursorPosition.X | csbi.dwCursorPosition.Y) {
 >     // non-zero cursor position
 >   }
 >
 > Anyone know of any tricks to see if a -subsystem:windows app was started from an
 > interactive console prompt?
 >
 > --
 > * David Gravereaux *
 > Tomahawk Software Group