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To: cygwin AT cygwin DOT com
Subject: RE: Ctrl-Z fails to suspend Windows programs
From: John Cooper <John DOT Cooper AT eu DOT citrix DOT com>
Date: Tue, 15 Jun 2004 16:11:41 +0100
Message-ID: <87ekogc0uq.fsf@eu.citrix.com>
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 > The point is that it's not about cygwin-vs-windoze apps.  It's about
 > apps-that-use-console-stdin-and-stdout vs. apps-that-display-a-gui; those
 > that show a gui could usefully be detached, but those that read their input
 > from stdin will break if the shell detaches them.


Yes, you're right, the old "native" zsh option was specifically to do with GUI
apps rather than "Windows" apps per se - here's the doc to for enabling the
option (it was off by default):

  winntwaitforguiapps: When set, makes the shell wait for win32 GUI apps to
  terminate instead of spawning them asynchronously.

 > I don't think there's a reliable enough mechanism by which a shell could
 > detect one case from the other.

Below is the code it used to determine if a program is a GUI program or not. I
don't know how well it works under all conditions; however it did work fine for
me.

Even if not perfectly reliable, could something like this be added but disabled
by default?  I for one would find it useful.

    --- John


/*
How To Determine Whether an Application is Console or GUI     [win32sdk]
ID: Q90493     CREATED: 15-OCT-1992   MODIFIED: 16-DEC-1996
*/
#include <winnt.h>
#define xmalloc(s) HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,(s))
#define xfree(p) HeapFree(GetProcessHeap(),0,(p))
#define XFER_BUFFER_SIZE 2048

int is_gui(char *exename) {

	HANDLE hImage;

	DWORD  bytes;
	DWORD  SectionOffset;
	DWORD  CoffHeaderOffset;
	DWORD  MoreDosHeader[16];

	ULONG  ntSignature;

	IMAGE_DOS_HEADER      image_dos_header;
	IMAGE_FILE_HEADER     image_file_header;
	IMAGE_OPTIONAL_HEADER image_optional_header;


	hImage = CreateFile(exename, GENERIC_READ, FILE_SHARE_READ, NULL,
			OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

	if (INVALID_HANDLE_VALUE == hImage) {
		return 0;
	}

	/*
	 *  Read the MS-DOS image header.
	 */
	if (!ReadFile(hImage, &image_dos_header, sizeof(IMAGE_DOS_HEADER),
			&bytes,NULL)){
		CloseHandle(hImage);
		return 0;
	}

	if (IMAGE_DOS_SIGNATURE != image_dos_header.e_magic) {
		CloseHandle(hImage);
		return 0;
	}

	/*
	 *  Read more MS-DOS header.       */
	if (!ReadFile(hImage, MoreDosHeader, sizeof(MoreDosHeader),
			&bytes,NULL)){
		CloseHandle(hImage);
		return 0;
	}

	/*
	 *  Get actual COFF header.
	 */
	CoffHeaderOffset = SetFilePointer(hImage, image_dos_header.e_lfanew,
			NULL,FILE_BEGIN);

	if (CoffHeaderOffset == (DWORD) -1){
		CloseHandle(hImage);
		return 0;
	}

	CoffHeaderOffset += sizeof(ULONG);

	if (!ReadFile (hImage, &ntSignature, sizeof(ULONG),
			&bytes,NULL)){
		CloseHandle(hImage);
		return 0;
	}

	if (IMAGE_NT_SIGNATURE != ntSignature) {
		CloseHandle(hImage);
		return 0;
	}

	SectionOffset = CoffHeaderOffset + IMAGE_SIZEOF_FILE_HEADER +
		IMAGE_SIZEOF_NT_OPTIONAL_HEADER;

	if (!ReadFile(hImage, &image_file_header, IMAGE_SIZEOF_FILE_HEADER,
			&bytes, NULL)){
		CloseHandle(hImage);
		return 0;
	}

	/*
	 *  Read optional header.
	 */
	if (!ReadFile(hImage, &image_optional_header, 
			IMAGE_SIZEOF_NT_OPTIONAL_HEADER,&bytes,NULL)) {
		CloseHandle(hImage);
		return 0;
	}

	CloseHandle(hImage);

	if (image_optional_header.Subsystem ==IMAGE_SUBSYSTEM_WINDOWS_GUI)
		return 1;
	return 0;
}
int is_9x_gui(char *prog) {
	
	char *progpath;
	DWORD dwret;
	char *pathbuf;
	char *pext;
	
	pathbuf=xmalloc(MAX_PATH);

	progpath=xmalloc(MAX_PATH<<1);

	if (GetEnvironmentVariable("PATH",pathbuf,MAX_PATH) ==0) {
		goto failed;
	}
	
	pathbuf[MAX_PATH]=0;

	dwret = SearchPath(pathbuf,prog,".EXE",MAX_PATH<<1,progpath,&pext);

	if ( (dwret == 0) || (dwret > (MAX_PATH<<1) ) )
		goto failed;
	
	dprintf("progpath is %s\n",progpath);
	dwret = is_gui(progpath);

	xfree(pathbuf);
	xfree(progpath);

	return dwret;

failed:
	xfree(pathbuf);
	xfree(progpath);
	return 0;


}
 


    --- John

-----Original Message-----
From: Dave Korn [mailto:dk AT artimi DOT com] 
Sent: 15 June 2004 15:40
To: 'John Cooper'; cygwin AT cygwin DOT com
Subject: RE: Ctrl-Z fails to suspend Windows programs

> -----Original Message-----
> From: cygwin-owner On Behalf Of John Cooper
> Sent: 15 June 2004 15:05
> To: cygwin
> Subject: RE: Ctrl-Z fails to suspend Windows programs
> 
> The old native (non-cygwin) port of zsh would somehow detect if it was 
> about to exec a Windows app, and run it as a background process, thus 
> returning a zsh prompt immediately.  Could something like this be 
> added to cygwin bash/zsh?

  AFAICS the ability is already there.  Just enter "windows_app.exe &" at a bash shell.

> This was very useful.  With the cygwin zsh, I often find myself 
> invoking a Windows app and not being able to get back to the shell 
> window without first terminating the Windows app.

Well, the same goes if you run a cygwin app: you don't get the prompt back until it exits.
 
The point is that it's not about cygwin-vs-windoze apps.  It's about
apps-that-use-console-stdin-and-stdout vs. apps-that-display-a-gui; those that
show a gui could usefully be detached, but those that read their input from
stdin will break if the shell detaches them.  I don't think there's a reliable
enough mechanism by which a shell could detect one case from the other.

Try starting insight (gui version of gdb) from the bash prompt.  You also won't
get a shell back until it exits.


    cheers, 
      DaveK
--
Can't think of a witty .sigline today....


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