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copied!<p>There are several approaches for applications that need to choose whether to act as console or GUI applications, depending on context, on Windows:</p> <ol> <li>Have two separate applications, and have one conditionally start the other.</li> <li>A variant of the above strategy, have two applications, one called 'app.com' (i.e. just rename a console EXE with COM extension) and the other called 'app.exe', so that command-line invocations will find app.com first. Because of ancient DOS compatibility, .COM executables are found before .EXEs. (This in configurable in Windows; see the PATHEXT environment variable.)</li> <li>The rxvt/Cygwin technique, which is one I haven't really seen documented anywhere else.</li> </ol> <p>Let me go into a little bit of detail about how rxvt on Cygwin works. Rxvt is a terminal emulator that normally runs on the X Window system. Because of the limitations of the Win32 console, Cygwin packages it as a more fully-featured console, with support for things like lots of lines of history, dynamic resizing, per-instance configurable fonts and colour themes, non-application-freezing mouse select and copy, etc. In order to run natively on Windows, rxvt shipped with Cygwin includes a tiny X11 wrapper library for Win32. Rxvt on Windows is actually a console application for compatibility reasons with existing native Win32 executables, but most of the time you never see the console; you just see the rxvt terminal emulator window itself.</p> <p>The way it works is specifically implemented in <code>rxvt/W11/wrap/wrap.c</code> in the rxvt source tree, in the function called <code>hideConsole()</code>. Basically, it opens up its console (with a <code>CreateFile("CONOUT$" ...)</code>), and checks to see if the cursor position is at (0,0) (using <code>GetConsoleScreenBufferInfo()</code> on the console handle).</p> <p>If it is, then it infers that it has been started as a standalone application, rather than from a console parent application, and thus it knows the OS has created a dedicated Win32 console for the process. It proceeds to hide this console window, but it has to find it first. It uses <code>SetConsoleTitle</code> to set the console window's caption to a unique value based on the name of the application and the current thread ID. It then uses <code>FindWindow</code> to find this window's handle (periodically <code>Sleep</code>ing for a few ms if necessary for the title to change, because the console windows are actually controlled by a different process entirely in Windows). When it eventually finds the window handle, it hides it with <code>ShowWindowAsync</code>, passing in <code>SW_HIDE</code>.</p> <p>Using this approach, you can write an application that:</p> <ul> <li>if started from a console parent, it can continue to use this console</li> <li>if started as an application, it can optionally choose whether or not to hide the console</li> </ul> <p>The only downside is a very brief flash of a console window at application startup.</p>

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