win32 console/window app

windows_console.c

// Sometimes there is a need to make an application that behaves like a GUI app when ran via 
// explorer, but like console application when ran from console. This file implements such
// an application. On start, it will try to attach to a parent console. If that failed,
// that means that we ran from explorer, and we may want to allocate a console for debugging
// purposes. If we get a console either by attaching to it or by creating it, we will redirect
// std handles.
// At program termination we need to send enter to stdin in order to let the parent console
// know that we're done. I'm not sure why we need to do this but if it's not done, the parent
// will wait indefinately for user input.

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <stdio.h>

#if defined(DEBUG_CONSOLE)
    const bool do_open_debug_console = true;
#else
    const bool do_open_debug_console = false;
#endif

static bool win32_setup_console() {
    if(!AttachConsole(ATTACH_PARENT_PROCESS)) {
        if(do_open_debug_console) {
            if(!AllocConsole()) {
                return false;
            }
        }
        else {
            return true;
        }
    }
    HANDLE hstdout = GetStdHandle(STD_OUTPUT_HANDLE);
    HANDLE hstderr = GetStdHandle(STD_ERROR_HANDLE);
    HANDLE hstdin = GetStdHandle(STD_INPUT_HANDLE);
    if(hstdout == INVALID_HANDLE_VALUE) {
        return false;
    }
    if(hstderr == INVALID_HANDLE_VALUE) {
        return false;
    }
    if(hstdin == INVALID_HANDLE_VALUE) {
        return false;
    }
    if(freopen("CONOUT$", "w", stdout) == NULL) {
        return false;
    }
    if(freopen("CONOUT$", "w", stderr) == NULL) {
        return false;
    }
    if(freopen("CONIN$", "r", stdin) == NULL) {
        return false;
    }
    setvbuf(stderr, NULL, _IONBF, 0);
    setvbuf(stdout, NULL, _IONBF, 0);
    return true;
}

static void win32_send_enter(void) {
    INPUT_RECORD in_buffer[2] =
    {
        {
            .EventType = KEY_EVENT,
            .Event.KeyEvent = {
                .bKeyDown = 1,
                .wVirtualKeyCode = VK_RETURN,
                .wVirtualScanCode = MapVirtualKeyA(VK_RETURN, MAPVK_VK_TO_VSC),
                .uChar.AsciiChar = MapVirtualKeyA(VK_RETURN, MAPVK_VK_TO_CHAR),
            },
        },
        {
            .EventType = KEY_EVENT,
            .Event.KeyEvent = {
                .bKeyDown = 0,
                .wVirtualKeyCode = VK_RETURN,
                .wVirtualScanCode = MapVirtualKeyA(VK_RETURN, MAPVK_VK_TO_VSC),
                .uChar.AsciiChar = MapVirtualKeyA(VK_RETURN, MAPVK_VK_TO_CHAR),
            },
        },
    };
    DWORD written;
    WriteConsoleInput(
        GetStdHandle(STD_INPUT_HANDLE),
        &in_buffer[0],
        2,
        &written
    );

}

int WINAPI wWinMain(HINSTANCE inst, HINSTANCE pinst, PWSTR cmdline, int show) {
    if(!win32_setup_console()) {
        MessageBoxA(NULL, "Unable to find or create console", NULL, MB_OK);
        ExitProcess(1);
    }
    printf("Hello, world!\n");
    win32_send_enter();
    return 0;
}