http://yal.cc/gamemaker-windows-functions-for-gamemaker-studio/

WinDev.cpp

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

#define dllx extern "C" __declspec(dllexport)

dllx double delay(double ms) {
	Sleep((DWORD)ms);
	return 1;
}

static COLORREF get_colors[16];
dllx double get_color_win(double c) { // 
	CHOOSECOLOR cc;
	ZeroMemory(&cc, sizeof(cc));
	cc.lStructSize = sizeof(cc);
	cc.hwndOwner = GetActiveWindow();
	cc.lpCustColors = (LPDWORD)get_colors;
	cc.rgbResult = (int)c;
	cc.Flags = CC_FULLOPEN | CC_RGBINIT;
	if (ChooseColor(&cc) == TRUE) {
		return cc.rgbResult;
	} else return c;
}

dllx double file_copy_win(char* source, char* dest) {
	return CopyFile(source, dest, false) != 0;
}

dllx double window_set_caption_ext(double w, char* s) { //
	int ptr = w;
	SetWindowText((HWND)ptr, s);
	return ptr;
}

#define SHELL_SHOWCMD SW_SHOWNORMAL

// for completely mysterious reasons, this particular function
// always returns FILE_NOT_FOUND, even with "open" action hardcoded.
dllx double shell_open(char* file) {
	return (int)ShellExecute(NULL, NULL, file, NULL, NULL, SHELL_SHOWCMD);
}

dllx double shell_do(char* action, char* file) {
	return (int)ShellExecute(NULL, action, file, NULL, NULL, SHELL_SHOWCMD);
}

dllx double shell_do_at(char* action, char* file, char* directory) {
	return (int)ShellExecute(NULL, action, file, NULL, directory, SHELL_SHOWCMD);
}

dllx double shell_do_ext(char* action, char* file, char* params, char* directory) {
	return (int)ShellExecute(NULL, action, file, params, directory, SHELL_SHOWCMD);
}

dllx double shell_execute(char* file, char* params) {
	return (int)ShellExecute(NULL, NULL, file, params, NULL, SHELL_SHOWCMD);
}

dllx double shell_execute_at(char* file, char* params, char* directory) {
	return (int)ShellExecute(NULL, NULL, file, params, directory, SHELL_SHOWCMD);
}

dllx char* file_text_get(char* file) {
	FILE *f;
	char *r = NULL;
	long fl;
	fopen_s(&f, file, "r");
	if (f) {
		fseek(f, 0L, SEEK_END);
		fl = ftell(f);
		rewind(f);
		if (r = (char*)calloc(1, fl + 1)) {
			// if a file-sized string was allocated successfully.
			if (!fread(r, fl, 1, f)) {
				// if failed to read the contents, dealloc the string.
				free(r);
				r = NULL;
			}
		}
		fclose(f);
	}
	if (r == NULL) {
		// errors yield empty strings
		r = (char*)calloc(1, 1);
		r[0] = 0;
	}
	return r;
}

dllx double file_text_put(char* file, char* text) {
	FILE *f;
	fopen_s(&f, file, "w");
	int r = 0;
	if (f) {
		if (fputs(text, f)) {
			r = 1;
		}
		fclose(f);
	}
	return r;
}