Added main.c on the Unix backend to the rewrite.

new/unix/main.c

@@ -0,0 +1,42 @@
+// 6 april 2015
+#include "uipriv_unix.h"
+
+uiInitOptions options;
+
+const char *uiInit(uiInitOptions *o)
+{
+	GError *err = NULL;
+	const char *msg;
+
+	options = *o;
+	if (gtk_init_with_args(NULL, NULL, NULL, NULL, NULL, &err) == FALSE) {
+		msg = g_strdup(err->message);
+		g_error_free(err);
+		return msg;
+	}
+	return NULL;
+}
+
+void uiFreeInitError(const char *err)
+{
+	g_free((gpointer) err);
+}
+
+void uiMain(void)
+{
+	gtk_main();
+}
+
+// gtk_main_quit() may run immediately, or it may wait for other pending events; "it depends" (thanks mclasen in irc.gimp.net/#gtk+)
+// PostQuitMessage() on Windows always waits, so we must do so too
+// we'll do it by using an idle callback
+static gboolean quit(gpointer data)
+{
+	gtk_main_quit();
+	return FALSE;
+}
+
+void uiQuit(void)
+{
+	gdk_threads_add_idle(quit, NULL);
+}