diff -r 302971e8599b -r 9dd76cbd6c90 src/ascension/window.h
--- a/src/ascension/window.h	Wed Nov 01 20:09:49 2023 +0100
+++ b/src/ascension/window.h	Wed Nov 01 21:00:33 2023 +0100
@@ -30,7 +30,13 @@
 
 #include <SDL2/SDL.h>
 
-#include "core.h"
+#include "datatypes.h"
+
+#ifndef ASC_MAX_WINDOWS
+/** The maximum number of windows that can exist simultaneously. */
+#define ASC_MAX_WINDOWS 4
+#endif // ASC_MAX_WINDOWS
+
 
 #ifdef __cplusplus
 extern "C" {
@@ -71,10 +77,14 @@
 /**
  * Creates and initializes a new window and a corresponding OpenGL context.
  *
- * @param window the window structure
+ * The index specified must not be in use by another window already.
+ * The maximum number of windows is defined by #ASC_MAX_WINDOWS.
+ *
+ * @param index the index of the new window
  * @param settings the settings to be used for initialization
+ * @return a pointer to the window data or \c NULL if initialization failed
  */
-void asc_window_initialize(AscWindow* window, AscWindowSettings const* settings);
+AscWindow *asc_window_initialize(unsigned int index, AscWindowSettings const* settings);
 
 /**
  * Destroys the window and its OpenGL context.