Let yasl_app_desc describe its initial window

A new optional yasl_app_desc.window spec makes yasl_run() create that
toplevel and request its first frame before init(), which is now
optional too. If creation fails, yasl_run() closes the display and
returns an error without calling init().

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/include/yasl/app.h b/include/yasl/app.h
index f067d5b..79b2519 100644
--- a/include/yasl/app.h
+++ b/include/yasl/app.h
@@ -148,10 +148,16 @@ struct yasl_app_desc {
     enum yasl_backend backend;
     /** User data passed to all callbacks. */
     void *userdata;
+    /**
+     * Optional toplevel created before init(), with its first frame requested.
+     * Borrowed for the call; spec cbs and ud are ignored as for any runner window.
+     * yasl_run() returns an error without calling init() if creation fails.
+     */
+    const struct yasl_window_spec *window;
 
     /**
-     * Called once after display and event machinery initialization.
-     * Use this to create windows and initialize application resources.
+     * Optional; called once after display and event machinery initialization.
+     * Use this to create further windows and initialize application resources.
      * Return YASL_APP_CONTINUE or YASL_APP_QUIT.
      */
     enum yasl_app_result (*init)(void *ud, struct yasl_display *d);