(while-no-input): New macro.

diff --git a/lisp/subr.el b/lisp/subr.el
index 3bdef5988ce376a3aa3c3a5cfe50735ed402a619..84129908fc7751076fda1fe922260a2e2ce03c76 100644 (file)
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1862,6 +1862,19 @@ is allowed once again."
         ,@body)
      (quit (setq quit-flag t) nil)))
 
+(defmacro while-no-input (&rest body)
+  "Execute BODY only as long as there's no pending input.
+If input arrives, that ends the execution of BODY,
+and `while-no-input' returns nil.  If BODY finishes,
+`while-no-input' returns whatever value BODY produced."
+  (declare (debug t) (indent 0))
+  (let ((catch-sym (make-symbol "input")))
+    `(with-local-quit
+       (catch ',catch-sym
+        (let ((throw-on-input ',catch-sym))
+          (when (sit-for 0 0 t)
+            ,@body))))))
+
 (defmacro combine-after-change-calls (&rest body)
   "Execute BODY, but don't call the after-change functions till the end.
 If BODY makes changes in the buffer, they are recorded