A proper (let's hope) fix for the sluggishness problem

1 files changed, 25 insertions, 15 deletions

diff --git a/elisp/geiser-syntax.el b/elisp/geiser-syntax.el
index f5d8cfa..52f0d8f 100644
--- a/elisp/geiser-syntax.el
+++ b/elisp/geiser-syntax.el
@@ -228,26 +228,36 @@
 (defsubst geiser-syntax--pair-length (p)
   (if (cdr (last p)) (1+ (safe-length p)) (length p)))
 
+(defun geiser-syntax--shallow-form (boundary)
+  (when (looking-at-p "\\s(")
+    (save-excursion
+      (forward-char)
+      (let ((elems))
+        (ignore-errors
+          (while (< (point) boundary)
+            (skip-syntax-forward "-<>")
+            (when (<= (point) boundary)
+              (forward-sexp)
+              (let ((s (symbol-at-point)))
+                (when (not (eq s '.)) (push (symbol-at-point) elems))))))
+        (nreverse elems)))))
+
 (defun geiser-syntax--scan-sexps (&optional begin)
-  (let* ((start (point))
-         (go-on t)
-         (fst (geiser-syntax--symbol-at-point))
+  (let* ((fst (geiser-syntax--symbol-at-point))
          (smth (or fst (not (looking-at-p "[\s \s)\s>\s<\n]"))))
          (path (and fst `((,fst 0)))))
     (save-excursion
-      (geiser-syntax--skip-comment/string)
-      (while (and go-on (not (zerop (geiser-syntax--nesting-level))))
-        (let ((boundary (1+ (point))))
+      (while (not (zerop (geiser-syntax--nesting-level)))
+        (let ((boundary (point)))
+          (geiser-syntax--skip-comment/string)
           (backward-up-list)
-          (when (setq go-on (< (- start (point)) 2000))
-            (let ((form
-                   (nth-value 0 (geiser-syntax--form-after-point boundary))))
-              (when (and (listp form) (car form) (symbolp (car form)))
-                (let* ((len (geiser-syntax--pair-length form))
-                       (pos (if smth (1- len) (progn (setq smth t) len)))
-                       (prev (and (> pos 1) (nth (1- pos) form)))
-                       (prev (and (keywordp prev) (list prev))))
-                  (push `(,(car form) ,pos ,@prev) path))))))))
+          (let ((form (geiser-syntax--shallow-form boundary)))
+            (when (and (listp form) (car form) (symbolp (car form)))
+              (let* ((len (geiser-syntax--pair-length form))
+                     (pos (if smth (1- len) (progn (setq smth t) len)))
+                     (prev (and (> pos 1) (nth (1- pos) form)))
+                     (prev (and (keywordp prev) (list prev))))
+                (push `(,(car form) ,pos ,@prev) path)))))))
     (nreverse path)))
 
 (defsubst geiser-syntax--binding-form-p (bfs sbfs f)