Add cape-capf-with-predicate (See #9)

2 files changed, 11 insertions, 0 deletions

diff --git a/README.org b/README.org
index eef1a87..8ec09ab 100644
--- a/README.org
+++ b/README.org
@@ -120,3 +120,4 @@ achieve a similarly refreshing strategy.
 
 - ~cape-silent-capf~: Wrap a chatty Capf and silence it.
 - ~cape-capf-with-properties~: Add completion properties to a Capf.
+- ~cape-capf-with-predicate~: Add predicate to control if the Capf should activate.
diff --git a/cape.el b/cape.el
index db93c6d..e041254 100644
--- a/cape.el
+++ b/cape.el
@@ -682,6 +682,16 @@ The CMP argument determines how the new input is compared to the old input.
              ('substring (string-match-p (regexp-quote old-input) new-input))))))
 
 ;;;###autoload
+(defun cape-capf-with-predicate (capf predicate)
+  "Return a new CAPF which activates only when the PREDICATE is non-nil.
+The PREDICATE takes the completion beginning and end positions as arguments."
+  (lambda ()
+    (pcase (funcall capf)
+      ((and result `(,beg ,end ,_table . ,_plist))
+       (when (funcall predicate beg end)
+         result)))))
+
+;;;###autoload
 (defun cape-capf-with-properties (capf &rest properties)
   "Return a new CAPF with additional completion PROPERTIES.
 Completion properties include for example :exclusive, :annotation-function