Add input queue with delayed processing.

This avoids spamming `update-source' when the input is updated too fast (< input-delay).

Author: Ambrevar

prompter.lisp

@@ -25,6 +25,21 @@
       :accessor nil
       :reader input
       :documentation "User input.")
+     (input-queue
+      (lpara.queue:make-queue)
+      :type lpara.queue:queue
+      :export nil
+      :documentation "All user inputs.
+See `input-delay'.")
+     (input-delay
+      0.05
+      :type float
+      :documentation "When input is changed, time after which the source is updated.
+This is useful to avoid updating the sources")
+     (input-reader
+      nil
+      :export nil
+      :documentation "The Lparallel `future' that reads the various inputs during `input-delay'.")
 
      (prompt
       ""
@@ -199,14 +214,32 @@ Only if the PROMPTER current source has `actions-on-current-suggestion-enabled-p
   (:documentation "Set the action to be run on the newly selected suggestion.
 See also `run-action-on-current-suggestion'."))
 
+(defun drain-queue (queue)
+  "Drain and return last element of the `lparallel.queue:queue'."
+  (labels ((pop (last-value)
+             (multiple-value-bind (element hit?)
+                 (lparallel.queue:try-pop-queue queue)
+               (if hit?
+                   (pop element)
+                   last-value))))
+    (pop nil)))
+
 (export-always 'input)
 (defmethod (setf input) (text (prompter prompter))
-  "Update PROMPTER sources and return TEXT."
-  (let ((old-input (slot-value prompter 'input)))
-    (unless (string= old-input text)
-      (setf (slot-value prompter 'input) text)
-      (update-sources prompter text)
-      (first-suggestion prompter)))
+  "Update PROMPTER sources and return TEXT.
+This is non-blocking: the source update is done in parallel."
+  (when (or (null (input-reader prompter))
+            (lpara:fulfilledp (input-reader prompter)))
+    (setf (input-reader prompter)
+          (lparallel:future
+            (sleep (input-delay prompter))
+            (let ((input (drain-queue (input-queue prompter))))
+              (let ((old-input (slot-value prompter 'input)))
+                (unless (string= old-input text)
+                  (setf (slot-value prompter 'input) text)
+                  (update-sources prompter text)
+                  (first-suggestion prompter)))))))
+  (lpara.queue:push-queue input (input-queue prompter))
   text)
 
 (export-always 'destroy)