Optimize reactive text property updates: only update relevant buffers

1. When using setq-local, only update the current buffer
2. When using setq, update all buffers that have the text property

Co-authored-by: Kinneyzhang <38454496+Kinneyzhang@users.noreply.github.com>

tp-tests.el

@@ -2680,5 +2680,69 @@ Returns list of (START END VALUE) intervals."
       (ignore-errors (makunbound 'tp-test-init-name))
       (ignore-errors (makunbound 'tp-test-init-other)))))
 
+(ert-deftest tp-test-setq-local-only-updates-current-buffer ()
+  "Test that setq-local only updates text properties in the current buffer."
+  (let ((buf1 nil)
+        (buf2 nil))
+    (unwind-protect
+        (progn
+          ;; Define a reactive layer
+          (tp-define-layer test-multi-buf-layer
+            :props (face (:foreground $tp-test-multi-color)))
+          ;; Create first buffer with layer applied
+          (setq buf1 (generate-new-buffer " *test-buf1*"))
+          (with-current-buffer buf1
+            (insert "Hello World")
+            (tp-set 1 6 'test-multi-buf-layer))
+          ;; Create second buffer with layer applied
+          (setq buf2 (generate-new-buffer " *test-buf2*"))
+          (with-current-buffer buf2
+            (insert "Hello World")
+            (tp-set 1 6 'test-multi-buf-layer))
+          ;; Use setq-local in buf1
+          (with-current-buffer buf1
+            (setq-local tp-test-multi-color "red"))
+          ;; buf1 should be updated
+          (with-current-buffer buf1
+            (should (equal (plist-get (get-text-property 1 'face) :foreground) "red")))
+          ;; buf2 should NOT be updated (still nil)
+          (with-current-buffer buf2
+            (should (equal (plist-get (get-text-property 1 'face) :foreground) nil))))
+      ;; Cleanup
+      (when (buffer-live-p buf1) (kill-buffer buf1))
+      (when (buffer-live-p buf2) (kill-buffer buf2))
+      (ignore-errors (makunbound 'tp-test-multi-color)))))
+
+(ert-deftest tp-test-setq-updates-all-buffers-with-property ()
+  "Test that setq updates text properties in all buffers that have the property."
+  (let ((buf1 nil)
+        (buf2 nil))
+    (unwind-protect
+        (progn
+          ;; Define a reactive layer
+          (tp-define-layer test-global-layer
+            :props (face (:foreground $tp-test-global-color)))
+          ;; Create first buffer with layer applied
+          (setq buf1 (generate-new-buffer " *test-buf1*"))
+          (with-current-buffer buf1
+            (insert "Hello World")
+            (tp-set 1 6 'test-global-layer))
+          ;; Create second buffer with layer applied
+          (setq buf2 (generate-new-buffer " *test-buf2*"))
+          (with-current-buffer buf2
+            (insert "Hello World")
+            (tp-set 1 6 'test-global-layer))
+          ;; Use global setq
+          (setq tp-test-global-color "blue")
+          ;; Both buffers should be updated
+          (with-current-buffer buf1
+            (should (equal (plist-get (get-text-property 1 'face) :foreground) "blue")))
+          (with-current-buffer buf2
+            (should (equal (plist-get (get-text-property 1 'face) :foreground) "blue"))))
+      ;; Cleanup
+      (when (buffer-live-p buf1) (kill-buffer buf1))
+      (when (buffer-live-p buf2) (kill-buffer buf2))
+      (ignore-errors (makunbound 'tp-test-global-color)))))
+
 (provide 'tp-ert-tests)
 ;;; tp-ert-tests.el ends here

tp.el

@@ -206,11 +206,14 @@ Only the reactive portions of the properties are stored for each variable."
   (tp--unregister-layer-computed layer-name)
   (tp--unregister-layer-data layer-name))
 
-(defun tp--reactive-variable-watcher (symbol newval operation _where)
+(defun tp--reactive-variable-watcher (symbol newval operation where)
   "Watcher function called when a reactive variable changes.
 SYMBOL is the variable that changed.
 NEWVAL is the new value being set.
 OPERATION is the type of operation (set, let, unlet, makunbound, defvaralias).
+WHERE indicates where the variable was set:
+  - nil for global `setq' or `set'
+  - a buffer for `setq-local'
 Updates all layers that depend on this variable.
 
 Only 'set' operations trigger updates because:
@@ -243,8 +246,10 @@ Only 'set' operations trigger updates because:
                     (cl-loop for (key val) on resolved-props by #'cddr
                              do (setq current-props (plist-put current-props key val)))
                     (tp--set-layer-props layer-name current-props))))))
-          ;; Update all text regions with this layer
+          ;; Update text regions with this layer
-          (tp--update-layer-regions layer-name))))))
+          ;; If WHERE is a buffer (setq-local), only update that buffer
+          ;; If WHERE is nil (setq), update all buffers that have the text property
+          (tp--update-layer-regions layer-name where))))))
 
 (defun tp--invoke-layer-watchers (layer-name symbol newval oldval)
   "Invoke all registered watcher callbacks for LAYER-NAME watching SYMBOL.
@@ -401,12 +406,25 @@ If a variable is not bound, define it with the initial value (nil if not specifi
       (unless (boundp var-sym)
         (set var-sym initial-val)))))
 
-(defun tp--update-layer-regions (layer-name)
+(defun tp--update-layer-regions (layer-name &optional where)
-  "Update all text regions that have LAYER-NAME applied.
+  "Update text regions that have LAYER-NAME applied.
-Re-applies the layer properties using tp-search-map and tp-add."
+Re-applies the layer properties using tp-search-map and tp-add.
+
+WHERE specifies which buffers to update:
+  - If WHERE is a buffer, only update that buffer (setq-local case).
+  - If WHERE is nil, update all buffers that have the text property (setq case)."
   (let ((props (tp-layer-props layer-name)))
     (when props
-      ;; Update in all buffers
+      (if (and where (bufferp where) (buffer-live-p where))
+          ;; setq-local case: only update the specific buffer
+          (with-current-buffer where
+            (save-excursion
+              (tp-search-map
+               (lambda (_text start end)
+                 (tp-add start end props)
+                 nil)
+               'tp-name layer-name)))
+        ;; setq case: update all buffers that have the text property
         (dolist (buf (buffer-list))
           (when (buffer-live-p buf)
             (with-current-buffer buf
@@ -419,7 +437,7 @@ Re-applies the layer properties using tp-search-map and tp-add."
                    (tp-add start end props)
                    ;; Return nil to skip text replacement
                    nil)
-               'tp-name layer-name))))))))
+                 'tp-name layer-name)))))))))
 
 (defun tp-reactive-reset ()
   "Reset all reactive text property watchers and dependencies."