From 9ed2af69be43d889f59ae1ca262af40405c481c5 Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Mon, 25 May 2026 18:05:45 -0500
Subject: perf(mousetrap): cache built keymaps per profile

mouse-trap--build-keymap ran on every major-mode hook and rebuilt the whole keymap (~8 prefixes by ~30 events) from scratch each time, so rapid mode-switching paid that cost over and over. I moved the build into mouse-trap--build-keymap-1 and cache its result in mouse-trap--keymap-cache, keyed on the profile name plus its allowed-categories list. The same profile reuses the cached keymap, and editing a profile's categories changes the key so it rebuilds.

Sharing one keymap object across buffers is safe here: the map only binds disallowed events to ignore and is never mutated after it's built. Added mouse-trap--clear-keymap-cache to force a fresh build after editing profiles by hand.
---
 tests/test-mousetrap-mode--keymap-cache.el | 84 ++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 tests/test-mousetrap-mode--keymap-cache.el

(limited to 'tests')

diff --git a/tests/test-mousetrap-mode--keymap-cache.el b/tests/test-mousetrap-mode--keymap-cache.el
new file mode 100644
index 00000000..09cb5e5c
--- /dev/null
+++ b/tests/test-mousetrap-mode--keymap-cache.el
@@ -0,0 +1,84 @@
+;;; test-mousetrap-mode--keymap-cache.el --- Tests for keymap caching -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for the per-profile keymap cache in mouse-trap--build-keymap.
+;; Repeated builds for the same profile should reuse one keymap object;
+;; distinct profiles get distinct objects; clearing the cache forces a rebuild.
+
+;;; Code:
+
+(require 'ert)
+(require 'mousetrap-mode)
+
+;; Each test starts from a clean cache so results don't depend on order.
+(defun test-mousetrap--with-clear-cache (thunk)
+  "Run THUNK with the keymap cache cleared before and after."
+  (mouse-trap--clear-keymap-cache)
+  (unwind-protect (funcall thunk)
+    (mouse-trap--clear-keymap-cache)))
+
+;;; Cache-hit cases
+
+(ert-deftest test-mousetrap-mode--keymap-cache-same-profile-returns-same-object ()
+  "Normal: two builds for the same profile return the same keymap (eq)."
+  (test-mousetrap--with-clear-cache
+   (lambda ()
+     (let ((major-mode 'test-mode)
+           (mouse-trap-mode-profiles '((test-mode . disabled))))
+       (let ((first (mouse-trap--build-keymap))
+             (second (mouse-trap--build-keymap)))
+         (should (eq first second)))))))
+
+(ert-deftest test-mousetrap-mode--keymap-cache-different-profiles-differ ()
+  "Normal: distinct profiles return distinct keymap objects."
+  (test-mousetrap--with-clear-cache
+   (lambda ()
+     (let* ((mouse-trap-mode-profiles '((mode-a . disabled)
+                                        (mode-b . full)))
+            (map-a (let ((major-mode 'mode-a)) (mouse-trap--build-keymap)))
+            (map-b (let ((major-mode 'mode-b)) (mouse-trap--build-keymap))))
+       (should-not (eq map-a map-b))))))
+
+;;; Cache-clear case
+
+(ert-deftest test-mousetrap-mode--keymap-cache-clear-forces-fresh-object ()
+  "Boundary: after clearing the cache, a rebuild yields a fresh object."
+  (test-mousetrap--with-clear-cache
+   (lambda ()
+     (let ((major-mode 'test-mode)
+           (mouse-trap-mode-profiles '((test-mode . disabled))))
+       (let ((first (mouse-trap--build-keymap)))
+         (mouse-trap--clear-keymap-cache)
+         (let ((second (mouse-trap--build-keymap)))
+           (should-not (eq first second))))))))
+
+(ert-deftest test-mousetrap-mode--keymap-cache-edited-categories-rebuild ()
+  "Boundary: editing a profile's category list at runtime changes the key,
+forcing a rebuild rather than returning the stale cached keymap."
+  (test-mousetrap--with-clear-cache
+   (lambda ()
+     (let ((major-mode 'test-mode)
+           (mouse-trap-mode-profiles '((test-mode . tweakable))))
+       (let* ((mouse-trap-profiles '((tweakable . (scroll))))
+              (first (mouse-trap--build-keymap)))
+         (let* ((mouse-trap-profiles '((tweakable . (scroll primary-click))))
+                (second (mouse-trap--build-keymap)))
+           (should-not (eq first second))
+           ;; Behavior reflects the edited categories.
+           (should (eq (lookup-key second (kbd "<mouse-1>")) nil))))))))
+
+;;; Behavior-preservation sanity
+
+(ert-deftest test-mousetrap-mode--keymap-cache-preserves-ignore-binding ()
+  "Normal: a cached keymap still binds a disallowed event to `ignore'."
+  (test-mousetrap--with-clear-cache
+   (lambda ()
+     (let ((major-mode 'test-mode)
+           (mouse-trap-mode-profiles '((test-mode . disabled))))
+       ;; Build twice; the cached object must still block the event.
+       (mouse-trap--build-keymap)
+       (let ((map (mouse-trap--build-keymap)))
+         (should (eq (lookup-key map (kbd "<mouse-1>")) 'ignore)))))))
+
+(provide 'test-mousetrap-mode--keymap-cache)
+;;; test-mousetrap-mode--keymap-cache.el ends here
-- 
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