Size side windows by body width and add test

Author: tninja

ai-code-backends-infra.el

@@ -62,7 +62,7 @@ Can be either `vterm' or `eat'."
   :group 'ai-code-backends-infra)
 
 (defcustom ai-code-backends-infra-window-width 90
-  "Width of the side window when opened on left or right."
+  "Body width of the side window when opened on left or right."
   :type 'integer
   :group 'ai-code-backends-infra)
 
@@ -521,7 +521,8 @@ MULTILINE-INPUT-SEQUENCE configures `S-<return>' and `C-<return>' when non-nil."
                         (side . ,side)
                         (slot . 0)
                         ,@(when (memq side '(left right))
-                            `((window-width . ,ai-code-backends-infra-window-width)))
+                            `((window-width
+                               . ,#'ai-code-backends-infra--fit-side-window-body-width)))
                         ,@(when (memq side '(top bottom))
                             `((window-height . ,ai-code-backends-infra-window-height)))
                         (window-parameters . ((no-delete-other-windows . t)))))))
@@ -532,6 +533,13 @@ MULTILINE-INPUT-SEQUENCE configures `S-<return>' and `C-<return>' when non-nil."
       (select-window window))
     window))
 
+(defun ai-code-backends-infra--fit-side-window-body-width (window)
+  "Resize WINDOW so its body width matches `ai-code-backends-infra-window-width'."
+  (let ((delta (- ai-code-backends-infra-window-width
+                  (window-body-width window))))
+    (unless (zerop delta)
+      (window-resize window delta t))))
+
 ;;; Session Helpers
 
 (defun ai-code-backends-infra--session-working-directory ()

test/test_ai-code-backends-infra.el

@@ -215,6 +215,30 @@
           (advice-remove handler #'ai-code-backends-infra--terminal-reflow-filter))
         (fmakunbound handler)))))
 
+(ert-deftest test-ai-code-backends-infra-display-buffer-in-side-window-uses-body-width ()
+  "Horizontal side windows should size to the configured body width."
+  (with-temp-buffer
+    (let ((ai-code-backends-infra-use-side-window t)
+          (ai-code-backends-infra-window-side 'right)
+          (ai-code-backends-infra-window-width 100)
+          (ai-code-backends-infra-focus-on-open nil)
+          captured-entry
+          resize-call)
+      (rename-buffer " *ai-code-side-width*" t)
+      (cl-letf (((symbol-function 'display-buffer)
+                 (lambda (_buffer &optional _action)
+                   (setq captured-entry (car display-buffer-alist))
+                   'fake-window))
+                ((symbol-function 'window-body-width)
+                 (lambda (_window) 96))
+                ((symbol-function 'window-resize)
+                 (lambda (window delta horizontal)
+                   (setq resize-call (list window delta horizontal)))))
+        (ai-code-backends-infra--display-buffer-in-side-window (current-buffer))
+        (should (functionp (cdr (assq 'window-width captured-entry))))
+        (funcall (cdr (assq 'window-width captured-entry)) 'fake-window)
+        (should (equal resize-call '(fake-window 4 t)))))))
+
 (ert-deftest test-ai-code-backends-infra-sync-terminal-cursor-vterm-copy-mode ()
   "Show an Emacs cursor in vterm copy mode and restore terminal cursor on exit."
   (with-temp-buffer