feat(compose): open compose and conflict buffers in a configurable side window

The compose buffers (edit-description, add-comment) and the smerge conflict buffer popped wherever display-buffer happened to put them. Now they open in a side window, defaulting to the bottom at 30% of the frame, with two defcustoms to control it: pearl-compose-window-side (bottom / top / left / right) and pearl-compose-window-size (a fraction of the frame, or an absolute line/column count). pearl--compose-display-action builds the display-buffer-in-side-window action and both pop sites pass it through pop-to-buffer, so Pearl always applies the side window over any display-buffer-alist entry for these buffers.

2 files changed, 53 insertions, 2 deletions

diff --git a/pearl.el b/pearl.el
index 3ade6dc..f08f636 100644
--- a/pearl.el
+++ b/pearl.el
@@ -146,6 +146,34 @@ With the default nil, `pearl-surface-buffer' shows the buffer via
   :type 'boolean
   :group 'pearl)
 
+(defcustom pearl-compose-window-side 'bottom
+  "Side of the frame Pearl's compose and conflict buffers open from.
+One of `bottom', `top', `left', or `right'.  Pearl always applies this side
+window when popping a compose buffer, overriding any `display-buffer-alist'
+entry for those buffers."
+  :type '(choice (const bottom) (const top) (const left) (const right))
+  :group 'pearl)
+
+(defcustom pearl-compose-window-size 0.3
+  "Size of Pearl's compose and conflict side window.
+A float below 1 is a fraction of the frame (0.3 = 30%); an integer is an
+absolute size in lines (for `bottom'/`top') or columns (for `left'/`right').
+Paired with `pearl-compose-window-side'."
+  :type 'number
+  :group 'pearl)
+
+(defun pearl--compose-display-action ()
+  "Return the `display-buffer' action for a compose or conflict buffer.
+A side window on `pearl-compose-window-side', sized by
+`pearl-compose-window-size' -- `window-width' for the left/right sides,
+`window-height' for top/bottom."
+  (cons '(display-buffer-in-side-window)
+        (list (cons 'side pearl-compose-window-side)
+              (cons (if (memq pearl-compose-window-side '(left right))
+                        'window-width
+                      'window-height)
+                    pearl-compose-window-size))))
+
 (defun pearl--surface-buffer (buffer)
   "Bring BUFFER to a window after a command updated it, unless already shown.
 No-op when `pearl-surface-buffer' is nil, BUFFER is dead, or BUFFER is already
@@ -2136,7 +2164,7 @@ sibling of `pearl--resolve-conflict-in-smerge'."
       (local-set-key (kbd "C-c C-c") #'pearl--compose-submit)
       (local-set-key (kbd "C-c C-k") #'pearl--compose-abort)
       (goto-char (point-max)))
-    (pop-to-buffer buf)
+    (pop-to-buffer buf (pearl--compose-display-action))
     buf))
 
 (defvar-local pearl--conflict-on-finish nil
@@ -2171,7 +2199,7 @@ given, is a thunk run on abort so the save engine can report the outcome."
       (setq-local header-line-format
                   (substitute-command-keys
                    "Resolve the conflict, then \\[pearl--conflict-commit] to push, \\[pearl--conflict-abort] to abort")))
-    (pop-to-buffer buf)))
+    (pop-to-buffer buf (pearl--compose-display-action))))
 
 (defun pearl--conflict-commit ()
   "Finish the current pearl conflict buffer, pushing the reconciled text.
diff --git a/tests/test-pearl-compose.el b/tests/test-pearl-compose.el
index 7029297..3e62c09 100644
--- a/tests/test-pearl-compose.el
+++ b/tests/test-pearl-compose.el
@@ -149,5 +149,28 @@ Binds `captured' to the value the on-finish receives (or `:none').  Stubs
         (goto-char (point-min))
         (should (re-search-forward "Edited description" nil t))))))
 
+;;; compose-window display action
+
+(ert-deftest test-pearl-compose-display-action-defaults-to-bottom-fraction ()
+  "By default the compose window opens at the bottom, sized to 30% of the frame."
+  (should (equal '((display-buffer-in-side-window) (side . bottom) (window-height . 0.3))
+                 (pearl--compose-display-action))))
+
+(ert-deftest test-pearl-compose-display-action-honors-side-and-size ()
+  "The side and size defcustoms drive the action; left/right size the width,
+top/bottom the height, and the size passes through as float or integer."
+  (let ((pearl-compose-window-side 'right)
+        (pearl-compose-window-size 40))
+    (should (equal '((display-buffer-in-side-window) (side . right) (window-width . 40))
+                   (pearl--compose-display-action))))
+  (let ((pearl-compose-window-side 'top)
+        (pearl-compose-window-size 0.25))
+    (should (equal '((display-buffer-in-side-window) (side . top) (window-height . 0.25))
+                   (pearl--compose-display-action))))
+  (let ((pearl-compose-window-side 'left)
+        (pearl-compose-window-size 0.2))
+    (should (equal '((display-buffer-in-side-window) (side . left) (window-width . 0.2))
+                   (pearl--compose-display-action)))))
+
 (provide 'test-pearl-compose)
 ;;; test-pearl-compose.el ends here