From 47d7e31800e72c626b783065269fb79d4694fcf1 Mon Sep 17 00:00:00 2001
From: Daniel Borchmann <daniel@algebra20.de>
Date: Mon, 13 Feb 2023 13:22:51 +0100
Subject: [PATCH] Let display-buffer handle window placement for shells

This provides the same functionality, but makes it more configurable.
---
 init.el                | 11 ++++++++++-
 site-lisp/db-eshell.el | 19 ++++++++-----------
 site-lisp/db-utils.el  |  8 +++-----
 3 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/init.el b/init.el
index 52b8333..8b0370b 100644
--- a/init.el
+++ b/init.el
@@ -623,11 +623,20 @@
                            (side . right)
                            (slot . 0)
                            (window-width . 0.33)))
+            ;; Inspired by masteringemacs
             (add-to-list 'display-buffer-alist
                          '("^\\*Help\\*"
                            (display-buffer-reuse-window
                             display-buffer-pop-up-window)
-                           (inhibit-same-window . t)))))
+                           (inhibit-same-window . t)))
+            ;; Inspired by masteringemacs
+            (add-to-list 'display-buffer-alist
+                         '("^\\*e?shell\\*"
+                           display-buffer-in-direction
+                           (direction . bottom)
+                           (window . root)
+                           (window-height . 0.33)
+                           (dedicated . t)))))
 
 (use-package winner
   :commands (winner-mode winner-undo winner-redo))
diff --git a/site-lisp/db-eshell.el b/site-lisp/db-eshell.el
index e068598..fb47775 100644
--- a/site-lisp/db-eshell.el
+++ b/site-lisp/db-eshell.el
@@ -23,10 +23,8 @@
 ;; Various
 
 (defun db/run-or-hide-eshell (arg)
-  "Opens an eshell buffer if not already in one, and otherwise
-  returns to where we have been before."
-  ;; idea to split the current window is from
-  ;; http://howardism.org/Technical/Emacs/eshell-fun.html
+  "Opens an eshell buffer if not already in one.
+Otherwise moves the cursor to the window where we have been before."
   (interactive "P")
   (if (derived-mode-p 'eshell-mode)
       ;; bury buffer; reopen with current working directory if arg is given
@@ -35,17 +33,16 @@
         (and arg (db/run-or-hide-eshell arg)))
     (if-let ((eshell-window (db/find-window-by-buffer-mode 'eshell-mode)))
         (select-window eshell-window)
-      ;; open eshell
-      (let* ((current-dir (expand-file-name default-directory))
-             (height      (/ (frame-text-lines) 3)))
-        (select-window (split-window (frame-root-window) (- height) 'below))
-        (eshell 1)
+      ;; No running eshell found, open new one.
+      (let* ((current-dir (expand-file-name default-directory)))
+        (--if-let (display-buffer (eshell 1))
+            (select-window it)
+          (error "Could not start eshell (`display-buffer' returned nil)"))
         (when arg
           (end-of-line)
           (eshell-kill-input)
           (insert (format "cd '%s'" current-dir))
-          (eshell-send-input))))
-    (set-window-dedicated-p (selected-window) t)))
+          (eshell-send-input))))))
 
 (defun eshell-clear-buffer ()
   "Clear terminal."
diff --git a/site-lisp/db-utils.el b/site-lisp/db-utils.el
index 4b0cc86..4774200 100644
--- a/site-lisp/db-utils.el
+++ b/site-lisp/db-utils.el
@@ -74,11 +74,9 @@ If already in `*ansi-term*' buffer, bury it."
   (cl-flet ((change-to-shell ()
               (if-let ((shell-window (db/find-window-by-buffer-mode 'shell-mode)))
                   (select-window shell-window)
-                ;; open shell in buffer with height of ⅓ of current window
-                (let ((height (/ (frame-text-lines) 3)))
-                  (select-window (split-window (frame-root-window) (- height) 'below))
-                  (shell)))
-              (set-window-dedicated-p (selected-window) t)))
+                (--if-let (display-buffer (shell))
+                    (select-window it)
+                  (error "Could not start shell (`display-buffer' returned nil)")))))
     (if (not arg)
         ;; toggle shell window
         (if (not (derived-mode-p 'shell-mode))