[elpa] externals/fontaine 748d4ed863 1/4: Define the fontaine-toggle-preset command

[ELPA Syncer]

branch: externals/fontaine
commit 748d4ed863b31d6a9ad9a048171ea783b8628197
Author: Protesilaos Stavrou <info@protesilaos.com>
Commit: Protesilaos Stavrou <info@protesilaos.com>

    Define the fontaine-toggle-preset command
---
 README.org  |  7 +++++++
 fontaine.el | 47 ++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/README.org b/README.org
index ff464a2f8e..286cea522b 100644
--- a/README.org
+++ b/README.org
@@ -203,6 +203,13 @@ the =.emacs.d= directory).  Saving is done by the function
 function ~fontaine-restore-latest-preset~ (such as by adding it to their
 init file).
 
+#+findex: fontaine-toggle-preset
+The command ~fontaine-toggle-preset~ can toggle between the last two
+valid presets, as set by ~fontaine-set-preset~. If it cannot find two
+different presets, then it prompts using minibuffer completion. As a
+final step, it calls the ~fontaine-set-preset-hook~. [ The
+~fontaine-toggle-preset~ is part of {{{development-version}}}. ]
+
 For users of the =no-littering= package, ~fontaine-latest-state-file~ is
 not stored in their =.emacs.d=, but in a standard directory instead:
 https://github.com/emacscollective/no-littering.
diff --git a/fontaine.el b/fontaine.el
index 6cf6b62392..81ad188041 100644
--- a/fontaine.el
+++ b/fontaine.el
@@ -402,12 +402,24 @@ If FRAME is nil, apply the effect to all frames."
                symbol))
            fontaine-presets)))
 
-(defun fontaine--set-fonts-prompt ()
-  "Prompt for font set (used by `fontaine-set-fonts')."
+(defun fontaine--get-preset-symbols ()
+  "Return list of the `car' of each element in `fontain-presets'."
+  (delq nil
+        (mapcar
+         (lambda (element)
+           (when-let ((first (car element))
+                      (_ (not (eq first t))))
+             first))
+         fontaine-presets)))
+
+(defun fontaine--set-fonts-prompt (&optional prompt)
+  "Prompt for font set (used by `fontaine-set-fonts').
+If optional PROMPT string, use it for the prompt, else use one that asks
+for a preset among `fontaine-presets'."
   (let* ((def (nth 1 fontaine--font-display-hist))
-         (prompt (if def
-                     (format "Apply font configurations from PRESET [%s]: " 
def)
-                   "Apply font configurations from PRESET: ")))
+         (prompt (if prompt
+                     (format-prompt prompt nil)
+                   (format-prompt "Apply font configurations from PRESET" 
def))))
     (intern
      (completing-read
       prompt
@@ -474,6 +486,31 @@ which this function ignores"
       (fontaine-set-preset current)
     (user-error "The `fontaine-current-preset' is not among 
`fontaine-presets'")))
 
+(defun fontaine--get-first-non-current-preset (history)
+  "Return the first element of HISTORY which is not `fontaine-current-preset'.
+Only consider elements that are still part of the `fontaine-presets',
+per `fontaine--get-preset-symbols'."
+  (catch 'first
+    (dolist (element history)
+      (when (stringp element)
+        (setq element (intern element)))
+      (when (and (not (eq element fontaine-current-preset))
+                 (member element (fontaine--get-preset-symbols)))
+        (throw 'first element)))))
+
+;;;###autoload
+(defun fontaine-toggle-preset ()
+  "Toggle between the last two known Fontaine presets.
+These are the presets that were set with `fontaine-set-preset'.  If
+there are no two selected presets, then prompt the user to set a preset.
+
+As a final step, call the `fontaine-set-preset-hook'."
+  (interactive)
+  (fontaine-set-preset
+   (if-let ((previous (fontaine--get-first-non-current-preset 
fontaine--font-display-hist)))
+       previous
+     (fontaine--set-fonts-prompt "No previous preset to toggle; select 
PRESET"))))
+
 ;;;; Store and restore preset
 
 (defvar fontaine--preset-history '()