22 files changed, 184 insertions, 34 deletions
diff --git a/README.org b/README.org
index 36f41cd..7185995 100644
--- a/README.org
+++ b/README.org
@@ -417,6 +417,73 @@ Other examples:
 (setq ef-themes-region '(intense no-extend neutral))
 #+end_src
 
+** Palette overrides
+:PROPERTIES:
+:CUSTOM_ID: h:4b923795-4b23-4345-81e5-d1c108a84b6a
+:END:
+#+cindex: Override color values and semantic color mappings
+
+[ Part of {{{development-version}}}. ]
+
+Each theme defines its own color palette as well as semantic color
+mappings.  The former is the set of color values such as what shade of
+blue to use.  The latter refers to associations between a color value
+and a syntactic construct, such as a =variable= for variables in
+programming modes or =heading-1= for level 1 headings in Org and
+others.
+
+The definition is stored in the variable =ef-NAME-palette=, where
+=NAME= is the specifier of the theme, such as ~ef-summer-palette~ for
+the ~ef-summer~ theme.  Overrides for those associations are specified
+in the variable =ef-NAME-palette-overrides=.
+
+All associations take the form of =(KEY VALUE)= pairs.  For example,
+the ~ef-summer-palette~ contains =(blue-warmer "#5250ef")=.  Semantic
+color mappings are the same, though the =VALUE= is one of the named
+colors of the theme.  For instance, =ef-summer-palette= maps the
+aforementioned =blue-warmer= to =variable= thus =(variable blue-warmer)=.
+
+The easiest way to learn about a theme's definition is to use the
+command ~describe-variable~ (bound to =C-h v= by default) and then
+search for the =ef-NAME-palette=.  The resulting Help buffer will look
+like this:
+
+#+begin_example
+ef-summer-palette is a variable defined in ‘ef-summer-theme.el’.
+
+Its value is shown below.
+
+The ‘ef-summer’ palette.
+
+  This variable may be risky if used as a file-local variable.
+
+Value:
+((bg-main "#fff2f3")
+ (fg-main "#4f4073")
+
+[... Shortened for the purposes of this manual.]
+#+end_example
+
+The user can study this information to identify the overrides they
+wish to make.  Then they can specify them and re-load the theme for
+changes to take effect.  Sample of how to override a color value and a
+semantic mapping:
+
+#+begin_src emacs-lisp
+(setq ef-summer-palette-overrides
+      '((blue-warmer "#5230ff") ; original value is #5250ef
+        (variable cyan))) ; original value is blue-warmer
+#+end_src
+
+The overrides can contain as many associations as the user needs.
+
+Changes to color values are reflected in the preview of the theme's
+palette ([[#h:8dd67bf5-879e-46e5-b277-5bac141f53d1][Preview theme colors]]).  They are shown at the top of the
+buffer.  In the above example, the first instance of =blue-warmer= is
+the override and the second is the original one.
+
+Contact me if you need further help with this.
+
 * Loading a theme
 :PROPERTIES:
 :CUSTOM_ID: h:75d74aea-d17f-497f-a3b8-f0bf4c372de0
@@ -550,6 +617,9 @@ which reflects the given choice, like =ef-summer-preview-colors= for the
 The command ~ef-themes-preview-colors-current~ skips the minibuffer
 selection process and just produces a preview for the current Ef theme.
 
+Overrides to color values are reflected in the buffers produced by the
+aforementioned commands ([[#h:4b923795-4b23-4345-81e5-d1c108a84b6a][Palette overrides]]).
+
 * Use colors from the active Ef theme
 :PROPERTIES:
 :CUSTOM_ID: h:5b74bd9e-e7f2-46b3-af2e-7c45b2e69245
diff --git a/ef-autumn-theme.el b/ef-autumn-theme.el
index 4ed9ed3..7f237de 100644
--- a/ef-autumn-theme.el
+++ b/ef-autumn-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow))
     "The `ef-autumn' palette.")
 
-  (ef-themes-theme ef-autumn ef-autumn-palette)
+  (defvar ef-autumn-palette-overrides nil
+    "Overrides for `ef-autumn-palette'.")
+
+  (ef-themes-theme ef-autumn ef-autumn-palette ef-autumn-palette-overrides)
 
   (provide-theme 'ef-autumn))
 
diff --git a/ef-bio-theme.el b/ef-bio-theme.el
index 57b3316..f8b5b71 100644
--- a/ef-bio-theme.el
+++ b/ef-bio-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 magenta))
     "The `ef-bio' palette.")
 
-  (ef-themes-theme ef-bio ef-bio-palette)
+  (defvar ef-bio-palette-overrides nil
+    "Overrides for `ef-bio-palette'.")
+
+  (ef-themes-theme ef-bio ef-bio-palette ef-bio-palette-overrides)
 
   (provide-theme 'ef-bio))
 
diff --git a/ef-cherie-theme.el b/ef-cherie-theme.el
index c21b161..6b21b6b 100644
--- a/ef-cherie-theme.el
+++ b/ef-cherie-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 magenta-cooler))
     "The `ef-cherie' palette.")
 
-  (ef-themes-theme ef-cherie ef-cherie-palette)
+  (defvar ef-cherie-palette-overrides nil
+    "Overrides for `ef-cherie-palette'.")
+
+  (ef-themes-theme ef-cherie ef-cherie-palette ef-cherie-palette-overrides)
 
   (provide-theme 'ef-cherie))
 
diff --git a/ef-cyprus-theme.el b/ef-cyprus-theme.el
index d245e02..e4065dc 100644
--- a/ef-cyprus-theme.el
+++ b/ef-cyprus-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 red))
     "The `ef-cyprus' palette.")
 
-  (ef-themes-theme ef-cyprus ef-cyprus-palette)
+  (defvar ef-cyprus-palette-overrides nil
+    "Overrides for `ef-cyprus-palette'.")
+
+  (ef-themes-theme ef-cyprus ef-cyprus-palette ef-cyprus-palette-overrides)
 
   (provide-theme 'ef-cyprus))
 
diff --git a/ef-dark-theme.el b/ef-dark-theme.el
index 5b8069a..126815f 100644
--- a/ef-dark-theme.el
+++ b/ef-dark-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow))
     "The `ef-dark' palette.")
 
-  (ef-themes-theme ef-dark ef-dark-palette)
+  (defvar ef-dark-palette-overrides nil
+    "Overrides for `ef-dark-palette'.")
+
+  (ef-themes-theme ef-dark ef-dark-palette ef-dark-palette-overrides)
 
   (provide-theme 'ef-dark))
 
diff --git a/ef-day-theme.el b/ef-day-theme.el
index 65f036c..e46ae82 100644
--- a/ef-day-theme.el
+++ b/ef-day-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 green-cooler))
     "The `ef-day' palette.")
 
-  (ef-themes-theme ef-day ef-day-palette)
+  (defvar ef-day-palette-overrides nil
+    "Overrides for `ef-day-palette'.")
+
+  (ef-themes-theme ef-day ef-day-palette ef-day-palette-overrides)
 
   (provide-theme 'ef-day))
 
diff --git a/ef-deuteranopia-dark-theme.el b/ef-deuteranopia-dark-theme.el
index 9bee52f..5b1a352 100644
--- a/ef-deuteranopia-dark-theme.el
+++ b/ef-deuteranopia-dark-theme.el
@@ -205,7 +205,10 @@
       (rainbow-8 magenta-faint))
     "The `ef-deuteranopia-dark' palette.")
 
-  (ef-themes-theme ef-deuteranopia-dark ef-deuteranopia-dark-palette)
+  (defvar ef-deuteranopia-dark-palette-overrides nil
+    "Overrides for `ef-deuteranopia-dark-palette'.")
+
+  (ef-themes-theme ef-deuteranopia-dark ef-deuteranopia-dark-palette ef-deuteranopia-dark-palette-overrides)
 
   (provide-theme 'ef-deuteranopia-dark))
 
diff --git a/ef-deuteranopia-light-theme.el b/ef-deuteranopia-light-theme.el
index 57b299a..acc1123 100644
--- a/ef-deuteranopia-light-theme.el
+++ b/ef-deuteranopia-light-theme.el
@@ -205,7 +205,10 @@
       (rainbow-8 cyan))
     "The `ef-deuteranopia-light' palette.")
 
-  (ef-themes-theme ef-deuteranopia-light ef-deuteranopia-light-palette)
+  (defvar ef-deuteranopia-light-palette-overrides nil
+    "Overrides for `ef-deuteranopia-light-palette'.")
+
+  (ef-themes-theme ef-deuteranopia-light ef-deuteranopia-light-palette ef-deuteranopia-light-palette-overrides)
 
   (provide-theme 'ef-deuteranopia-light))
 
diff --git a/ef-duo-dark-theme.el b/ef-duo-dark-theme.el
index 22c476f..056005f 100644
--- a/ef-duo-dark-theme.el
+++ b/ef-duo-dark-theme.el
@@ -205,7 +205,10 @@
       (rainbow-8 green-cooler))
     "The `ef-duo-dark' palette.")
 
-  (ef-themes-theme ef-duo-dark ef-duo-dark-palette)
+  (defvar ef-duo-dark-palette-overrides nil
+    "Overrides for `ef-duo-dark-palette'.")
+
+  (ef-themes-theme ef-duo-dark ef-duo-dark-palette ef-duo-dark-palette-overrides)
 
   (provide-theme 'ef-duo-dark))
 
diff --git a/ef-duo-light-theme.el b/ef-duo-light-theme.el
index 0ad7383..d83f1ce 100644
--- a/ef-duo-light-theme.el
+++ b/ef-duo-light-theme.el
@@ -206,7 +206,10 @@
       (rainbow-8 green-cooler))
     "The `ef-duo-light' palette.")
 
-  (ef-themes-theme ef-duo-light ef-duo-light-palette)
+  (defvar ef-duo-light-palette-overrides nil
+    "Overrides for `ef-duo-light-palette'.")
+
+  (ef-themes-theme ef-duo-light ef-duo-light-palette ef-duo-light-palette-overrides)
 
   (provide-theme 'ef-duo-light))
 
diff --git a/ef-frost-theme.el b/ef-frost-theme.el
index 780dcf3..3411b12 100644
--- a/ef-frost-theme.el
+++ b/ef-frost-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 cyan-warmer))
     "The `ef-frost' palette.")
 
-  (ef-themes-theme ef-frost ef-frost-palette)
+  (defvar ef-frost-palette-overrides nil
+    "Overrides for `ef-frost-palette'.")
+
+  (ef-themes-theme ef-frost ef-frost-palette ef-frost-palette-overrides)
 
   (provide-theme 'ef-frost))
 
diff --git a/ef-light-theme.el b/ef-light-theme.el
index 28c6aac..06f1d9c 100644
--- a/ef-light-theme.el
+++ b/ef-light-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow))
     "The `ef-light' palette.")
 
-  (ef-themes-theme ef-light ef-light-palette)
+  (defvar ef-light-palette-overrides nil
+    "Overrides for `ef-light-palette'.")
+
+  (ef-themes-theme ef-light ef-light-palette ef-light-palette-overrides)
 
   (provide-theme 'ef-light))
 
diff --git a/ef-night-theme.el b/ef-night-theme.el
index 8b5c572..71df32e 100644
--- a/ef-night-theme.el
+++ b/ef-night-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 green-warmer))
     "The `ef-night' palette.")
 
-  (ef-themes-theme ef-night ef-night-palette)
+  (defvar ef-night-palette-overrides nil
+    "Overrides for `ef-night-palette'.")
+
+  (ef-themes-theme ef-night ef-night-palette ef-night-palette-overrides)
 
   (provide-theme 'ef-night))
 
diff --git a/ef-spring-theme.el b/ef-spring-theme.el
index 3b1fdc6..f2ab6e5 100644
--- a/ef-spring-theme.el
+++ b/ef-spring-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow-cooler))
     "The `ef-spring' palette.")
 
-  (ef-themes-theme ef-spring ef-spring-palette)
+  (defvar ef-spring-palette-overrides nil
+    "Overrides for `ef-spring-palette'.")
+
+  (ef-themes-theme ef-spring ef-spring-palette ef-spring-palette-overrides)
 
   (provide-theme 'ef-spring))
 
diff --git a/ef-summer-theme.el b/ef-summer-theme.el
index ccf5af3..d970dec 100644
--- a/ef-summer-theme.el
+++ b/ef-summer-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow-cooler))
     "The `ef-summer' palette.")
 
-  (ef-themes-theme ef-summer ef-summer-palette)
+  (defvar ef-summer-palette-overrides nil
+    "Overrides for `ef-summer-palette'.")
+
+  (ef-themes-theme ef-summer ef-summer-palette ef-summer-palette-overrides)
 
   (provide-theme 'ef-summer))
 
diff --git a/ef-themes.el b/ef-themes.el
index f2ce782..58f857b 100644
--- a/ef-themes.el
+++ b/ef-themes.el
@@ -415,15 +415,32 @@ foreground that is used with any of the intense backgrounds."
   "Return first enabled Ef theme."
   (car (ef-themes--list-enabled-themes)))
 
-(defun ef-themes--palette (theme)
-  "Return THEME palette as a symbol."
-  (when theme
-    (intern (format "%s-palette" theme))))
-
-(defun ef-themes--current-theme-palette ()
-  "Return palette of active Ef theme, else produce `user-error'."
-  (if-let* ((palette (ef-themes--palette (ef-themes--current-theme))))
-      (symbol-value palette)
+(defun ef-themes--palette-symbol (theme &optional overrides)
+  "Return THEME palette as a symbol.
+With optional OVERRIDES, return THEME palette overrides as a
+symbol."
+  (when-let ((suffix (cond
+                      ((and theme overrides)
+                       "palette-overrides")
+                      (theme
+                       "palette"))))
+    (intern (format "%s-%s" theme suffix))))
+
+(defun ef-themes--palette-value (theme &optional overrides)
+  "Return palette value of THEME with optional OVERRIDES."
+  (let ((base-value (symbol-value (ef-themes--palette-symbol theme))))
+    (if overrides
+        (append (symbol-value (ef-themes--palette-symbol theme :overrides)) base-value)
+      base-value)))
+
+(defun ef-themes--current-theme-palette (&optional overrides)
+  "Return palette value of active Ef theme, else produce `user-error'.
+With optional OVERRIDES return palette value plus whatever
+overrides."
+  (if-let ((theme (ef-themes--current-theme)))
+      (if overrides
+          (ef-themes--palette-value theme :overrides)
+        (ef-themes--palette-value theme))
     (user-error "No enabled Ef theme could be found")))
 
 (defun ef-themes--choose-subset ()
@@ -552,7 +569,7 @@ symbol."
 Routine for `ef-themes-preview-colors'."
   (let ((palette (seq-remove (lambda (cell)
                                (symbolp (cadr cell)))
-                             (symbol-value (ef-themes--palette theme))))
+                             (ef-themes--palette-value theme :overrides)))
         (current-buffer buffer)
         (current-theme theme))
     (with-help-window buffer
@@ -1953,17 +1970,20 @@ Helper function for `ef-themes-preview-colors'."
 ;;;; Instantiate an Ef theme
 
 ;;;###autoload
-(defmacro ef-themes-theme (name palette)
+(defmacro ef-themes-theme (name palette &optional overrides)
   "Bind NAME's color PALETTE around face specs and variables.
 Face specifications are passed to `custom-theme-set-faces'.
 While variables are handled by `custom-theme-set-variables'.
 Those are stored in `ef-themes-faces' and
-`ef-themes-custom-variables' respectively."
+`ef-themes-custom-variables' respectively.
+
+Optional OVERRIDES are appended to PALETTE, overriding
+corresponding entries."
   (declare (indent 0))
   (let ((sym (gensym))
         (colors (mapcar #'car (symbol-value palette))))
     `(let* ((c '((class color) (min-colors 256)))
-            (,sym ,palette)
+            (,sym (append ,overrides ,palette))
             ,@(mapcar (lambda (color)
                         (list color
                               `(let* ((value (car (alist-get ',color ,sym))))
@@ -1987,7 +2007,7 @@ Those are stored in `ef-themes-faces' and
          ;; inside a function.
          (colors (mapcar #'car (ef-themes--current-theme-palette))))
     `(let* ((c '((class color) (min-colors 256)))
-            (,sym (ef-themes--current-theme-palette))
+            (,sym (ef-themes--current-theme-palette :overrides))
             ,@(mapcar (lambda (color)
                         (list color
                               `(let* ((value (car (alist-get ',color ,sym))))
diff --git a/ef-trio-dark-theme.el b/ef-trio-dark-theme.el
index 177b33e..805f601 100644
--- a/ef-trio-dark-theme.el
+++ b/ef-trio-dark-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow-cooler))
     "The `ef-trio-dark' palette.")
 
-  (ef-themes-theme ef-trio-dark ef-trio-dark-palette)
+  (defvar ef-trio-dark-palette-overrides nil
+    "Overrides for `ef-trio-dark-palette'.")
+
+  (ef-themes-theme ef-trio-dark ef-trio-dark-palette ef-trio-dark-palette-overrides)
 
   (provide-theme 'ef-trio-dark))
 
diff --git a/ef-trio-light-theme.el b/ef-trio-light-theme.el
index 05bbd72..5c8f437 100644
--- a/ef-trio-light-theme.el
+++ b/ef-trio-light-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 yellow-cooler))
     "The `ef-trio-light' palette.")
 
-  (ef-themes-theme ef-trio-light ef-trio-light-palette)
+  (defvar ef-trio-light-palette-overrides nil
+    "Overrides for `ef-trio-light-palette'.")
+
+  (ef-themes-theme ef-trio-light ef-trio-light-palette ef-trio-light-palette-overrides)
 
   (provide-theme 'ef-trio-light))
 
diff --git a/ef-tritanopia-dark-theme.el b/ef-tritanopia-dark-theme.el
index b9c8e6f..88576c1 100644
--- a/ef-tritanopia-dark-theme.el
+++ b/ef-tritanopia-dark-theme.el
@@ -205,7 +205,10 @@
       (rainbow-8 red-faint))
     "The `ef-tritanopia-dark' palette.")
 
-  (ef-themes-theme ef-tritanopia-dark ef-tritanopia-dark-palette)
+  (defvar ef-tritanopia-dark-palette-overrides nil
+    "Overrides for `ef-tritanopia-dark-palette'.")
+
+  (ef-themes-theme ef-tritanopia-dark ef-tritanopia-dark-palette ef-tritanopia-dark-palette-overrides)
 
   (provide-theme 'ef-tritanopia-dark))
 
diff --git a/ef-tritanopia-light-theme.el b/ef-tritanopia-light-theme.el
index fb408a4..126c181 100644
--- a/ef-tritanopia-light-theme.el
+++ b/ef-tritanopia-light-theme.el
@@ -205,7 +205,10 @@
       (rainbow-8 red-faint))
     "The `ef-tritanopia-light' palette.")
 
-  (ef-themes-theme ef-tritanopia-light ef-tritanopia-light-palette)
+  (defvar ef-tritanopia-light-palette-overrides nil
+    "Overrides for `ef-tritanopia-light-palette'.")
+
+  (ef-themes-theme ef-tritanopia-light ef-tritanopia-light-palette ef-tritanopia-light-palette-overrides)
 
   (provide-theme 'ef-tritanopia-light))
 
diff --git a/ef-winter-theme.el b/ef-winter-theme.el
index f17a342..b361cfe 100644
--- a/ef-winter-theme.el
+++ b/ef-winter-theme.el
@@ -202,7 +202,10 @@
       (rainbow-8 cyan-warmer))
     "The `ef-winter' palette.")
 
-  (ef-themes-theme ef-winter ef-winter-palette)
+  (defvar ef-winter-palette-overrides nil
+    "Overrides for `ef-winter-palette'.")
+
+  (ef-themes-theme ef-winter ef-winter-palette ef-winter-palette-overrides)
 
   (provide-theme 'ef-winter))