Fix invisible default-styled text on Linux framebuffer TTY

lisp/ghostel.el

@@ -284,8 +284,7 @@ or backing scale factor."
 shrinking entirely so CJK and other fallback glyphs render at
 natural size, potentially making rows slightly taller and cells slightly wider."
   :type '(float 0.0 1.0)
-  :local t
-  :group 'ghostel)
+  :local t)
 
 (defcustom ghostel-kitty-graphics-storage-limit (* 320 1024 1024)  ; 320 MiB
   "Kitty graphics image storage cap, in bytes, per terminal.
@@ -5360,18 +5359,21 @@ the rest of Emacs (e.g. a dark terminal inside a light Emacs)."
 
 (defun ghostel--face-hex-color (face attr)
   "Extract hex color string from FACE's ATTR (:foreground or :background).
-Falls back to \"#000000\" if the color cannot be resolved."
+Falls back to white (for :foreground) or black (for :background)."
   (or (let ((color (face-attribute face attr nil 'default)))
-        (when (and (stringp color) (not (string= color "unspecified")))
+        (when (and (stringp color)
+                   (not (member color '("unspecified"
+                                        "unspecified-fg"
+                                        "unspecified-bg"))))
           (let ((rgb (color-values color)))
             (if rgb
                 (apply #'format "#%02x%02x%02x"
                        (mapcar (lambda (c) (ash c -8)) rgb))
-              ;; Batch mode: color-values returns nil without a display.
-              ;; If the color is already "#RRGGBB", use it directly.
+              ;; Batch mode / TTY: color-values returns nil without a
+              ;; display.  If the color is already "#RRGGBB", use it.
               (and (string-prefix-p "#" color) (= (length color) 7)
                    color)))))
-      "#000000"))
+      (if (eq attr :foreground) "#ffffff" "#000000")))
 
 (defun ghostel--apply-palette (term)
   "Apply colors from `ghostel-color-palette' faces and default fg/bg to TERM."

test/ghostel-render-test.el

@@ -311,6 +311,24 @@ through without cross-call munging.)"
                  (string-prefix-p "#" color)
                  (= (length color) 7)))))
 
+(ert-deftest ghostel-test-face-hex-color-tty-unspecified ()
+  "TTY sentinel colors must not collapse fg and bg to the same hex (#297).
+On a Linux framebuffer the `default' face reports \"unspecified-fg\" and
+\"unspecified-bg\".  If `ghostel--face-hex-color' returned the same
+fallback for both, the buffer default face was remapped black-on-black
+and typed text was invisible."
+  (cl-letf (((symbol-function 'face-attribute)
+             (lambda (_face attr &optional _frame _inherit)
+               (pcase attr
+                 (:foreground "unspecified-fg")
+                 (:background "unspecified-bg")
+                 (_ 'unspecified)))))
+    (let ((fg (ghostel--face-hex-color 'ghostel-default :foreground))
+          (bg (ghostel--face-hex-color 'ghostel-default :background)))
+      (should (string-match-p "\\`#[0-9a-fA-F]\\{6\\}\\'" fg))
+      (should (string-match-p "\\`#[0-9a-fA-F]\\{6\\}\\'" bg))
+      (should-not (string= fg bg)))))
+
 (ert-deftest ghostel-test-hyperlinks ()
   "Test hyperlink keymap and helpers."
   :tags '(native)