fix(design): clamp the gauge once so needle and readout agree

The needle angle clamped to 0-100 while the readout rendered the raw value, so a gauge fed 150 pinned the needle at +60 degrees under a "150%" label. A shared gallery-widget--clamp-value now feeds both halves.

Two hygiene fixes ride along. The module requires cl-lib explicitly instead of leaning on svg.el's transitive require. The token-file load resolves its directory through gallery-widget--source-dir, which falls back to default-directory when the form is re-evaluated outside a load and outside a file buffer (both location variables are nil there and file-name-directory errored).

1 files changed, 20 insertions, 5 deletions

diff --git a/docs/prototypes/gallery-widget.el b/docs/prototypes/gallery-widget.el
index 5d69148..5a80e59 100644
--- a/docs/prototypes/gallery-widget.el
+++ b/docs/prototypes/gallery-widget.el
@@ -24,9 +24,16 @@
 
 (require 'svg)
 (require 'dom)
+(require 'cl-lib)
 
-(load (expand-file-name "gallery-tokens.el"
-                        (file-name-directory (or load-file-name buffer-file-name)))
+(defun gallery-widget--source-dir ()
+  "Directory holding this module's source (and gallery-tokens.el).
+Falls back to `default-directory' when evaluated outside a load and
+outside a file buffer, where both location variables are nil."
+  (let ((src (or load-file-name buffer-file-name)))
+    (if src (file-name-directory src) default-directory)))
+
+(load (expand-file-name "gallery-tokens.el" (gallery-widget--source-dir))
       nil t)
 
 (defun gallery-widget-token (name)
@@ -43,11 +50,17 @@ a typo'd token must fail loudly, not render black."
 (defconst gallery-widget--gauge-max-deg 60.0
   "Needle angle at value 100.")
 
-(defun gallery-widget--needle-angle (value)
-  "Map VALUE (0-100, clamped) onto the gauge's needle angle in degrees."
+(defun gallery-widget--clamp-value (value)
+  "Validate VALUE is a number and clamp it to the gauge's 0-100 range.
+One clamp shared by the needle angle and the readout, so the two halves
+of the widget can never disagree at an out-of-range input."
   (unless (numberp value)
     (error "Gauge value must be a number, got %S" value))
-  (let ((v (min 100.0 (max 0.0 (float value)))))
+  (min 100.0 (max 0.0 (float value))))
+
+(defun gallery-widget--needle-angle (value)
+  "Map VALUE (0-100, clamped) onto the gauge's needle angle in degrees."
+  (let ((v (gallery-widget--clamp-value value)))
     (+ gallery-widget--gauge-min-deg
        (* (/ v 100.0)
           (- gallery-widget--gauge-max-deg gallery-widget--gauge-min-deg)))))
@@ -77,6 +90,8 @@ Positive angles swing right, matching the gauge's needle travel."
 Geometry mirrors the web card: 96px-wide semicircular dial, pivot at its
 bottom center, 40px needle sweeping -60..+60 degrees, readout below."
   (let* ((w 96) (h 64) (cx 48.0) (cy 48.0)
+         ;; clamp once; the angle and the readout render the same value
+         (value (gallery-widget--clamp-value value))
          (angle (gallery-widget--needle-angle value))
          (tip (gallery-widget--polar cx cy 40.0 angle))
          (svg (svg-create w h :viewBox (format "0 0 %d %d" w h))))