✨ Choose closest font weight for token weight when no matching weight is found

frontend/src/app/main/data/workspace/tokens/application.cljs

@@ -333,10 +333,7 @@
                            (txt/is-paragraph-node? node)))
         update-fn (fn [node _]
                     (let [font (fonts/get-font-data (:font-id node))
-                          font-variant-id (or
-                                           (fonts/find-variant font font-variant)
-                                           ;; When variant with matching weight but not with matching style (italic) is found, use that one
-                                           (fonts/find-variant font (dissoc font-variant :style)))]
+                          font-variant-id (fonts/find-closest-variant font (:weight font-variant) (:style font-variant))]
                       (if font-variant-id
                         (-> node
                             (d/txt-merge (assoc font-variant :font-variant-id (:id font-variant-id)))

frontend/src/app/main/fonts.cljs

@@ -270,6 +270,45 @@
   (let [props (keys variant-data)]
     (d/seek #(= (select-keys % props) variant-data) variants)))
 
+(defn find-closest-variant
+  "Find the closest font weight variant in `font` for `target-weight` with optional `target-style` match.
+  When exactly between two weights, choose the higher one."
+  [font target-weight target-style]
+  (when-let [target-weight (d/parse-integer target-weight)]
+    (let [variants (:variants font [])
+          result
+          (reduce
+           (fn [closest-match variant]
+             (let [weight (d/parse-integer (:weight variant))
+                   distance (abs (- target-weight weight))
+                   matches-style? (= target-style (:style variant))
+                   current {:variant variant
+                            :weight weight
+                            :distance distance}]
+               (cond
+                 ;; Exact match found
+                 (and (zero? distance)
+                      (if target-style matches-style? true))
+                 (reduced current)
+
+                 (nil? closest-match) current
+
+                 ;; Update best match if this variant is closer or equal distance but higher weight
+                 (or (< distance (:distance closest-match))
+                     (and (= distance (:distance closest-match))
+                          (> weight (:weight closest-match))))
+                 current
+
+                 ;; Same weight as the `closest-match` but the style matches `target-style`
+                 (and (= weight (:weight closest-match)) matches-style?)
+                 current
+
+                 :else
+                 closest-match)))
+           nil
+           variants)]
+      (:variant result))))
+
 ;; Font embedding functions
 (defn get-node-fonts
   "Extracts the fonts used by some node"

frontend/test/frontend_tests/fonts_test.cljs

@@ -0,0 +1,126 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC
+
+(ns frontend-tests.fonts-test
+  (:require
+   [app.main.fonts :as fonts]
+   [cljs.test :as t :include-macros true]))
+
+(def sample-font
+  {:id "sourcesanspro"
+   :name "Source Sans Pro"
+   :family "sourcesanspro"
+   :variants
+   [{:id "200"
+     :name "200"
+     :weight "200"
+     :style "normal"
+     :suffix "extralight"
+     :ttf-url "sourcesanspro-extralight.ttf"}
+    {:id "200italic"
+     :name "200 Italic"
+     :weight "200"
+     :style "italic"
+     :suffix "extralightitalic"
+     :ttf-url "sourcesanspro-extralightitalic.ttf"}
+    {:id "300"
+     :name "300"
+     :weight "300"
+     :style "normal"
+     :suffix "light"
+     :ttf-url "sourcesanspro-light.ttf"}
+    {:id "300italic"
+     :name "300 Italic"
+     :weight "300"
+     :style "italic"
+     :suffix "lightitalic"
+     :ttf-url "sourcesanspro-lightitalic.ttf"}
+    {:id "regular"
+     :name "400"
+     :weight "400"
+     :style "normal"
+     :ttf-url "sourcesanspro-regular.ttf"}
+    {:id "italic"
+     :name "400 Italic"
+     :weight "400"
+     :style "italic"
+     :ttf-url "sourcesanspro-italic.ttf"}
+    {:id "bold"
+     :name "700"
+     :weight "700"
+     :style "normal"
+     :ttf-url "sourcesanspro-bold.ttf"}
+    {:id "bolditalic"
+     :name "700 Italic"
+     :weight "700"
+     :style "italic"
+     :ttf-url "sourcesanspro-bolditalic.ttf"}
+    {:id "black"
+     :name "900"
+     :weight "900"
+     :style "normal"
+     :ttf-url "sourcesanspro-black.ttf"}
+    {:id "blackitalic"
+     :name "900 Italic"
+     :weight "900"
+     :style "italic"
+     :ttf-url "sourcesanspro-blackitalic.ttf"}]
+   :backend :builtin})
+
+(t/deftest find-closest-weight-variant-test
+  (t/testing "finds exact weight match"
+    (let [result (fonts/find-closest-variant sample-font "400" nil)]
+      (t/is (= "400" (:weight result)))
+      (t/is (= "normal" (:style result)))))
+
+  (t/testing "finds exact weight match with style"
+    (let [result (fonts/find-closest-variant sample-font "400" "italic")]
+      (t/is (= "400" (:weight result)))
+      (t/is (= "italic" (:style result)))))
+
+  (t/testing "chooses higher weight when exactly between two weights"
+    (let [result (fonts/find-closest-variant sample-font "350" nil)]
+      (t/is (= "400" (:weight result)))))
+
+  (t/testing "finds exact weight match with style"
+    (let [result (fonts/find-closest-variant sample-font "350" "italic")]
+      (t/is (= "400" (:weight result)))
+      (t/is (= "italic" (:style result)))))
+
+  (t/testing "finds closest weight below minimum available"
+    (let [result (fonts/find-closest-variant sample-font "0" nil)]
+      (t/is (= "200" (:weight result)))))
+
+  (t/testing "finds closest weight above maximum available"
+    (let [result (fonts/find-closest-variant sample-font "1000" nil)]
+      (t/is (= "900" (:weight result)))))
+
+  (t/testing "keeps the closest weight match when style is not found"
+    (let [font {:id "sourcesanspro"
+                :name "Source Sans Pro"
+                :family "sourcesanspro"
+                :variants
+                [{:id "200italic"
+                  :name "200 Italic"
+                  :weight "200"
+                  :style "italic"
+                  :suffix "extralightitalic"
+                  :ttf-url "sourcesanspro-extralightitalic.ttf"}
+                 {:id "300"
+                  :name "300"
+                  :weight "300"
+                  :style "normal"
+                  :suffix "light"
+                  :ttf-url "sourcesanspro-light.ttf"}
+                 {:id "300italic"
+                  :name "300 Italic"
+                  :weight "300"
+                  :style "italic"
+                  :suffix "lightitalic"
+                  :ttf-url "sourcesanspro-lightitalic.ttf"}]}
+          result (fonts/find-closest-variant font "200" nil)]
+      (t/is (= "200" (:weight result)))
+      (t/is (= "italic" (:style result))))))