From 67f3972bf0f55185831bcf2998848736255146f9 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 13 Mar 2026 09:47:20 +0100
Subject: [PATCH] Add a private `FontInfo` helper method for reading array-data
 (PR 20197 follow-up)

Currently the `bbox`, `fontMatrix`, and `defaultVMetrics` getters duplicate almost the same code, which we can avoid by adding a new helper method (similar to existing ones for reading numbers and strings).

The added `assert` in the new helper method also caught a bug in how the `defaultVMetrics` length was compiled.
---
 src/core/obj_bin_transform_core.js       |  2 +-
 src/display/obj_bin_transform_display.js | 63 +++++++++++-------------
 2 files changed, 31 insertions(+), 34 deletions(-)

diff --git a/src/core/obj_bin_transform_core.js b/src/core/obj_bin_transform_core.js
index e2f70214d..b9cbd75ac 100644
--- a/src/core/obj_bin_transform_core.js
+++ b/src/core/obj_bin_transform_core.js
@@ -192,7 +192,7 @@ function compileFontInfo(font) {
   );
 
   if (font.defaultVMetrics) {
-    view.setUint8(offset++, 1);
+    view.setUint8(offset++, 3);
     for (const metric of font.defaultVMetrics) {
       view.setInt16(offset, metric, true);
       offset += 2;
diff --git a/src/display/obj_bin_transform_display.js b/src/display/obj_bin_transform_display.js
index 9376f09a9..2068b13ed 100644
--- a/src/display/obj_bin_transform_display.js
+++ b/src/display/obj_bin_transform_display.js
@@ -198,49 +198,46 @@ class FontInfo {
     return this.#readNumber(2);
   }
 
-  get bbox() {
-    let offset = FONT_INFO.OFFSET_BBOX;
-    const numCoords = this.#view.getUint8(offset);
-    if (numCoords === 0) {
+  #readArray(offset, arrLen, lookupName, increment) {
+    const len = this.#view.getUint8(offset);
+    if (len === 0) {
       return undefined;
     }
+    assert(len === arrLen, "Invalid array length.");
     offset += 1;
-    const bbox = [];
-    for (let i = 0; i < 4; i++) {
-      bbox.push(this.#view.getInt16(offset, true));
-      offset += 2;
+    const arr = new Array(len);
+    for (let i = 0; i < len; i++) {
+      arr[i] = this.#view[lookupName](offset, true);
+      offset += increment;
     }
-    return bbox;
+    return arr;
+  }
+
+  get bbox() {
+    return this.#readArray(
+      /* offset = */ FONT_INFO.OFFSET_BBOX,
+      /* arrLen = */ 4,
+      /* lookup = */ "getInt16",
+      /* increment = */ 2
+    );
   }
 
   get fontMatrix() {
-    let offset = FONT_INFO.OFFSET_FONT_MATRIX;
-    const numPoints = this.#view.getUint8(offset);
-    if (numPoints === 0) {
-      return undefined;
-    }
-    offset += 1;
-    const fontMatrix = [];
-    for (let i = 0; i < 6; i++) {
-      fontMatrix.push(this.#view.getFloat64(offset, true));
-      offset += 8;
-    }
-    return fontMatrix;
+    return this.#readArray(
+      /* offset = */ FONT_INFO.OFFSET_FONT_MATRIX,
+      /* arrLen = */ 6,
+      /* lookup = */ "getFloat64",
+      /* increment = */ 8
+    );
   }
 
   get defaultVMetrics() {
-    let offset = FONT_INFO.OFFSET_DEFAULT_VMETRICS;
-    const numMetrics = this.#view.getUint8(offset);
-    if (numMetrics === 0) {
-      return undefined;
-    }
-    offset += 1;
-    const defaultVMetrics = [];
-    for (let i = 0; i < 3; i++) {
-      defaultVMetrics.push(this.#view.getInt16(offset, true));
-      offset += 2;
-    }
-    return defaultVMetrics;
+    return this.#readArray(
+      /* offset = */ FONT_INFO.OFFSET_DEFAULT_VMETRICS,
+      /* arrLen = */ 3,
+      /* lookup = */ "getInt16",
+      /* increment = */ 2
+    );
   }
 
   #readString(index) {