From 333b88a8a76801e03545a2404a15a1c2ed5fcb4f Mon Sep 17 00:00:00 2001
From: Lukas Hollaender <lukas.hollaender@yworks.com>
Date: Tue, 16 Sep 2025 13:55:11 +0200
Subject: [PATCH] fix scaling of form object bounding boxes

---
 src/jspdf.js                                 |  50 ++++++++++++-------
 test/reference/form-objects-scale-factor.pdf | Bin 0 -> 3419 bytes
 test/specs/form-objects.spec.js              |  25 ++++++++++
 3 files changed, 57 insertions(+), 18 deletions(-)
 create mode 100644 test/reference/form-objects-scale-factor.pdf
 create mode 100644 test/specs/form-objects.spec.js

diff --git a/src/jspdf.js b/src/jspdf.js
index ac63154c5..f91dd396f 100644
--- a/src/jspdf.js
+++ b/src/jspdf.js
@@ -5711,8 +5711,8 @@ function jsPDF(options) {
     this.x = pageX;
     this.y = pageY;
     this.matrix = pageMatrix;
-    this.width = getPageWidth(currentPage);
-    this.height = getPageHeight(currentPage);
+    this.width = getUnscaledPageWidth(currentPage);
+    this.height = getUnscaledPageHeight(currentPage);
     this.outputDestination = outputDestination;
 
     this.id = ""; // set by endFormObject()
@@ -5727,8 +5727,8 @@ function jsPDF(options) {
     pageX = this.x;
     pageY = this.y;
     pageMatrix = this.matrix;
-    setPageWidth(currentPage, this.width);
-    setPageHeight(currentPage, this.height);
+    setPageWidthWithoutScaling(currentPage, this.width);
+    setPageHeightWithoutScaling(currentPage, this.height);
     outputDestination = this.outputDestination;
   };
 
@@ -5953,32 +5953,46 @@ function jsPDF(options) {
     }
   }
 
-  var getPageWidth = (API.getPageWidth = function(pageNumber) {
-    pageNumber = pageNumber || currentPage;
+  function getUnscaledPageWidth(pageNumber) {
+    return (
+      pagesContext[pageNumber].mediaBox.topRightX -
+      pagesContext[pageNumber].mediaBox.bottomLeftX
+    );
+  }
+
+  function setPageWidthWithoutScaling(pageNumber, value) {
+    pagesContext[pageNumber].mediaBox.topRightX =
+      value + pagesContext[pageNumber].mediaBox.bottomLeftX;
+  }
+
+  function getUnscaledPageHeight(pageNumber) {
     return (
-      (pagesContext[pageNumber].mediaBox.topRightX -
-        pagesContext[pageNumber].mediaBox.bottomLeftX) /
-      scaleFactor
+      pagesContext[pageNumber].mediaBox.topRightY -
+      pagesContext[pageNumber].mediaBox.bottomLeftY
     );
+  }
+
+  function setPageHeightWithoutScaling(pageNumber, value) {
+    pagesContext[pageNumber].mediaBox.topRightY =
+      value + pagesContext[pageNumber].mediaBox.bottomLeftY;
+  }
+
+  var getPageWidth = (API.getPageWidth = function(pageNumber) {
+    pageNumber = pageNumber || currentPage;
+    return getUnscaledPageWidth(pageNumber) / scaleFactor;
   });
 
   var setPageWidth = (API.setPageWidth = function(pageNumber, value) {
-    pagesContext[pageNumber].mediaBox.topRightX =
-      value * scaleFactor + pagesContext[pageNumber].mediaBox.bottomLeftX;
+    setPageWidthWithoutScaling(pageNumber, value * scaleFactor);
   });
 
   var getPageHeight = (API.getPageHeight = function(pageNumber) {
     pageNumber = pageNumber || currentPage;
-    return (
-      (pagesContext[pageNumber].mediaBox.topRightY -
-        pagesContext[pageNumber].mediaBox.bottomLeftY) /
-      scaleFactor
-    );
+    return getUnscaledPageHeight(pageNumber) / scaleFactor;
   });
 
   var setPageHeight = (API.setPageHeight = function(pageNumber, value) {
-    pagesContext[pageNumber].mediaBox.topRightY =
-      value * scaleFactor + pagesContext[pageNumber].mediaBox.bottomLeftY;
+    setPageHeightWithoutScaling(pageNumber, value * scaleFactor);
   });
 
   /**
diff --git a/test/reference/form-objects-scale-factor.pdf b/test/reference/form-objects-scale-factor.pdf
new file mode 100644
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GIT binary patch
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diff --git a/test/specs/form-objects.spec.js b/test/specs/form-objects.spec.js
new file mode 100644
index 000000000..988bebc2c
--- /dev/null
+++ b/test/specs/form-objects.spec.js
@@ -0,0 +1,25 @@
+/* global jsPDF */
+
+describe("Form objects", () => {
+  beforeAll(loadGlobals);
+
+  it("should use correct bounding box for scale factors other than 1", () => {
+    const doc = new jsPDF({ unit: "mm", format: [200, 200], orientation: "p" });
+
+    doc.advancedAPI();
+
+    doc.beginFormObject(-50, -50, 100, 100, doc.unitMatrix);
+    doc.rect(-50, -50, 100, 100).fill();
+    doc.endFormObject("0");
+
+    doc.doFormObject("0", new doc.Matrix(1, 0, 0, 1, 100, 100));
+
+    doc.setDrawColor(255, 0, 0);
+    doc.rect(50, 50, 100, 100).stroke();
+    doc.rect(0, 0, 200, 200).stroke();
+
+    doc.compatAPI();
+
+    comparePdf(doc.output(), "form-objects-scale-factor.pdf", "form-objects");
+  });
+});