Add fontLayoutCache option

lib/font/embedded.js

@@ -23,7 +23,9 @@ class EmbeddedFont extends PDFFont {
     this.lineGap = this.font.lineGap * this.scale;
     this.bbox = this.font.bbox;
 
-    this.layoutCache = Object.create(null);
+    if (document.options.fontLayoutCache !== false) {
+      this.layoutCache = Object.create(null);
+    }
   }
 
   layoutRun(text, features) {
@@ -43,6 +45,9 @@ class EmbeddedFont extends PDFFont {
   }
 
   layoutCached(text) {
+    if (!this.layoutCache) {
+      return this.layoutRun(text);
+    }
     let cached;
     if ((cached = this.layoutCache[text])) {
       return cached;

tests/unit/font.spec.js

@@ -0,0 +1,36 @@
+const PDFFontFactory = require('../../lib/font_factory').default;
+const PDFDocument = require('../../lib/document').default;
+
+describe('EmbeddedFont', () => {
+  test('no fontLayoutCache option', () => {
+    const document = new PDFDocument();
+    const font = PDFFontFactory.open(
+      document,
+      'tests/fonts/Roboto-Regular.ttf'
+    );
+    const runSpy = jest.spyOn(font, 'layoutRun');
+
+    font.layout('test');
+    font.layout('test');
+    font.layout('test');
+    font.layout('test');
+
+    expect(runSpy).toBeCalledTimes(1);
+  });
+
+  test('fontLayoutCache = false', () => {
+    const document = new PDFDocument({ fontLayoutCache: false });
+    const font = PDFFontFactory.open(
+      document,
+      'tests/fonts/Roboto-Regular.ttf'
+    );
+    const runSpy = jest.spyOn(font, 'layoutRun');
+
+    font.layout('test');
+    font.layout('test');
+    font.layout('test');
+    font.layout('test');
+
+    expect(runSpy).toBeCalledTimes(4);
+  });
+});