Merge pull request #14213 from Snuffleupagus/issue-11656

Tweak the Bidi-detection heuristics for very short RTL strings (issue 11656)

src/core/bidi.js

@@ -158,7 +158,8 @@ function bidi(str, startLevel = -1, vertical = false) {
 
   // Detect the bidi method
   // - If there are no rtl characters then no bidi needed
-  // - If less than 30% chars are rtl then string is primarily ltr
+  // - If less than 30% chars are rtl then string is primarily ltr,
+  //   unless the string is very short.
   // - If more than 30% chars are rtl then string is primarily rtl
   if (numBidi === 0) {
     isLTR = true;
@@ -166,7 +167,7 @@ function bidi(str, startLevel = -1, vertical = false) {
   }
 
   if (startLevel === -1) {
-    if (numBidi / strLength < 0.3) {
+    if (numBidi / strLength < 0.3 && strLength > 4) {
       isLTR = true;
       startLevel = 0;
     } else {

test/pdfs/.gitignore

@@ -448,6 +448,7 @@
 !annotation-square-circle-without-appearance.pdf
 !annotation-stamp.pdf
 !issue14048.pdf
+!issue11656.pdf
 !annotation-fileattachment.pdf
 !annotation-text-widget.pdf
 !annotation-choice-widget.pdf

test/test_manifest.json

@@ -5080,6 +5080,12 @@
       "lastPage": 1,
       "type": "eq"
     },
+    {  "id": "issue11656",
+       "file": "pdfs/issue11656.pdf",
+       "md5": "82d5d4f5978a4974707deb1ea98e62f2",
+       "rounds": 1,
+       "type": "text"
+    },
     {  "id": "vertical",
       "file": "pdfs/vertical.pdf",
       "md5": "8a74d33504701edcefeef2afd022765e",

test/unit/bidi_spec.js

@@ -16,6 +16,28 @@
 import { bidi } from "../../src/core/bidi.js";
 
 describe("bidi", function () {
+  it(
+    "should mark text as LTR if there's only LTR-characters, " +
+      "when the string is very short",
+    function () {
+      const str = "foo";
+      const bidiText = bidi(str, -1, false);
+
+      expect(bidiText.str).toEqual("foo");
+      expect(bidiText.dir).toEqual("ltr");
+    }
+  );
+
+  it("should mark text as LTR if there's only LTR-characters", function () {
+    const str = "Lorem ipsum dolor sit amet, consectetur adipisicing elit.";
+    const bidiText = bidi(str, -1, false);
+
+    expect(bidiText.str).toEqual(
+      "Lorem ipsum dolor sit amet, consectetur adipisicing elit."
+    );
+    expect(bidiText.dir).toEqual("ltr");
+  });
+
   it("should mark text as RTL if more than 30% of text is RTL", function () {
     // 33% of test text are RTL characters
     const test = "\u0645\u0635\u0631 Egypt";
@@ -34,4 +56,16 @@ describe("bidi", function () {
     expect(bidiText.str).toEqual(result);
     expect(bidiText.dir).toEqual("ltr");
   });
+
+  it(
+    "should mark text as RTL if less than 30% of text is RTL, " +
+      "when the string is very short (issue 11656)",
+    function () {
+      const str = "()\u05d1("; // 25% of the string is RTL characters.
+      const bidiText = bidi(str, -1, false);
+
+      expect(bidiText.str).toEqual("(\u05d1)(");
+      expect(bidiText.dir).toEqual("rtl");
+    }
+  );
 });