Fix hebrew character highlight issue in a special document

There is an image object and text objects in this document, but the character in each text object is reversed.
When rendering, the image object is shown.
However, when highlighting, the text object is selected, resulting in text index issue.
Moreover, the character in the document is in reading order, which is different from normal document.

BUG=pdfium:43
R=jbreiden@google.com

Review URL: https://codereview.chromium.org/484503002

1 files changed, 6 insertions, 1 deletions

diff --git a/core/src/fpdftext/fpdf_text.cpp b/core/src/fpdftext/fpdf_text.cpp
index defad925b9..f633e19517 100644
--- a/core/src/fpdftext/fpdf_text.cpp
+++ b/core/src/fpdftext/fpdf_text.cpp
@@ -184,7 +184,12 @@ CTextBaseLine* CTextPage::InsertTextBox(CTextBaseLine* pBaseLine, FX_FLOAT basey
     while (offset < len) {
         FX_DWORD ch = pFont->GetNextChar(pStr, offset);
         CFX_WideString unicode_str = pFont->UnicodeFromCharCode(ch);
-        text += unicode_str;
+        if (unicode_str.IsEmpty()) {
+            text += (FX_WCHAR)ch;
+        }
+        else {
+            text += unicode_str;
+        }
     }
     pBaseLine->InsertTextBox(leftx, rightx, topy, bottomy, spacew, fontsize_v, text);
     return pBaseLine;