PDF Viewer bug using Arial font where whitespaces became "question mark"

I didn't notice this bug until I run it in Google Chrome in Windows 7. It wasn't noticeable in Internet Explorer cuz it was using Adobe Acrobat, but Chrome use built-in PDF Viewer.

The text "Hello, How are you?" had became "Hello,?How?are?you?".

using pdfclownFonts = org.pdfclown.documents.contents.fonts;

private void DocumentTemplate(Document parmDocument)
{
    PrimitiveComposer primitiveComposer = new PrimitiveComposer(page);
    {
        BlockComposer blockComposer = new BlockComposer(primitiveComposer);
        pdfclownFonts::Font fontArial = pdfclownFonts::Font.Get(parmDocument, _fontArialRegularFilePath);
        primitiveComposer.SetFont(fontArial, 26 /*[Font-Size]*/);

        blockComposer.Begin(New RectangleF(5f, 5f, 500f, 30f), XAlignmentEnum.Left, YAlignment Enum.Top);
        blockComposer.ShowText("Hello, How are you?");
        blockComposer.End();

        blockComposer.Flush();
    }
}

Then I found this bug report at http://sourceforge.net/p/clown/bugs/52/ .

So my question is...

1) Is it just a Chrome bug?

2) Or is it just a PDFClown bug?

3) If PDFClown bug, then do you have any idea of estimate time will it be fixed?

Thanks.

Solution

This issue is masterly explained by Vadim in his answer and was the subject of at least one pdf.js' bug-tracking entry.

The short answer is that PDF Clown generates perfectly legal PDF files (hence they are properly rendered by Adobe Acrobat, Poppler-based viewers like Evince, and even the excellent Ghostscript interpreter). The problem is that these PDF files feature "jagged" mixed-length code-points which aren't properly handled by less-mature viewers like Chrome's.

To avoid such an inconvenience, PDF Clown will use single-length encodings only (it's among the issues due to be solved in 0.2.0).

UPDATE 04/14/2015

I'm glad to announce that the issue has been solved and committed to the project's repo. It will be included in next releases (0.1.2.1 and 0.2.0); in the meantime, you can download a code snapshot from the link indicated.