[1 mod] "fi" in PDF misses glyph under highlighting (missing ligature?)

[David Owen]

Ubuntu Desktop 10.04, ubuntu-private-fonts-0.1.6~ppa4, evince-2.30.3-0ubuntu1.1.

The document is at http://ubuntuone.com/p/7vH/ (Web Design Guidelines).

Go to page 15, "Typography on the web." Find the text "The correct global font definition is:" and notice the "fi" in "definition" is rendered correctly. Now highlight that text and notice that "fi" is replaced with a box signifying an unknown glyph.

[Tobias Wolf (towolf)]

That a bug in the PDF generating software, not Evince.

The writing software needs to set up a proper ToUnicode mapping in the PDF so that ligatures are resolved properly.

[Khaled Hosny (khaledhosny)]

It can be a font bug actually, if the ligature glyph is not named in accordance of Adobe Glyph List, it can cause such sort of things. An fi ligature should be named f_i and so.

[Paul Sladen (sladen)]

Khaled: for the specific case of 'fi', it should be mapped, see discussions on #632267 ("Technical: reverse-mapped 'μΔfifl' (detected by warning in FontForge)" and bug #652154 ("Remove: U+F001 U+F002 ligature aliases from PUA"); it's mapped per the Adobe Glyph List (which sadly means it points to the PUA, not to the Unicode codepoint as the primary).

[Matthew Paul Thomas (mpt)]

Unfortunately, with the Ubuntu One shutdown, the document cited is no longer available. I don't see it anywhere around the Ubuntu Web Design site. <http://design.ubuntu.com/web-style-guide/typography> Googling for the text in the screenshot, I find the document rendered using Flash at <http://www.docstoc.com/docs/159904573/Study-on-the-editing-and-output-2013>, but downloading the PDF requires an account of some sort.

Meanwhile, I can't generate an example of the problem myself: neither AbiWord, nor OpenOffice, nor pango-view uses the ligature for the "fi" string.

Can anyone provide an example of the problem?

[Kevin Godby (godbyk)]

I've attached a PDF generated with XeLaTeX that shows text typeset in Ubuntu with and without ligatures. I've also included a sample of Linux Libertine for comparison (since the ligatures in Ubuntu are effectively indistinguishable from the regular glyphs).

When I view this PDF in Evince, I'm able to properly select the text. (That is, I'm unable to reproduce this bug using Ubuntu font version 0.80.)

If you'd like to me to try this in another PDF viewer or if we need to generate the PDF with a different program, let me know.

[Matthew Paul Thomas (mpt)]

Thanks for that testing, Kevin! Leaving this as Incomplete so long as it isn't reproducible.

[Paul Sladen (sladen)]

Probably not the font, but bug #39890 (or one of its newer descents---evince does not highlight with the text/glyphs that are there, but by rerendering in another/different font; the classic visualisation of this is when selecting diagonal sloping text, and Evince highlights that with a staircase of vertically-oriented text.