PuTTY semi-bug win-fixed-ttf-underline

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summary: When using some bitmap TrueType fonts, underlined characters vanish
class: semi-bug: This might or might not be a bug, depending on your precise definition of what a bug is.
present-in: 0.59 2007-04-10

Reported by a user:

This one's a bit hard to explain, so here it goes:

  Client: PuTTY 0.59, and current snapshots
      OS: Windows XP Professional SP2
Protocol: SSHv2
  Server: FreeBSD 6.2-STABLE

Quite a few people (myself included) use the famous xterm 6x13 terminal
font on Windows (converted using Fontforge from the original 6x13.bdf to
an OpenType/TTF Bitmap font) with PuTTY.  This font contains a very
large glyph set, and line drawing characters, thus is quite useful.

All gylphs are shown correctly with this font... except for characters
which should be displayed with underlines (ex: \e[4m).  The underlines
are shown, but the gylph is blank/empty.  PuTTY does not appear to be
"drawing its own underline" with this font -- yeah I've read the code,
and this font does not suffer from the same problem "Courier New" 9pt
does (see some of the debug output I added below).

The font size selected must be 10pt.  All other point sizes (9pt, 11pt,
etc.) show the gylphs and show underlining.  Of course, the font is
intended to be used in 10pt...

The PuTTY client "Translation" mode (e.g. ISO-8859-1, UTF-8, etc.) has
no effect on this problem either -- it happens in all translations.

The font metrics are indeed 6x13, and I've verified as such with some
debugging code I threw into windows/window.c a few hours ago.  The
applicable font details:

Primary font H=13, AW=6, MW=4
  tmHeight          = 13
  tmAscent          = 11
  tmDescent         = 2
  tmInternalLeading = 0
  tmExternalLeading = 1
  tmAveCharWidth    = 6
  tmMaxCharWidth    = 4
  tmWeight          = 500
  tmOverhang        = 0
  tmItalic          = 0
  tmUnderlined      = 0
  tmStruckOut       = 0
  tmPitchAndFamily  = 0x36
  tmCharSet         = 0

I'm ~99% positive this is not the result of a badly converted font.
Other applications work just fine with this font: Wordpad, mIRC,
Internet Explorer, and SecureCRT all function normally with this font,
with underlining.  Here's a screenshot of `man ls` which should speak
for itself:


The font itself is available here:


I have been hacking at the PuTTY code for the past 6 hours trying to
figure out why this is happening, and I am completely stumped.

The only thing I *have* found:

In init_fonts(), forcing PuTTY to draw the underline itself and thus
deleting fonts[FONT_UNDERLINE] causes the problem to disappear.  I have no
explanation for why.  In windows/window.c around line 1481 -- before
the if (bold_mode == BOLD_FONT) check...

und_mode = UND_LINE;
fonts[FONT_UNDERLINE] = 0;

Again, don't know why this helps solve the issue, but it does.  This
isn't the correct "fix" obviously -- I'm just pointing it out to help
track down the source of the problem (I hope).

Another report: 20080624013622.GC26675@pihost.us
Audit trail for this semi-bug.

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(last revision of this bug record was at 2008-07-19 16:44:50 +0000)