"Missing glyph"-sign is shown for line feed in IE11

[RoelN]

If I create a font with fontcustom, line feeds are showing a "missing glyph"-symbol in Internet Explorer 11. These will be an actual new line, but the previous line will show a rectangle.

You can reproduce this quickly by going to the http://fontcustom.com/ website and editing the :before content with the F12-tools. If you take the first icon you should change

.icon-browser:before {
    content: "\f100";
}

to

.icon-browser:before {
    content: "\f100 \a test";
    white-space: pre;
}

to see the effect. Here's a screenshot of what will happen in IE11:

Other browsers are fine. I checked the glyf table and 0x0a is mapped to .notdef, which is the same for other (icon) fonts. But the rectangle only shows up for fonts created with fontcustom.

[RoelN]

Ok, the problem is with the fact that no glyph for 0x20 (space) has been defined. The problem can also be reproduced when you use a space in the icon container.

I fixed it manually for my font. First I tried adding it to .fontcustom-manifest.json and mapping space to an empty SVG, but this caused some misalignment with my other glyphs.

So I started editing the TTF with TTX/FontTools and removed all unused charcters:

<GlyphID id="0" name=".notdef"/>
<GlyphID id="1" name=".null"/>
<GlyphID id="2" name="nonmarkingreturn"/>
<GlyphID id="3" name="hyphen"/>

I removed them from the hmtx, cmap and glyf tables as well, and added added the space character there.

The glyph for the space character I used:

<TTGlyph name="space" xMin="0" yMin="0" xMax="0" yMax="0">
  <contour>
    <pt x="0" y="0" on="1"/>
    <pt x="0" y="0" on="1"/>
    <pt x="0" y="0" on="1"/>
  </contour>
  <instructions><assembly>
    </assembly></instructions>
</TTGlyph>

Turning this back into a TTF font results in a proper font.

Proposed solution for fontcustom: add this space char by default.