Noto Nastaliq Urdu has many phantom (empty) glyphs

[GoogleCodeExporter]

Copying from
http://lists.cairographics.org/archives/cairo/2014-November/025824.html

Something I noticed while debugging
this is hb-view appears to be emitting a lot of empty glyphs. In large
documents this will unnecessarily increase the file size and increase
rendering time.

Adding some debug to cairo_show_text_glyphs and using the sample text:

کے

I get:

cairo_show_text_glyphs   num_glyphs: 5
   glyph 0: 1005
   glyph 1: 1006
   glyph 2: 1007
   glyph 3: 248
   glyph 4: 409

Using ttx I can see that

 <mtx name="glyph01005" width="0" lsb="0"/>
 <mtx name="glyph01006" width="0" lsb="0"/>
 <mtx name="glyph01007" width="0" lsb="0"/>

and

<TTGlyph name="glyph01005" xMin="0" yMin="0" xMax="0" yMax="0">
  <contour>
    <pt x="0" y="0" on="1"/>
  </contour>
  <instructions><assembly>
  </assembly></instructions>
</TTGlyph>

<TTGlyph name="glyph01006" xMin="0" yMin="0" xMax="0" yMax="0">
  <contour>
    <pt x="0" y="0" on="1"/>
  </contour>
  <instructions><assembly>
    </assembly></instructions>
</TTGlyph>

<TTGlyph name="glyph01007" xMin="0" yMin="0" xMax="0" yMax="0">
  <contour>
    <pt x="0" y="0" on="1"/>
  </contour>
  <instructions><assembly>
  </assembly></instructions>
</TTGlyph>

Original issue reported on code.google.com by behdad@google.com on 25 Nov 2014 at 7:04

[behdad]

cc @behdad

[kmansourMT]

The font includes a considerable number of what-seem-to-be-empty glyphs that function as control characters, and are required for correct rendering.

[behdad]

While it's possible to remove those, I don't think there's any problem with leaving them there.