Re: Rendering Question

From: Mark Davis (
Date: Fri Apr 26 1996 - 15:38:44 EDT

Subject: RE>Rendering Question Time: 11:29 Date:

As you say, (1) and (2) are very bad; (2) is also non-conformant.

Either (3), (4) or (5) are reasonable. For (5), we have a variation. For any
unrenderable character, we print a rounded rectangle with a symbol inside. The
symbol indicates the class of missing character, with a letter or symbol from
each block in Unicode. We do this with a "Last Resort" font, which itself has
a fairly small number of glyphs, so is easily supported. (I can look at
distributing the Last Resort font if people are interested.)

A variation on that, sparked by your question, would be to put the base
character into the rounded rectangle (perhaps also making the rectangle
dotted) to indicate a missing precomposite or its equivalent combining
character sequence.


Date: 04/25/96 18:34
To: Mark Davis
From: Dean Abramson
I'd like to take a poll to find out what people recommend
for rendering a letter that includes a combining diacritic in
a case where only the base letter is available.

For example, take the following letter
which may also be represented by the sequence

But lets say I am limited to a font that contains a small o,
but not a precomposed o diaeresis and not a combining
nonspacing diaresis. It is evident that this letter can't be
rendered ideally correctly.

Let me add that the concept of equivalent characters is
extremely important to me, therefore I would expect the
rendering of any sequence of equivalent characters to result
in an identical rendering. As such, I won't ever choose
one rendering or another depending on the sequence.

This leaves a few possible options, assuming we don't change
to any other font.

1) Render nothing.
2) Render the o and nothing more.
3) Render the o and render a box to the right of the o.
4) Render the o and render a box on top of the o.
5) Render a box.

Of course, when I say render a box, I am referring to any general
way of indicating a non-renderable character. A box is probably
the most common way.

1) I would never do.
2) The user may not be aware there is any problem so this doesn't
seem like a good choice.
3) Not bad.
4) Maybe better, but may not be easily done with many fonts.
5) Not bad.

Which would be most in keeping with the intentions and guidelines
of Unicode and appropriate rendering behavior?


Dean A.

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