Don't assume "fill in the blank" for spacing around mtext

[NSoiffer]

I found the following in a TeX translation from a textbook. The author was trying to add a lot of space around the word "or", but the Nemeth turned this into "fill in the blank". That happens for UEB and maybe other braille codes.

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mstyle displaystyle="true" scriptlevel="0">
    <mfrac>
      <mn>1</mn>
      <mn>2</mn>
    </mfrac>
  </mstyle>
  <mo stretchy="false">(</mo>
  <mi>p</mi>
  <mo>+</mo>
  <mi>q</mi>
  <mo stretchy="false">)</mo>
  <mtext>&#xA0;</mtext>
  <mtext>&#xA0;</mtext>
  <mtext>&#xA0;</mtext>
  <mtext>&#xA0;</mtext>
  <mtext>or</mtext>
  <mtext>&#xA0;</mtext>
  <mtext>&#xA0;</mtext>
  <mtext>&#xA0;</mtext>
  <mtext>&#xA0;</mtext>
  <mstyle displaystyle="true" scriptlevel="0">
    <mfrac>
      <mrow>
        <mi>p</mi>
        <mo>+</mo>
        <mi>q</mi>
      </mrow>
      <mn>2</mn>
    </mfrac>
  </mstyle>
</math>

MathCAT canonicalizes that by collapsing the spaces:

 <math display='block'>
  <mrow data-changed='added'>
    <mfrac displaystyle='true' scriptlevel='0'>
      <mn>1</mn>
      <mn>2</mn>
    </mfrac>
    <mo data-changed='added'>&#x2062;</mo>
    <mrow data-changed='added'>
      <mo stretchy='false'>(</mo>
      <mrow data-changed='added'>
        <mi>p</mi>
        <mo>+</mo>
        <mi>q</mi>
      </mrow>
      <mo stretchy='false'>)</mo>
    </mrow>
    <mo data-changed='added'>&#x2062;</mo>
    <mtext data-previous-space-width='2.800'>or</mtext>
    <mo data-changed='added'>&#x2062;</mo>
    <mfrac displaystyle='true' scriptlevel='0' data-previous-space-width='2.800'>
      <mrow>
        <mi>p</mi>
        <mo>+</mo>
        <mi>q</mi>
      </mrow>
      <mn>2</mn>
    </mfrac>
  </mrow>
 </math>

Ignoring the preceding space is easy because data-previous-space-width is added to an mtext. Catching the following spaces is a little trickier.

A similar problem happens with leading a trailing spaces that the textbook also uses:

<math>
  <mtext> </mtext><mtext> </mtext><mi>x</mi><mtext> </mtext><mtext> </mtext>
</math>

This canonicalizes to:

<math>
  <mi data-previous-space-width='1.400' data-following-space-width='1.400'>x</mi>
</math>

Here are some larger examples with spaces at the start or at the end

<math><mtext> </mtext><mtext> </mtext><mn>2</mn><mo>+</mo><mi>x</mi></math>

which goes to

 <math>
  <mrow data-changed='added'>
    <mrow data-changed='added'>
      <mn data-previous-space-width='1.400'>2</mn>
      <mo>+</mo>
      <mi>x</mi>
    </mrow>
    <mo>?</mo>
  </mrow>
 </math>

At the end:

<math><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mn>9</mn><mtext> </mtext><mtext> </mtext><mtext> </mtext><mtext> </mtext><mtext> </mtext></math>

which goes to

 <math display='block'>
  <mrow data-changed='added'>
    <msup>
      <mi>x</mi>
      <mn>2</mn>
    </msup>
    <mo>+</mo>
    <mn data-following-space-width='3.500'>9</mn>
  </mrow>
 </math>