Controlling indentation

In the above examples, the indentation is still done automatically. If we want the indentation to be at the first term so that all of the operators align regardless of whether we have automatic or manual line breaks, we can do so by adding an id attribute value to the first operator that we want all subsequent lines to align to, and then setting indentalign to be id and the indenttarget to be that id as follows:

<div><tt><math xmlns='http://www.w3.org/1998/Math/MathML'<br></br>      maxwidth='200px' linebreakmultchar='×' linebreakstyle='before'<br></br>      <span>indentalign='id' indenttarget='firstOperator'</span>><br></br>  <mrow><br></br>    <mrow><br></br>      <mo>(</mo><br></br>      <mrow><br></br>        <msup><br></br>          <mi>x</mi><br></br>          <mn>4</mn><br></br>        </msup><br></br>        <mo<span>id='firstOperator'</span>>-</mo><br></br>        …<br></br></math></tt></div>

This gives the following result:

It is often sufficient to inherit the indentation target, but not where there are multiple indentation levels; in those cases, it is necessary to either wrap a mstyle around the other parts or explicitly set the indentation target on potential break points. The later technique is a good one when a linebreak is forced. Here's an example where we align both the equals sign and the left parentheses:

<math xmlns='http://www.w3.org/1998/Math/MathML'
      maxwidth='300px' linebreakmultchar='×' linebreakstyle='before'>
 <mrow>
  <msup>
   <mrow>
    <mo>(</mo>
    <mrow>
     <msup> <mi>x</mi> <mn>2</mn> </msup>
     <mo>-</mo>
     <msup> <mi>y</mi> <mn>2</mn> </msup>
    </mrow>
    <mo>)</mo>
   </mrow>
   <mn>4</mn>
  </msup>
  <mo id='equals'>=</mo>
  <mrow>
   <msup>
    <mrow>
     <mo>(</mo> <mrow> <mi>x</mi> <mo>-</mo> <mi>y</mi> </mrow> <mo>)</mo>
    </mrow>
    <mn>4</mn>
   </msup>
   <mo>&#x2062;</mo>
   <msup>
    <mrow>
     <mo>(</mo> <mrow>  <mi>x</mi> <mo>+</mo> <mi>y</mi> </mrow> <mo>)</mo>
    </mrow>
    <mn>4</mn>
   </msup>
  </mrow>
  <mo linebreak='newline' indentalign='id' indenttarget='equals'>=</mo>
  <mrow>
   <mrow>
    <mo id='lparen'>(</mo>
    <mrow>
     <msup> <mi>x</mi> <mn>4</mn> </msup>
     <mo>-</mo>
     <mrow>
      <mn>4</mn>
      <mo>&#x2062;</mo>
      <msup> <mi>x</mi> <mn>3</mn> </msup>
      <mo>&#x2062;</mo>
      <mi>y</mi>
     </mrow>
     <mo>+</mo>
     <mrow>
      <mn>6</mn>
      <mo>&#x2062;</mo>
      <msup> <mi>x</mi> <mn>2</mn> </msup>
      <mo>&#x2062;</mo>
      <msup> <mi>y</mi> <mn>2</mn> </msup>
     </mrow>
     <mo>-</mo>
     <mrow>
      <mn>4</mn>
      <mo>&#x2062;</mo>
      <mi>x</mi>
      <mo>&#x2062;</mo>
      <msup> <mi>y</mi> <mn>3</mn> </msup>
     </mrow>
     <mo>+</mo>
     <msup> <mi>y</mi> <mn>4</mn> </msup>
    </mrow>
    <mo>)</mo>
   </mrow>
   <mo linebreak='newline' indentalign='id' indenttarget='lparen' linebreakstyle='after'>&#x2062;</mo>
   <mrow>
    <mo>(</mo>
    <mrow>
     <msup> <mi>x</mi> <mn>4</mn> </msup>
     <mo>+</mo>
     <mrow>
      <mn>4</mn>
      <mo>&#x2062;</mo>
      <msup> <mi>x</mi>  <mn>3</mn> </msup>
      <mo>&#x2062;</mo>
      <mi>y</mi>
     </mrow>
     <mo>+</mo>
     <mrow>
      <mn>6</mn>
      <mo>&#x2062;</mo>
      <msup> <mi>x</mi> <mn>2</mn> </msup>
      <mo>&#x2062;</mo>
      <msup> <mi>y</mi> <mn>2</mn> </msup>
     </mrow>
     <mo>+</mo>
     <mrow>
      <mn>4</mn>
      <mo>&#x2062;</mo>
      <mi>x</mi>
      <mo>&#x2062;</mo>
      <msup> <mi>y</mi> <mn>3</mn> </msup>
     </mrow>
     <mo>+</mo>
     <msup> <mi>y</mi> <mn>4</mn> </msup>
    </mrow>
    <mo>)</mo>
   </mrow>
  </mrow>
 </mrow>
</math>