Created attachment 206790 [details]
<math display="block"> and <math display="inline"> currently display the formula as a block or inline box. However, they should also set the initial value of displaystyle to true and false respectively. The displaystyle value can also be set via an explicit displaystyle attribute and is reset to false by some elements (like mfrac, scripts, roots etc). When displaystyle=true, the operators marked largeop (either via an explicit attribute or as computed from the operator dictionary) should be drawn larger. When displaystyle=false, the operators marked movablelimits (either via an explicit attribute or as computed from the operator dictionary) should have its under/over limits drawn as sub/sup. See the testcase, where a sum symbol is used (largeop and movablelimits per the operator dictionary).
See also bucket 3 of the MathML Acid3 tests:
See chapter 3 of the MathML spec for details:
Displaystyle maybe be involved in other cases (e.g. in scriptlevel incrementation, see bug 49309) but I think we now support the most important cases (largeop, movablelimits and some choice of MATH constants). So I guess we can close this bug.