[NTG-context] larger dot for \dot ?

Sanjoy Mahajan sanjoy at MIT.EDU
Tue May 20 11:48:15 CEST 2014

My students complain that the dot in, for example, $\dot M$ is too small
and that they easily miss it.  So I have been trying to make a bigger
one, but haven't found a solution that plays nicely with the surrounding
math.

For example,

\def\mydot{\overset{\externalfigure[dot.pdf]}} %bigger than usual one
\def\Vdot{\mydot V}
\starttext
$\rho\Vdot\omega$  % loose spacing

$\rho V\omega$ % tighter spacing
\stoptext

where dot.pdf is a circle of radius 0.8bp (attached).

But the \Vdot gets wrapped in an hbox (inside \overset), so the
surrounding space is too large.

I also tried a metafun approach

\startuniqueMPgraphic{math:mydot}
fill unitcircle scaled 2 shifted (OverlayWidth/2-1,OverlayHeight+OverlayOffset);
path q;
q:= unitsquare xscaled OverlayWidth yscaled (OverlayHeight+OverlayOffset+1);
setbounds currentpicture to q;
\stopuniqueMPgraphic

\definemathornament [mathmydot] [mp=math:mydot]

\starttext

$\rho\mathmydot{V}\omega$

$\rho V\omega$

$\rho\mathmydot{V}_0^2\omega$

$\rho\dot{V}_0^2\omega$

\stoptext

The $\rho\mathmydot{V}\omega$ looks good.  But the subscripted _0 is not
tucked under the V, because the bounds of the character are now a
rectangle that doesn't know about its shape.  I think for a similar
reason the superscripted 2 is quite high.

Is there more math-friendly (and elegant) way to get a fatter dot?

-Sanjoy