Thank you very much Aditya for looking into this. But I still have the same
baseline grid offset problem. Interestingly, when I remove the columns, the
text shifts downwards by two lines.
My code:

\definemeasure[xheight][0.1in]

\definemeasure[base][3\measured{xheight}]


% Since all distances are in terms of base units, specify the paper size in
those

% terms as well.

\definepapersize[slide][width=26\measured{base},height=20\measured{base}]

\setuppapersize[slide]


\setupinterlinespace[line=\measure{base}]


\setuplayout

[

topspace=2\measured{base},

header=\zeropoint,

headerdistance=\zeropoint,

height=middle, % Space for 20-4=16 lines

footerdistance=\zeropoint,

footer=\zeropoint,

bottomspace=2\measured{base},

%

cutspace=2\measured{base},

leftmargin=\zeropoint,

leftmargindistance=\zeropoint,

width=middle, % space for 26-4=22 col

rightmargindistance=\zeropoint,

rightmargin=\zeropoint,

backspace=2\measured{base}

grid=yes,

]



\showframe

\showgrid


\starttext

\input tufte

\stoptext


I'm attaching the pdf output.

On Fri, May 27, 2022 at 5:00 PM Aditya Mahajan <adityam@umich.edu> wrote:

> On Wed, 25 May 2022, Stefan Nedeljkovic via ntg-context wrote:
>
> > Dear list,
> >
> > My adventures into the world of grids continue. In the linked file
> > (slide_grid_overlay.pdf) there are two things I cannot yet achieve:
> >
> >     1. I want the baseline grid to evenly (vertically) divide the text
> > area, but my code produces a smaller height of the first line and an
> > additional space at the bottom.
>
> You did not set footerdistance to zero. So, that takes up some space.
>
> >     2. The number of columns is 21.5, that is the first column is 0.5
> units
> > wide and the rest are 1 unit wide.
>
> I believe that columns has to be an integer. Why do you want fractional
> columns? Columns are useful because you can say:
>
> \setlayer[name][line=2,column=3]{....}
>
> for absolute positioning of layers. So, you can always use:
>
> \setlayer[name][line=2,column=3,x=0.5\measured{base}]{....}
>
> to move everything to the right by 0.5 units.
>
> Another option is not to use columns at all, and simply do:
>
> \setlayer[name][line=2,x=3.5\measured{base}]
>
> which will place the layer at 3.5 units from the left edge of the text
> area.
>
> > Here is what I got right now:
>
> Currently your textwidth is not a multiple of base units. I have tweaked
> the code below so that it is.
>
> \definemeasure[xheight][0.1in]
> \definemeasure[base][3\measured{xheight}]
>
> % Since all distances are in terms of base units, specify the paper size
> in those
> % terms as well.
> \definepapersize[slide][width=26\measured{base},height=20\measured{base}]
> \setuppapersize[slide]
>
> \setupinterlinespace[line=\measure{base}]
>
> \setuplayout
>     [
>       topspace=2\measured{base},
>       header=\zeropoint,
>       headerdistance=\zeropoint,
>       height=middle, % Space for 20-4=16 lines
>       footerdistance=\zeropoint,
>       footer=\zeropoint,
>       bottomspace=2\measured{base},
>       %
>       cutspace=2\measured{base},
>       leftmargin=\zeropoint,
>       leftmargindistance=\zeropoint,
>       width=middle, % space for 26-4=22 col
>       rightmargindistance=\zeropoint,
>       rightmargin=\zeropoint,
>       backspace=2\measured{base},
>       %
>       columns=22,
>       columndistance=1pt,
>       %
>       grid=yes,
>     ]
>
>
> \showframe
> \showgrid
>
> \starttext
> \input tufte
> \stoptext
>
>
> Aditya
>