Pawel Urbanski via ntg-context schrieb am 21.05.2023 um 20:39:
> Hi,
>
> Using the 'backspace' key worked for setting up equal margins for my 
> downloadable version.
>
> I created a mode for printing where I used the following values:
>
> \setuplayout[
>
>     rightmargin=52pt, leftmargin=52pt,
>
>     backspace=16pt, ...]
>
> Unfortunately the text width is not equal to 312pt as in hte 
> downloadable version.
>
> I used these values since I infered that we have:
>
> ** left and righ margins on the sides of text,
>
> ** backspace which is an additional space in the gutter.
>
> Following the setup I described in the printable version I would get 
> or I at least wanted:
>
> 52pt outer margins and 68pt inner margins.
>
>
> Is my reasoning correct or I am missing something?

The leftmargin and rightmargin keys have no relation to the left and 
margins of the text block.

What you have to do is to set values to the backspace and cutspace keys.

In the example below you can switch between the layout of the print and 
screen version by changing modes.

\enablemode[print]
%\enablemode[screen]

\definepapersize [pawel] [width=432pt,height=648pt]

\setuppapersize [pawel]

\startmode[print]
\setuplayout
   [backspace=52pt,
     cutspace=68pt,
        width=middle]
\stopmode

\startmode[screen]
\setuplayout
   [backspace=60pt,
        width=312pt]
\stopmode

\starttext
\showlayout
\stoptext

Wolfgang