A surprising interaction

A surprising interaction

[Nigel King]

Dear ConTeXtnicians,

I have found a problem constructing my front and back cover for a user
manual. In the program below I use the setupexternalfigures line below
setting the maximum horizontal and vertical size in in order to simplify the
inclusion of figures. It has the undesired side effect of reducing the size
of the front and back cover.

In the program below the first page of the document is smaller than the
subsequent page.

\showframe
\setupexternalfigures
    [maxwidth=\textwidth,maxheight=0.8\textheight]
\starttext
\startMPpage
    StartPage;
    fill Page withcolor 0.5white;
    StopPage;
\stopMPpage
\input tufte
\stoptext

Clearly I can set this line after the first page. Presumably I need to set
the line to \pagewidth and \pageheight before the back cover. A further
surprise is that the body page background does not seem to be effected.

\startuseMPgraphic{bg}
    StartPage;
    fill Page withcolor 0.5white;
    StopPage;
\stopuseMPgraphic
\defineoverlay[page][\useMPgraphic{bg}]
\setupbackgrounds[page][background=page]

regards
-- 
Nigel