On 2014-06-02 04:09, Hans Hagen wrote:
> On 6/2/2014 3:44 AM, Rik Kabel wrote:
>> On 2014-06-01 12:52, Hans Hagen wrote:
>>> On 6/1/2014 5:40 PM, Rik wrote:
>>>
>>>> Is this also the cause of problems I noted with heading placed into 
>>>> the
>>>> margin, as in the example below?
>>>
>>> no, unrelated, try this:
>>>
>>> \setuphead
>>>   [section]
>>>   [after={\strut\blank[-2*line,samepage,disable]},
>>>    command=\SectionCommand,
>>>    distance=0pt]
>>>
>>> \define[2]\SectionCommand{\inleft{XXXXXX}}
>>
>> That was fine until it ran into \setupwhitespace with a non-zero value.
>> Fiddling with the after key \blank does not appear to help.
>>
>>     \define[2]\MarginHead{\inmargin{#1\\#2}}
>>     \setuphead    [section]
>>                    [command=\MarginHead,
>>                     distance=0pt,
>> after={\strut\blank[-2*line,samepage,disable]}]
>>     %% With no \setupwhitespace, or any \setupwhitespace setting that
>>     %%   results in zero interparagraph whitespace, all is well.
>>     %setupwhitespace      [none]%    okay
>>     %setupwhitespace      [fix]%     okay
>>     %% With non-zero interparagraph whitespace, the heading separates
>>     %%   from the text
>>     \setupwhitespace      [line]%    bad
>>     \starttext
>>     \startchapter[title={Weisman}]
>>       \input weisman\par
>>       \input weisman
>>     \startsection[title={Thuan}]
>>       \input thuan\par
>>       \input thuan
>>     \stopsection
>>     \stopchapter
>>     \stoptext
>
> you can always skip back whitespace or add 'nowhite'

Well, nowhite is a start, but the solution is still a way off. 
Meanwhile, the following works for non-grid layouts with reasonable 
values for \setupwhitespace, although perhaps somebody can come up with 
a more eloquent way to write it:

    \newdimen\SectionHeadSkip
    \SectionHeadSkip\dimexpr-2\lineheight-\parskip\relax
    \setuphead
       [section]
       [command=\SectionCommand,
        distance=0pt,
        after={\strut\blank[\the\SectionHeadSkip,samepage,disable,nowhite]},
       ]
      \define[2]\SectionCommand
        {\inmargin{#1 -- #2}}

When enabling grid layouts, the number of lines needs to be adjusted.

Floats that appear as the first thing after a heading may present 
problems, especially with larger values for \setupwhitespace. (The 
default, with no location= specified, is pretty good, but when 
location={left,force} or such, there is often an unwanted offset from 
the header. and page breaks still appear between the heading and figure 
at times, despite the samepage setting for \blank.)

So, this is quite fragile. It requires careful checking of every 
heading, and manual tuning when one breaks. Not a desirable solution, 
but at least it is possible.

-- 
Rik Kabel