At 2024-12-04T00:08:23+0100, onf wrote: > On Tue Dec 3, 2024 at 11:56 PM CET, Tadziu Hoffmann wrote: > > I was thinking of something similar to > > > > .ne d Advance drawing position to the next vertical > > position trap and spring the trap, if it is > > nearer than distance d (default scaling unit v). [...] > > Reversing their order might make the intended meaning more obvious: > .ne d If the next vertical position trap is nearer than > distance d (default scaling unit v), advance drawing > position to it and spring it.
The phrase "and spring it" occurred to me as well. I think I'll go with
something much (exactly?) like this.
I might as well cross reference register .trunc while I'm there.
While we're on the subject, I was careful to say "vertical position
trap" instead of "page location trap", because `ne` interacts with
diversion traps as well.
I am sorely tempted to describe `ne` as "not a conditional `bp`, but a
conditional `sp`".
`sp` has a noteworthy limitation.
.sp dist Break and move the next text baseline down by dist, or
until springing a page location trap (default scaling
unit v). A negative dist will not reduce the position
of the text baseline below zero. Prefixing dist with
the | operator moves to a position relative to the page
top for positive N, and the bottom if N is negative; in
all cases, one line height (vee) is added to dist.
dist is ignored inside a diversion.
Check the final sentence. `ne` inherits this limitation. In a
diversion, you can ask `ne` for tons of space, but you'll only get 1v at
a time. Even if you invoke it more than once.
Input:
$ groff -ww <<EOF
.de trap
. tm BOING (.d=\\n[.d]u)
..
.di div
.tm JUST GOT STARTED (.d=\n[.d]u)
.dt 5v trap
.nf
1
.tm FIRST LINE OUT (.d=\n[.d]u)
2
.ne 3v
3
4
.tm ALMOST DONE (.d=\n[.d]u)
.ne
.tm JUST A BIT MORE (.d=\n[.d]u)
.ne
.tm I KEEP MASHING THIS THING BUT NOTHING HAPPENS (.d=\n[.d]u)
5
.tm DONE (.d=\n[.d]u)
.di
EOF
Output:
JUST GOT STARTED (.d=0u)
FIRST LINE OUT (.d=12000u)
ALMOST DONE (.d=48000u)
JUST A BIT MORE (.d=48000u)
I KEEP MASHING THIS THING BUT NOTHING HAPPENS (.d=48000u)
BOING (.d=-1u)
DONE (.d=60000u)
Regards,
Branden
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