From 52fd40068e0f8b41bd29eaec1334299eb86d0bff Mon Sep 17 00:00:00 2001 From: Eli Zaretskii Date: Mon, 4 Mar 2019 19:49:47 +0200 Subject: [PATCH] Minor improvement of documentation of '(when CONDITION . SPEC)' * doc/lispref/display.texi (Other Display Specs): Add a caveat to using the '(when CONDITION . SPEC)' display specs. --- doc/lispref/display.texi | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi index 921d58a1f3a..7892c15b462 100644 --- a/doc/lispref/display.texi +++ b/doc/lispref/display.texi @@ -4853,6 +4853,16 @@ and the buffer position where the @code{display} property was found, respectively. Both positions can be different when @code{object} is a string. +Note that @var{condition} will only be evaluated when redisplay +examines the text where this display spec is located, so this feature +is best suited for conditions that are relatively stable, i.e.@: +yield, for each particular buffer position, the same results on every +evaluation. If the results change for the same text location, e.g., +if the result depends on the position of point, then the conditional +specification might not do what you want, because redisplay examines +only those parts of buffer text where it has reasons to assume that +something changed since the last display cycle. + @node Display Margins @subsection Displaying in the Margins @cindex display margins -- 2.39.2