1 files changed, 12 insertions, 6 deletions

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 3c3ee1fc6a4..fd6820897f3 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -5446,12 +5446,14 @@ because omitting them is what indicates the data has the format of an
 XBM file.  The file contents specify the height and width of the image.
 
 @item
-A string or a bool-vector containing the bits of the image (plus perhaps
-some extra bits at the end that will not be used).  It should contain at
-least @var{width} * @code{height} bits.  In this case, you must specify
-@code{:height} and @code{:width}, both to indicate that the string
-contains just the bits rather than a whole XBM file, and to specify the
-size of the image.
+A string or a bool-vector containing the bits of the image (plus
+perhaps some extra bits at the end that will not be used).  It should
+contain at least @w{@code{@var{stride} * @var{height}}} bits, where
+@var{stride} is the smallest multiple of 8 greater than or equal to
+the width of the image.  In this case, you should specify
+@code{:height}, @code{:width} and @code{:stride}, both to indicate
+that the string contains just the bits rather than a whole XBM file,
+and to specify the size of the image.
 @end itemize
 
 @item :width @var{width}
@@ -5459,6 +5461,10 @@ The value, @var{width}, specifies the width of the image, in pixels.
 
 @item :height @var{height}
 The value, @var{height}, specifies the height of the image, in pixels.
+
+@item :stride @var{stride}
+The number of bool vector entries stored for each row; the smallest
+multiple of 8 greater than or equal to @var{width}.
 @end table
 
 @node XPM Images