faces.
@item :extend
-Whether or not this face will be extended until the end of the window.
-The value should be @code{t} to extend until end of the window using
-this face or @code{nil} fill the space between the end of the line and
-the end of the window with the default face. When a face is conformed
-by merging multiple other faces; only those with @code{:extend t} will
-be merged to conform a new face to extend until end of window. By
-default only @code{region} and @code{hl-line} have this attribute set
-to @code{t}.
+Whether or not this face will be extended beyond end of line and will
+affect the display of the empty space between the end of line and the
+edge of the window. The value should be @code{t} to display the empty
+space between end of line and edge of the window using this face, or
+@code{nil} to not use this face for the space between the end of the
+line and the edge of the window. When Emacs merges several faces for
+displaying the empty space beyond end of line, only those faces with
+@code{:extend} non-@code{nil} will be merged. By default, only
+@code{region} and @code{hl-line} faces have this attribute set to
+@code{t}.
@end table
+++
** New face attribute ':extend' to control face extension at EOL.
-There is a new face attribute :extend to use the face attributes to
-extend after the end of the line until the end of the window. Such
-:extend is set to nil by default in all faces except for 'hl-line' and
-'region' because those extend until the end of the window by default.
+The new face attribute ':extend' controls whether to use the face for
+displaying the empty space beyond end of line (EOL) till the edge of
+the window. By default, this attribute is non-nil only for 'region'
+and 'hl-line' faces; any other face that crosses end of line will not
+affect the display of the empty space at EOL.
** Connection-local variables