Add documentation for horizontal scroll bars and fix some minor issues.

* buffer.c (scroll_bar_width, scroll_bar_height): Fix
doc-strings.
* window.c (Fset_window_scroll_bars): Fix doc-string.
(Fwindow_scroll_bars): Have it return what the doc-string says.

* window.el (window-full-height-p): Make it behave correctly for
minibuffer window.
(window-current-scroll-bars): Fix code.
(fit-frame-to-buffer): Use window-scroll-bar-height instead of
window-scroll-bars.
* frame.el (frame-current-scroll-bars): Fix doc-string.
* scroll-bar.el (toggle-horizontal-scroll-bar): New command.

* frames.texi (Scroll Bars): Describe use of horizontal scroll
bars.

* display.texi (Scroll Bars): Add description of horizontal scroll
bars and associated functions.
* frames.texi (Layout Parameters): Add horizontal scroll bar
entries.  Remove paragraph on "combined fringe widths".
* windows.texi (Window Sizes): Describe affects of horizontal
scroll bars on window layout and sizes.  Fix description of
window-full-height-p.
(Resizing Windows): Mention horizontal scroll bar.

1 files changed, 7 insertions, 13 deletions

diff --git a/doc/lispref/frames.texi b/doc/lispref/frames.texi
index c8e0fff6cd0..464c5fccc4f 100644
--- a/doc/lispref/frames.texi
+++ b/doc/lispref/frames.texi
@@ -709,19 +709,21 @@ Whether the frame has scroll bars for vertical scrolling, and which side
 of the frame they should be on.  The possible values are @code{left},
 @code{right}, and @code{nil} for no scroll bars.
 
-@ignore
 @vindex horizontal-scroll-bars, a frame parameter
 @item horizontal-scroll-bars
-Whether the frame has scroll bars for horizontal scrolling
-(non-@code{nil} means yes).  Horizontal scroll bars are not currently
-implemented.
-@end ignore
+Whether the frame has scroll bars for horizontal scrolling (@code{t} and
+@code{bottom} mean yes, @code{nil} means no).
 
 @vindex scroll-bar-width, a frame parameter
 @item scroll-bar-width
 The width of vertical scroll bars, in pixels, or @code{nil} meaning to
 use the default width.
 
+@vindex scroll-bar-height, a frame parameter
+@item scroll-bar-height
+The height of horizontal scroll bars, in pixels, or @code{nil} meaning
+to use the default height.
+
 @vindex left-fringe, a frame parameter
 @vindex right-fringe, a frame parameter
 @item left-fringe
@@ -735,14 +737,6 @@ these two frame parameters, the return value is always an integer.
 When using @code{set-frame-parameter}, passing a @code{nil} value
 imposes an actual default value of 8 pixels.
 
-The combined fringe widths must add up to an integral number of
-columns, so the actual default fringe widths for the frame, as
-reported by @code{frame-parameter}, may be larger than what you
-specify.  Any extra width is distributed evenly between the left and
-right fringe.  However, you can force one fringe or the other to a
-precise width by specifying that width as a negative integer.  If both
-widths are negative, only the left fringe gets the specified width.
-
 @vindex right-divider-width, a frame parameter
 @item right-divider-width
 The width (thickness) reserved for the right divider (@pxref{Window