From: Dani Moncayo Date: Sun, 18 Nov 2012 06:27:43 +0000 (+0800) Subject: Emacs manual fixes regarding automatic scrolling. X-Git-Tag: emacs-24.2.90~42 X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=d1a355a1bfb2ff5914e42267c2d0c9e414f08b68;p=emacs.git Emacs manual fixes regarding automatic scrolling. * display.texi (Auto Scrolling): Fix some inaccuracies, plus clarifications. (Horizontal Scrolling): Clarifications. Fixes: debbugs:12865 --- diff --git a/doc/emacs/ChangeLog b/doc/emacs/ChangeLog index 5f8a252b5d6..56001d6e29e 100644 --- a/doc/emacs/ChangeLog +++ b/doc/emacs/ChangeLog @@ -1,3 +1,9 @@ +2012-11-18 Dani Moncayo + + * display.texi (Auto Scrolling): Fix some inaccuracies, plus + clarifications (Bug#12865). + (Horizontal Scrolling): Clarifications. + 2012-11-17 Dani Moncayo * mark.texi (Disabled Transient Mark): Doc fixes (Bug#12746). diff --git a/doc/emacs/display.texi b/doc/emacs/display.texi index b6ab4913f9c..876c46bdf1a 100644 --- a/doc/emacs/display.texi +++ b/doc/emacs/display.texi @@ -213,59 +213,62 @@ entire current defun onto the screen if possible. @node Auto Scrolling @section Automatic Scrolling +@cindex automatic scrolling Emacs performs @dfn{automatic scrolling} when point moves out of the -visible portion of the text. +visible portion of the text. Normally, automatic scrolling centers +point vertically in the window, but there are several ways to alter +this behavior. @vindex scroll-conservatively - Normally, this centers point vertically within the window. However, -if you set @code{scroll-conservatively} to a small number @var{n}, -then if you move point just a little off the screen (less than @var{n} -lines), Emacs scrolls the text just far enough to bring point back on -screen. If doing so fails to make point visible, Emacs centers point -in the window. By default, @code{scroll-conservatively} is@tie{}0. -If you set @code{scroll-conservatively} to a large number (larger than -100), Emacs will never center point as result of scrolling, even if -point moves far away from the text previously displayed in the window. -With such a large value, Emacs will always scroll text just enough for -bringing point into view, so point will end up at the top or bottom of -the window, depending on the scroll direction. + If you set @code{scroll-conservatively} to a small number @var{n}, +then moving point just a little off the screen (no more than @var{n} +lines) causes Emacs to scroll just enough to bring point back on +screen; if doing so fails to make point visible, Emacs scrolls just +far enough to center point in the window. If you set +@code{scroll-conservatively} to a large number (larger than 100), +automatic scrolling never centers point, no matter how far point +moves; Emacs always scrolls text just enough to bring point into view, +either at the top or bottom of the window depending on the scroll +direction. By default, @code{scroll-conservatively} is@tie{}0, which +means to always center point in the window. @vindex scroll-step - An alternative way of controlling how Emacs scrolls text is by -customizing the variable @code{scroll-step}. Its value determines how -many lines to scroll the window when point moves off the screen. If -moving by that number of lines fails to bring point back into view, -point is centered instead. The default value is zero, which causes -point to always be centered after scrolling. - - Since both @code{scroll-conservatively} and @code{scroll-step} -control automatic scrolling in contradicting ways, you should set only -one of them. If you customize both, the value of -@code{scroll-conservatively} takes precedence. + Another way to control automatic scrolling is to customize the +variable @code{scroll-step}. Its value determines the number of lines +by which to automatically scroll, when point moves off the screen. If +scrolling by that number of lines fails to bring point back into view, +point is centered instead. The default value is zero, which (by +default) causes point to always be centered after scrolling. @cindex aggressive scrolling @vindex scroll-up-aggressively @vindex scroll-down-aggressively - When the window does scroll by a distance longer than -@code{scroll-step}, you can control how aggressively it scrolls by -setting the variables @code{scroll-up-aggressively} and -@code{scroll-down-aggressively}. The value of -@code{scroll-up-aggressively} should be either @code{nil}, or a -fraction @var{f} between 0 and 1. A fraction specifies where on the -screen to put point when scrolling upward, i.e.@: forward. When point -goes off the window end, the new start position is chosen to put point -@var{f} parts of the window height from the bottom margin. Thus, -larger @var{f} means more aggressive scrolling: more new text is -brought into view. The default value, @code{nil}, is equivalent to -0.5. - - Likewise, @code{scroll-down-aggressively} is used for scrolling -down, i.e.@: backward. The value specifies how far point should be -placed from the top margin of the window; thus, as with -@code{scroll-up-aggressively}, a larger value is more aggressive. - - These two variables are ignored if either @code{scroll-step} or -@code{scroll-conservatively} are set to a non-zero value. + A third way to control automatic scrolling is to customize the +variables @code{scroll-up-aggressively} and +@code{scroll-down-aggressively}, which directly specify the vertical +position of point after scrolling. The value of +@code{scroll-up-aggressively} should be either @code{nil} (the +default), or a floating point number @var{f} between 0 and 1. The +latter means that when point goes below the bottom window edge (i.e.@: +scrolling forward), Emacs scrolls the window so that point is @var{f} +parts of the window height from the bottom window edge. Thus, larger +@var{f} means more aggressive scrolling: more new text is brought into +view. The default value, @code{nil}, is equivalent to 0.5. + + Likewise, @code{scroll-down-aggressively} is used when point goes +above the bottom window edge (i.e.@: scrolling backward). The value +specifies how far point should be from the top margin of the window +after scrolling. Thus, as with @code{scroll-up-aggressively}, a +larger value is more aggressive. + + Note that the variables @code{scroll-conservatively}, +@code{scroll-step}, and @code{scroll-up-aggressively} / +@code{scroll-down-aggressively} control automatic scrolling in +contradictory ways. Therefore, you should pick no more than one of +these methods to customize automatic scrolling. In case you customize +multiple variables, the order of priority is: +@code{scroll-conservatively}, then @code{scroll-step}, and finally +@code{scroll-up-aggressively} / @code{scroll-down-aggressively}. @vindex scroll-margin The variable @code{scroll-margin} restricts how close point can come @@ -295,10 +298,10 @@ the cursor is left at the edge instead.) @vindex hscroll-margin The variable @code{hscroll-margin} controls how close point can get -to the window's edges before automatic scrolling occurs. It is -measured in columns. For example, if the value is 5, then moving -point within 5 columns of an edge causes horizontal scrolling away -from that edge. +to the window's left and right edges before automatic scrolling +occurs. It is measured in columns. For example, if the value is 5, +then moving point within 5 columns of an edge causes horizontal +scrolling away from that edge. @vindex hscroll-step The variable @code{hscroll-step} determines how many columns to