[Emacs-diffs] /srv/bzr/emacs/trunk r106333: * doc/lispref/windows.texi (Splitting Windows): Simplify example.

[Chong Yidong]

------------------------------------------------------------
revno: 106333
committer: Chong Yidong <address@hidden>
branch nick: trunk
timestamp: Wed 2011-11-09 15:56:50 +0800
message:
  * doc/lispref/windows.texi (Splitting Windows): Simplify example.
modified:
  doc/lispref/ChangeLog
  doc/lispref/windows.texi

=== modified file 'doc/lispref/ChangeLog'
--- a/doc/lispref/ChangeLog     2011-11-08 15:34:21 +0000
+++ b/doc/lispref/ChangeLog     2011-11-09 07:56:50 +0000
@@ -1,3 +1,7 @@
+2011-11-09  Chong Yidong  <address@hidden>
+
+       * windows.texi (Splitting Windows): Simplify example.
+
 2011-11-08  Chong Yidong  <address@hidden>
 
        * windows.texi (Window Sizes): Copyedits.  Document

=== modified file 'doc/lispref/windows.texi'
--- a/doc/lispref/windows.texi  2011-11-08 15:34:21 +0000
+++ b/doc/lispref/windows.texi  2011-11-09 07:56:50 +0000
@@ -715,337 +715,131 @@
 @cindex splitting windows
 @cindex window splitting
 
-The functions described below are the primitives needed for creating a
-new window.  They do not accept a buffer as an argument.  Rather, they
-``split'' an existing window into two halves, both displaying the buffer
-previously visible in the window that was split.
+This section describes functions for creating a new window by
address@hidden an existing one.
 
 @deffn Command split-window &optional window size side
-This function creates a new window adjacent to @var{window}.  It returns
-the new window which is always a live window.  The argument @var{window}
-can denote any window and defaults to the selected one.  This function
-does not change the selected window.
-
-Optional second argument @var{size} a positive number means make
address@hidden @var{size} lines (or columns) tall.  If @var{size} is
-negative, make the new window @address@hidden lines (or columns)
-tall.  If @var{size} is omitted or @code{nil}, then @var{window} is
-divided evenly into two parts.  (If there is an odd line, it is
-allocated to the new window.)
-
-Normally, the customizable variables @code{window-min-height} and
address@hidden specify the smallest allowable size of a
-window.  @xref{Change Window,,Deleting and Rearranging Windows, emacs,
-The GNU Emacs Manual}.  If splitting would result in making a window
-smaller than this, this function usually signals an error.  However,
-if @var{size} is address@hidden and valid, a new window of the
-requested size is created, provided it has enough space for a text
-area one line tall and/or two columns wide.
-
-Optional third argument @var{side} @code{nil} (or @code{below})
-specifies that the new window shall be located below @var{window}.  The
-value @code{above} means the new window will be located above
address@hidden  In both cases @var{size} specifies the new number of
-lines for @var{window} (or the new window if @var{size} is negative)
-including space reserved for the mode and/or header line.
-
-If @var{side} is @code{t} or @code{right} the new window will be
-positioned on the right side of @var{window}.  The value @code{left}
-means the new window will be located on the left side of @var{window}.
-In both cases @var{size} specifies the new number of columns for
address@hidden (or the new window provided @var{size} is negative)
-including space reserved for margins, fringes and the scroll bar or a
-divider column.
-
-Any other address@hidden value for @var{side} is currently handled like
address@hidden (or @code{right}).  Since this might change in the future,
-application programs should refrain from using other values.
-
-If @var{window} is live, properties of the new window like margins and
-scroll bars are inherited from @var{window}.  If @var{window} is an
-internal window, these properties, as well as the buffer shown in the
-new window, are inherited from the window selected on @var{window}'s
-frame.
-
-If @code{ignore-window-parameters} is address@hidden, this function
-ignores window parameters (@pxref{Window Parameters}).  Otherwise, if
-the @code{split-window} parameter of @var{window} is @code{t}, it splits
-the window disregarding any other window parameters.  If the
address@hidden parameter specifies a function, that function is
-called with the arguments @var{window}, @var{size}, and @var{side} to
-split @var{window}.  If that function is @code{ignore}, nothing is done.
+This function creates a new live window next to the window
address@hidden  If @var{window} is omitted or @code{nil}, it defaults
+to the selected window.  That window is ``split'', and reduced in
+size.  The space is taken up by the new window, which is returned.
+
+The optional second argument @var{size} determines the sizes of the
address@hidden and/or the new window.  If it is omitted or @code{nil},
+both windows are given equal sizes; if there is an odd line, it is
+allocated to the new window.  If @var{size} is a positive number,
address@hidden is given @var{size} lines (or columns, depending on the
+value of @var{side}).  If @var{size} is a negative number, the new
+window is given @address@hidden lines (or columns).
+
+If @var{size} is @code{nil}, this function obeys the variables
address@hidden and @code{window-min-width}.  @xref{Change
+Window,,Deleting and Rearranging Windows, emacs, The GNU Emacs
+Manual}.  Thus, it signals an error if splitting would result in
+making a window smaller than those variables specify.  However, a
address@hidden value for @var{size} causes those variables to be
+ignored; in that case, the smallest allowable window is considered to
+be one that has space for a text area one line tall and/or two columns
+wide.
+
+The optional third argument @var{side} determines the position of the
+new window relative to @var{window}.  If it is @code{nil} or
address@hidden, the new window is placed below @var{window}.  If it is
address@hidden, the new window is placed above @var{window}.  In both
+these cases, @var{size} specifies a total window height, in lines.
+
+If @var{side} is @code{t} or @code{right}, the new window is placed on
+the right of @var{window}.  If @var{side} is @code{left}, the new
+window is placed on the left of @var{window}.  In both these cases,
address@hidden specifies a total window width, in columns.
+
+If @var{window} is a live window, the new window inherits various
+properties from it, including margins and scroll bars.  If
address@hidden is an internal window, the new window inherits the
+properties of the window selected within @var{window}'s frame.
+
+If the variable @code{ignore-window-parameters} is address@hidden
+(@pxref{Window Parameters}), this function ignores window parameters.
+Otherwise, it consults the @code{split-window} parameter of
address@hidden; if this is @code{t}, it splits the window disregarding
+any other window parameters.  If the @code{split-window} parameter
+specifies a function, that function is called with the arguments
address@hidden, @var{size}, and @var{side} to split @var{window}, in
+lieu of the usual action of @code{split-window}.
 @end deffn
 
-The following example starts with one window on a screen that is 50
-lines high by 80 columns wide; then it splits the window.
-
address@hidden
address@hidden
-(setq W1 (selected-window))
-     @result{} #<window 8 on windows.texi>
-(setq W2 (split-window W1 15))
-     @result{} #<window 28 on windows.texi>
address@hidden group
address@hidden
-(window-top-line W1)
-     @result{} 0
-(window-total-size W1)
-     @result{} 15
-(window-top-line W2)
-     @result{} 15
address@hidden group
address@hidden smallexample
-
-The screen looks like this:
-
address@hidden
address@hidden
-         __________
-        |          |  line 0
-        |    W1    |
-        |__________|
-        |          |  line 15
-        |    W2    |
-        |__________|
-                      line 50
- column 0   column 80
address@hidden group
address@hidden smallexample
-
-Next, split the top window into two side-by-side windows:
-
address@hidden
address@hidden
-(setq W3 (split-window W1 35 t))
-     @result{} #<window 32 on windows.texi>
address@hidden group
address@hidden
-(window-left-column W1)
-     @result{} 0
-(window-total-size W1 t)
-     @result{} 35
-(window-left-column W3)
-     @result{} 35
address@hidden group
address@hidden smallexample
-
address@hidden 3000
-Now the screen looks like this:
-
address@hidden
address@hidden
-     column 35
-         __________
-        |    |     |  line 0
-        | W1 |  W3 |
-        |____|_____|
-        |          |  line 15
-        |    W2    |
-        |__________|
-                      line 50
- column 0   column 80
address@hidden group
address@hidden smallexample
-
-Normally, Emacs indicates the border between two side-by-side windows
-with a scroll bar (@pxref{Scroll Bars}), or with @samp{|} characters.  The
-display table can specify alternative border characters; see @ref{Display
-Tables}.
-
-Below we describe how @code{split-window} can be used to create the
-window configuration from our earlier example (@pxref{Windows and
-Frames}) and how internal windows are created for this purpose.  We
-start with a frame containing one live window @code{W2} (in the
-following scenarios window names are assigned in an arbitrary manner in
-order to match the names of the example).  Evaluating the form
address@hidden(split-window W2 8 t)} creates a new internal window @code{W1}
-with two address@hidden (the window we've split) and a new leaf
-window @code{W6}:
address@hidden
address@hidden
-     ______________________________________
-    | ______  ____________________________ |
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||      ||                            ||
-    ||__W2__||_____________W6_____________ |
-    |__________________W1__________________|
-
address@hidden group
address@hidden smallexample
-
-Evaluating now @code{(split-window W6 -3)} creates another internal
-window @code{W3} with two address@hidden and a new live window
address@hidden  This leaves us with a vertically combined window @code{W3}
-embedded in the horizontally combined window @code{W1}:
address@hidden
address@hidden
-     ______________________________________
-    | ______  ____________________________ |
-    ||      || __________________________ ||
-    ||      |||                          |||
-    ||      |||                          |||
-    ||      |||                          |||
-    ||      |||                          |||
-    ||      |||                          |||
-    ||      |||____________W6____________|||
-    ||      || __________________________ ||
-    ||      |||                          |||
-    ||      |||____________W5____________|||
-    ||__W2__||_____________W3_____________ |
-    |__________________W1__________________|
-
address@hidden group
address@hidden smallexample
-
-Finally, evaluating @code{(split-window W6 nil t)} should get us the
-desired configuration as depicted below.
address@hidden
address@hidden
-     ______________________________________
-    | ______  ____________________________ |
-    ||      || __________________________ ||
-    ||      ||| ___________  ___________ |||
-    ||      ||||           ||           ||||
-    ||      ||||           ||           ||||
-    ||      ||||_____W6____||_____W7____||||
+  As an example, we show a combination of @code{split-window} calls
+that yields the window configuration discussed in @ref{Windows and
+Frames}.  This example demonstrates splitting live windows as well as
+splitting internal windows.  We begin with a frame containing a single
+window (a live root window), which we denote by @var{W4}.  Calling
address@hidden(split-window W3)} yields this window configuration:
+
address@hidden
address@hidden
+     ______________________________________
+    | ____________________________________ |
+    ||                                    ||
+    ||                                    ||
+    ||                                    ||
+    ||_________________W4_________________||
+    | ____________________________________ |
+    ||                                    ||
+    ||                                    ||
+    ||                                    ||
+    ||_________________W5_________________||
+    |__________________W3__________________|
+
address@hidden group
address@hidden smallexample
+
address@hidden
+The @code{split-window} call has created a new live window, denoted by
address@hidden  It has also created a new internal window, denoted by
address@hidden, which becomes the root window and the parent of both
address@hidden and @var{W5}.
+
+  Next, we call @code{(split-window W3 nil 'left)}, passing the
+internal window @var{W3} as the argument.  The result:
+
address@hidden
address@hidden
+     ______________________________________
+    | ______  ____________________________ |
+    ||      || __________________________ ||
+    ||      |||                          |||
+    ||      |||                          |||
+    ||      |||                          |||
     ||      |||____________W4____________|||
     ||      || __________________________ ||
     ||      |||                          |||
+    ||      |||                          |||
     ||      |||____________W5____________|||
     ||__W2__||_____________W3_____________ |
     |__________________W1__________________|
-
address@hidden group
address@hidden smallexample
-
-The scenario sketched above is the standard way to obtain the desired
-configuration.  In Emacs 23 it was also the only way to do that since
-Emacs 23 didn't allow splitting internal windows.
-
-With Emacs 24 you can also proceed as follows: Split an initial window
address@hidden by evaluating @code{(split-window W6 -3)} to produce the
-following vertical combination:
address@hidden
address@hidden
-     ______________________________________
-    | ____________________________________ |
-    ||                                    ||
-    ||                                    ||
-    ||                                    ||
-    ||                                    ||
-    ||                                    ||
-    ||                                    ||
-    ||                                    ||
-    ||_________________W6_________________||
-    | ____________________________________ |
-    ||                                    ||
-    ||_________________W5_________________||
-    |__________________W3__________________|
-
address@hidden group
address@hidden smallexample
-
-Evaluating now @code{(split-window (window-parent W6) -8 'left)} or,
-equivalently, @code{(split-window W3 -8 'left)} should now produce the
-penultimate configuration from the previous scenario from where we can
-continue as described before.
-
-   Another strategy starts with splitting an initial window @code{W6} by
-evaluating @code{(split-window W6 nil nil t)} with the following result:
address@hidden
address@hidden
-     ______________________________________
-    | _________________  _________________ |
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||                 ||                 ||
-    ||________W6_______||________W7_______||
-    |__________________W4__________________|
-
address@hidden group
address@hidden smallexample
-
-Evaluating now @code{(split-window W4 -3)} or @code{(split-window
-(window-parent W6) -3)} should get us a configuration as shown next.
address@hidden
address@hidden
-     ______________________________________
-    | ____________________________________ |
-    || ________________  ________________ ||
-    |||                ||                |||
-    |||                ||                |||
-    |||                ||                |||
-    |||                ||                |||
-    |||                ||                |||
-    |||_______W6_______||________W7______|||
-    ||_________________W4_________________||
-    | ____________________________________ |
-    ||                                    ||
-    ||_________________W5_________________||
-    |__________________W3__________________|
-
address@hidden group
address@hidden smallexample
-
-The desired configuration can be now obtained by evaluating
address@hidden(split-window W3 -8 'left)} or, equivalently, @code{(split-window
-(window-parent W5) -8 'left)}.
-
-   For a final approach let's start with the configuration of two live
-windows @code{W6} and @code{W7} shown above.  If we now evaluate
address@hidden(split-window W4 -8 'left)} or @code{(split-window (window-parent
-W6) -8 'left)} we get the following configuration.
address@hidden
address@hidden
-     ______________________________________
-    | ______  ____________________________ |
-    ||      || ____________  ____________ ||
-    ||      |||            ||            |||
-    ||      |||            ||            |||
-    ||      |||            ||            |||
-    ||      |||            ||            |||
-    ||      |||            ||            |||
-    ||      |||            ||            |||
-    ||      |||            ||            |||
-    ||      |||______W6____||______W7____|||
-    ||__W2__||_____________W4_____________||
-    |__________________W1__________________|
-
address@hidden group
address@hidden smallexample
-
-Evaluating now @code{(split-window W4 -3)} or, for example,
address@hidden(split-window (window-parent W6) -3)} should produce the desired
-configuration.
-
-  The two options described next can be used to tune the operation of
address@hidden group
address@hidden smallexample
+
address@hidden
+A new live window, @var{W2}, is created to the left of @var{W3} (which
+encompasses the vertical window combination of @var{W4} and @var{W5}).
+A new internal window @var{W1} is also created, and becomes the new
+root window.
+
+  The following two options can be used to modify the operation of
 @code{split-window}.
 
 @defopt window-splits
-If this variable is @code{nil}, the function @code{split-window} can
-split a window if and only if that window's screen estate is
-sufficiently large to accommodate both--itself and the new window.
+If this variable is @code{nil}, @code{split-window} can only split a
+window (denoted by @var{window}) if @var{window}'s screen area is
+large enough to accommodate both itself and the new window.  This is
+the default.
 
-If this variable is address@hidden, @code{split-window} tries to resize
-all windows that are part of the same combination as the old window to
-accommodate the new window.  Hence, the new window can be also created if
-the old window is of fixed size or too small to split (@pxref{Window
-Sizes}).
+If this variable is address@hidden, @code{split-window} tries to
+resize all windows that are part of the same combination as
address@hidden, in order to accommodate the new window.  In particular,
+this may allow @code{split-window} to succeed even if @var{window} is
+a fixed-size window or too small to ordinarily split.
 
 In any case, the value of this variable is assigned to the splits status
 of the new window and, provided old and new window form a new