Add the "tui new-layout" command

This adds a new command, "tui new-layout".  This command can be used
to define a new TUI window layout.

The command is used like:

(gdb) tui new-layout name src 1 regs 1 status 0 cmd 1

The first argument is the name of the layout.  In this example, it is
"name", so the new layout could be seen by "layout name".

Subsequent arguments come in pairs, where the first item in a pair is
the name of a window, and the second item in a pair is the window's
weight.  A weight is just an integer -- a window's allocated size is
proportional to the total of the weights given.  So, in the above
example, all windows will have the same size (the status windows's
weight does not matter, because it has fixed height).

gdb/ChangeLog
2020-02-22  Tom Tromey  <tom@tromey.com>

	* NEWS: Add "tui new-layout" item.
	* tui/tui-layout.c (add_layout_command): Return cmd_list_element.
	Add new-layout command to help text.
	(validate_window_name): New function.
	(tui_new_layout_command): New function.
	(_initialize_tui_layout): Register "new-layout".
	(tui_layout_window::specification): New method.
	(tui_layout_window::specification): New method.
	* tui/tui-layout.h (class tui_layout_base) <specification>: New
	method.
	(class tui_layout_window) <specification>: New method.
	(class tui_layout_split) <specification>: New method.

gdb/doc/ChangeLog
2020-02-22  Tom Tromey  <tom@tromey.com>

	* gdb.texinfo (TUI Overview): Mention user layouts.
	(TUI Commands): Document "tui new-layout".

gdb/testsuite/ChangeLog
2020-02-22  Tom Tromey  <tom@tromey.com>

	* gdb.tui/new-layout.exp: New file.

Change-Id: Id7c3ace20ab1e8924f8f4ad788f40210f58a5c05

2 files changed, 39 insertions, 3 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 4900480..99f2d93 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,8 @@
+2020-02-22  Tom Tromey  <tom@tromey.com>
+
+	* gdb.texinfo (TUI Overview): Mention user layouts.
+	(TUI Commands): Document "tui new-layout".
+
 2020-01-26  Tom Tromey  <tromey@adacore.com>
 
 	* gdb.texinfo (M68K Features): Document floating-point feature
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index a2866a2..c261738 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -27755,6 +27755,8 @@ source and registers, or
 assembly and registers.
 @end itemize
 
+These are the standard layouts, but other layouts can be defined.
+
 A status line above the command window shows the following information:
 
 @table @emph
@@ -27991,11 +27993,40 @@ Disable TUI mode, returning to the console interpreter.
 @kindex info win
 List and give the size of all displayed windows.
 
+@item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
+@kindex tui new-layout
+Create a new TUI layout.  The new layout will be named @var{name}, and
+can be accessed using the @code{layout} command (see below).
+
+Each @var{window} parameter is the name of a window to display.  The
+windows will be displayed from top to bottom in the order listed.  The
+names of the windows are the same as the ones given to the
+@code{focus} command (see below); additional, the @code{status}
+window can be specified.
+
+Each @var{weight} is an integer.  It is the weight of this window
+relative to all the other windows in the layout.  These numbers are
+used to calculate how much of the screen is given to each window.
+
+For example:
+
+@example
+(gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
+@end example
+
+Here, the new layout is called @samp{example}.  It shows the source
+and register windows, followed by the status window, and then finally
+the command window.  The non-status windows all have the same weight,
+so the terminal will be split into three roughly equal sections.
+
 @item layout @var{name}
 @kindex layout
-Changes which TUI windows are displayed.  In each layout the command
-window is always displayed, the @var{name} parameter controls which
-additional windows are displayed, and can be any of the following:
+Changes which TUI windows are displayed.  The @var{name} parameter
+controls which layout is shown.  It can be either one of the built-in
+layout names, or the name of a layout defined by the user using
+@code{tui new-layout}.
+
+The built-in layouts are as follows:
 
 @table @code
 @item next