Add horizontal splitting to TUI layout

This changes the TUI layout engine to add horizontal splitting.  Now,
windows can be side-by-side.

A horizontal split is defined using the "-horizontal" parameter to
"tui new-layout".

This also adds the first "winheight" test to the test suite.  One open
question is whether we want a new "winwidth" command, now that
horizontal layouts are possible.  This is easily done using the
generic layout code.

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

	PR tui/17850:
	* tui/tui-win.c (tui_gen_win_info::max_width): New method.
	* tui/tui-layout.h (class tui_layout_base) <get_sizes>: Add
	"height" argument.
	(class tui_layout_window) <get_sizes>: Likewise.
	(class tui_layout_split) <tui_layout_split>: Add "vertical"
	argument.
	<get_sizes>: Add "height" argument.
	<m_vertical>: New field.
	* tui/tui-layout.c (tui_layout_split::clone): Update.
	(tui_layout_split::get_sizes): Add "height" argument.
	(tui_layout_split::adjust_size, tui_layout_split::apply): Update.
	(tui_new_layout_command): Parse "-horizontal".
	(_initialize_tui_layout): Update help string.
	(tui_layout_split::specification): Add "-horizontal" when needed.
	* tui/tui-layout.c (tui_layout_window::get_sizes): Add "height"
	argument.
	* tui/tui-data.h (struct tui_gen_win_info) <max_width, min_width>:
	New methods.

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

	PR tui/17850:
	* gdb.texinfo (TUI Commands): Document horizontal layouts.

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

	PR tui/17850:
	* gdb.tui/new-layout.exp: Add horizontal layout and winheight
	tests.

Change-Id: I38b35e504f34698578af86686be03c0fefd954ae

2 files changed, 32 insertions, 4 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 99f2d93..2b6bbc8 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,5 +1,10 @@
 2020-02-22  Tom Tromey  <tom@tromey.com>
 
+	PR tui/17850:
+	* gdb.texinfo (TUI Commands): Document horizontal layouts.
+
+2020-02-22  Tom Tromey  <tom@tromey.com>
+
 	* gdb.texinfo (TUI Overview): Mention user layouts.
 	(TUI Commands): Document "tui new-layout".
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index c261738..0645fb0 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -27998,11 +27998,23 @@ List and give the size of all displayed windows.
 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
+Each @var{window} parameter is either the name of a window to display,
+or a window description.  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.
+window can be specified.  Note that, because it is of fixed height,
+the weight assigned to the status window is of no importance.  It is
+conventional to use @samp{0} here.
+
+A window description looks a bit like an invocation of @code{tui
+new-layout}, and is of the form
+@{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
+
+This specifies a sub-layout.  If @code{-horizontal} is given, the
+windows in this description will be arranged side-by-side, rather than
+top-to-bottom.
 
 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
@@ -28019,6 +28031,17 @@ 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.
 
+Here is a more complex example, showing a horizontal layout:
+
+@example
+(gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
+@end example
+
+This will result in side-by-side source and assembly windows; with the
+status and command window being beneath these, filling the entire
+width of the terminal.  Because they have weight 2, the source and
+assembly windows will be twice the height of the command window.
+
 @item layout @var{name}
 @kindex layout
 Changes which TUI windows are displayed.  The @var{name} parameter