Introduce "struct ui"

This is a step towards supporting multiple consoles/MIs, each on its
own stdio streams / terminal.

See intro comment in top.h.

(I've had trouble picking a name for this object.  I've started out
with "struct console" originally.  But then this is about MI as well,
and there's "interpreter-exec console", which is specifically about
the CLI...

So I changed to "struct terminal", but, then we have a terminal object
that works when the input is not a terminal as well ...

Then I sort of gave up and renamed it to "struct top_level".  But it
then gets horribly confusing when we talk about the "top level
interpreter that's running on the current top level".

In the end, I realized we're already sort of calling this "ui", in
struct ui_out, struct ui_file, and a few coments here and there.)

gdb/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* event-top.c: Update readline-related comments.
	(input_handler, call_readline): Delete globals.
	(gdb_rl_callback_handler): Call the current UI's input_handler
	method.
	(change_line_handler): Adjust to set current UI's properties
	instead of globals.
	(current_ui_, current_ui): New globals.
	(get_command_line_buffer): Rewrite to refer to the current UI.
	(stdin_event_handler): Adjust to call the call_readline method of
	the current UI.
	(gdb_readline_no_editing_callback): Adjust to call the current UI's
	input_handler method.
	(gdb_setup_readline): Adjust to set current UI's properties
	instead of globals.
	* event-top.h (call_readline, input_handler): Delete declarations.
	* mi/mi-interp.c (mi_interpreter_resume): Adjust to set current
	UI's properties instead of globals.
	* top.c (gdb_readline_wrapper_cleanup): Adjust to set current UI's
	properties instead of globals.
	(gdb_readline_wrapper): Adjust to call and set current UI's
	methods instead of globals.
	* top.h: Include buffer.h and event-loop.h.
	(struct ui): New struct.
	(current_ui): New declaration.

1 files changed, 32 insertions, 1 deletions

diff --git a/gdb/top.h b/gdb/top.h
index a498f39..fc4e90a 100644
--- a/gdb/top.h
+++ b/gdb/top.h
@@ -20,7 +20,38 @@
 #ifndef TOP_H
 #define TOP_H
 
-struct buffer;
+#include "buffer.h"
+#include "event-loop.h"
+
+/* All about a user interface instance.  Each user interface has its
+   own I/O files/streams, readline state, its own top level
+   interpreter (for the main UI, this is the interpreter specified
+   with -i on the command line) and secondary interpreters (for
+   interpreter-exec ...), etc.  There's always one UI associated with
+   stdin/stdout/stderr, but the user can create secondary UIs, for
+   example, to create a separate MI channel on its own stdio
+   streams.  */
+
+struct ui
+{
+  /* The UI's command line buffer.  This is to used to accumulate
+     input until we have a whole command line.  */
+  struct buffer line_buffer;
+
+  /* The callback used by the event loop whenever an event is detected
+     on the UI's input file descriptor.  This function incrementally
+     builds a buffer where it accumulates the line read up to the
+     point of invocation.  In the special case in which the character
+     read is newline, the function invokes the INPUT_HANDLER callback
+     (see below).  */
+  void (*call_readline) (gdb_client_data);
+
+  /* The function to invoke when a complete line of input is ready for
+     processing.  */
+  void (*input_handler) (char *);
+};
+
+extern struct ui *current_ui;
 
 /* From top.c.  */
 extern char *saved_command_line;