[PATCH v2] Make the TUI command window support the mouse

[Pedro Alves <pedro@palves.net>]

On 2021-06-12 7:08 p.m., Pedro Alves wrote:
> On 2021-06-12 1:32 p.m., Hannes Domani wrote:

>> On the other hand, if keypad was enabled, couldn't we just forward readline
>> the escape sequences for the arrow keys instead?
> 
> Yeah, to be honest I think that is likely a better approach and worth it of a
> try -- my only concern is whether the escape sequences are standard enough
> across terminals?  Maybe it's all covered by ANSI and it's all we need to care
> about?  I thought of the other approach because that let's us not care about
> specific sequences, other than the mouse sequence, which seemed pretty much
> standard from looking around.  Also, it was run to write.  :-)
> 

Alright, I gave that approach a go.  Below's a patch implementing that.  It
works quite nicely here.  I tried it on konsole, xterm and rxvt.  Among those,
rxvt uses different escape sequences for ctrl-up/ctrl-down/ctrl-left/ctrl-right,
but it doesn't really matter -- I found that readline binds actions to
different variants of escape sequences, so if we pick sequences readline always binds,
it should always work.  See readline.c:bind_arrow_keys_internal.
Despite that, for the standard ncurses keys below KEY_MAX, it's easier
to use the corresponding lowercase key_foo variable, which I believe is
filled in from termcap so should also always work, as readline also
binds the key sequences termcap returns.

Overall, I'm pleased with this approach.  See commit log for more, particularly
the extra improvement we get.

From: Pedro Alves <pedro@palves.net>
Date: 2021-06-05 19:11:09 +0100

Make the TUI command window support the mouse

Currently, when the focus is on the command window, we disable the
keypad.  This means that when the command window has the focus, keys
such as up/down/home/end etc. are not processed by ncurses, and their
escape sequences go straight to readline.

A side effect of disabling keypad mode is that wgetch no longer
processes mouse escape sequences, with the end result being the mouse
doesn't work, and worse, the raw mouse escape sequences are printed on
the terminal.

This commit makes the TUI command window support the mouse as well, by
always enabling the keypad, and then to avoid losing support for
up/down browsing the command history, home/end/left/right moving the
cursor position, etc., we forward those keys as raw escape sequences
to readline.

Note that the patch makes it so that CTLC-L is already passed to
readline even if the command window does not have the focus.  It was
simpler to implement that way, and it just seems correct to me.  I
don't know of a reason we shouldn't do that.

The patch improves the TUI behavior in a related way.  Now we can pass
keys to readline irrespective of which window has focus.  First, we
try to dispatch the key to a window, via tui_displatch_ctrl_char.  If
the key is dispatched, then we don't pass it to readline.  E.g.,
pressing "up" when you have the source window in focus results in
scrolling the source window, and nothing else.  If however, you press
ctrl-del instead, that results in killing the next word in the command
window, no matter which window has focus.  Before, it would only work
if you had the command window in focus.  Similarly,
ctrl-left/ctrl-right to move between words, etc.

Similarly, the previous spot where we handled mouse events was
incorrect.  It was never reached if the window with focus can't
scroll, which is the case for the command window.  Mouse scrolling
affects the window under the mouse cursor, not the window in focus.
We now always try to dispatch mouse events.

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	* tui/tui-io.c (tui_dispatch_mouse_event): New, factored out from
	...
	(tui_dispatch_ctrl_char): ... this.  Move CTRL-L handling to
	tui_getc_1.
	(cur_seq, start_sequence): New.
	(tui_getc_1): Pass key escape sequences for ncurses control keys
	to readline.  Handle mouse and ctrl-l here.
	(tui_resize_all): Disable/reenable the keypad if the command
	window has the focus too.
	* tui/tui-win.c (tui_set_focus_command): Don't change keypad
	setting.
	* tui/tui.c (tui_rl_other_window): Don't change keypad setting.

Change-Id: Ie0a7d849943cfb47f4a6589e1c73341563740fa9

---

 gdb/tui/tui-io.c  |  195 ++++++++++++++++++++++++++++++++++++++++++-----------
 gdb/tui/tui-win.c |   12 +--
 gdb/tui/tui.c     |    5 -
 3 files changed, 160 insertions(+), 52 deletions(-)

diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
index 7df0e2f1bd3..4da6f2bab11 100644
--- a/gdb/tui/tui-io.c
+++ b/gdb/tui/tui-io.c
@@ -946,6 +946,38 @@ tui_initialize_io (void)
 #endif
 }
 
+/* Dispatch the correct tui function based upon the mouse event.  */
+
+static void
+tui_dispatch_mouse_event ()
+{
+  MEVENT mev;
+  if (getmouse (&mev) != OK)
+    return;
+
+  for (tui_win_info *wi : all_tui_windows ())
+    if (mev.x > wi->x && mev.x < wi->x + wi->width - 1
+	&& mev.y > wi->y && mev.y < wi->y + wi->height - 1)
+      {
+	if ((mev.bstate & BUTTON1_CLICKED) != 0
+	    || (mev.bstate & BUTTON2_CLICKED) != 0
+	    || (mev.bstate & BUTTON3_CLICKED) != 0)
+	  {
+	    int button = (mev.bstate & BUTTON1_CLICKED) != 0 ? 1
+	      :         ((mev.bstate & BUTTON2_CLICKED) != 0 ? 2
+			 : 3);
+	    wi->click (mev.x - wi->x - 1, mev.y - wi->y - 1, button);
+	  }
+#ifdef BUTTON5_PRESSED
+	else if ((mev.bstate & BUTTON4_PRESSED) != 0)
+	  wi->backward_scroll (3);
+	else if ((mev.bstate & BUTTON5_PRESSED) != 0)
+	  wi->forward_scroll (3);
+#endif
+	break;
+      }
+}
+
 /* Dispatch the correct tui function based upon the control
    character.  */
 static unsigned int
@@ -953,10 +985,6 @@ tui_dispatch_ctrl_char (unsigned int ch)
 {
   struct tui_win_info *win_info = tui_win_with_focus ();
 
-  /* Handle the CTRL-L refresh for each window.  */
-  if (ch == '\f')
-    tui_refresh_all_win ();
-
   /* If no window has the focus, or if the focus window can't scroll,
      just pass the character through.  */
   if (win_info == NULL || !win_info->can_scroll ())
@@ -984,39 +1012,6 @@ tui_dispatch_ctrl_char (unsigned int ch)
     case KEY_LEFT:
       win_info->right_scroll (1);
       break;
-#ifdef NCURSES_MOUSE_VERSION
-    case KEY_MOUSE:
-	{
-	  MEVENT mev;
-	  if (getmouse (&mev) != OK)
-	    break;
-
-	  for (tui_win_info *wi : all_tui_windows ())
-	    if (mev.x > wi->x && mev.x < wi->x + wi->width - 1
-		&& mev.y > wi->y && mev.y < wi->y + wi->height - 1)
-	      {
-		if ((mev.bstate & BUTTON1_CLICKED) != 0
-		    || (mev.bstate & BUTTON2_CLICKED) != 0
-		    || (mev.bstate & BUTTON3_CLICKED) != 0)
-		  {
-		    int button = (mev.bstate & BUTTON1_CLICKED) != 0 ? 1
-		      :         ((mev.bstate & BUTTON2_CLICKED) != 0 ? 2
-				 : 3);
-		    wi->click (mev.x - wi->x - 1, mev.y - wi->y - 1, button);
-		  }
-#ifdef BUTTON5_PRESSED
-		else if ((mev.bstate & BUTTON4_PRESSED) != 0)
-		  wi->backward_scroll (3);
-		else if ((mev.bstate & BUTTON5_PRESSED) != 0)
-		  wi->forward_scroll (3);
-#endif
-		break;
-	      }
-	}
-      break;
-#endif
-    case '\f':
-      break;
     default:
       /* We didn't recognize the character as a control character, so pass it
 	 through.  */
@@ -1067,6 +1062,24 @@ tui_inject_newline_into_command_window ()
     }
 }
 
+/* If we're passing an escape sequence to readline, this points to a
+   string holding the remaining characters of the sequence to pass.
+   We advance the pointer one character at a time until '\0' is
+   reached.  */
+static const char *cur_seq = nullptr;
+
+/* Set CUR_SEQ to point at the current sequence to pass to readline,
+   setup to call the input handler again so we complete the sequence
+   shortly, and return the first character to start the sequence.  */
+
+static int
+start_sequence (const char *seq)
+{
+  call_stdin_event_handler_again_p = 1;
+  cur_seq = seq + 1;
+  return seq[0];
+}
+
 /* Main worker for tui_getc.  Get a character from the command window.
    This is called from the readline package, but wrapped in a
    try/catch by tui_getc.  */
@@ -1084,11 +1097,115 @@ tui_getc_1 (FILE *fp)
   tui_readline_output (0, 0);
 #endif
 
-  ch = gdb_wgetch (w);
+  /* We enable keypad mode so that ncurses's wgetch processes mouse
+     escape sequences.  In keypad mode, wgetch also processes the
+     escape sequences for keys such as up/down etc. and returns KEY_UP
+     / KEY_DOWN etc.  When we have the focus on the command window
+     though, we want to pass the raw up/down etc. escape codes to
+     readline so readline understands them.  */
+  if (cur_seq != nullptr)
+    {
+      ch = *cur_seq++;
+
+      /* If we've reached the end of the string, we're done with the
+	 sequence.  Otherwise, setup to get back here again for
+	 another character.  */
+      if (*cur_seq == '\0')
+	cur_seq = nullptr;
+      else
+	call_stdin_event_handler_again_p = 1;
+      return ch;
+    }
+  else
+    ch = gdb_wgetch (w);
 
   /* Handle prev/next/up/down here.  */
   ch = tui_dispatch_ctrl_char (ch);
-  
+
+#ifdef NCURSES_MOUSE_VERSION
+  if (ch == KEY_MOUSE)
+    {
+      tui_dispatch_mouse_event ();
+      return 0;
+    }
+#endif
+
+  /* Translate ncurses keys back to escape sequences so that readline
+     can understand them.  We do this irrespective of what is the
+     focus window.  If e.g., we're focused on a non-command window,
+     then the up/down keys will already have been filtered by
+     tui_dispatch_ctrl_char.  Keys that haven't been intercepted will
+     be passed down to readline.  */
+  if (current_ui->command_editing)
+    {
+      /* For the standard keys, we can find them efficiently in the
+	 key_xxx macros, defined by ncurses.  We could also hardcode
+	 sequences readline understands, and/or use rl_get_termcap.
+	 See readline/readline.c:bind_arrow_keys_internal for
+	 hardcoded sequences.  */
+      switch (ch)
+	{
+	case KEY_NPAGE: /* page down */
+	  return start_sequence (key_npage);
+	case KEY_PPAGE: /* page up */
+	  return start_sequence (key_ppage);
+	case KEY_DOWN:
+	  return start_sequence (key_down);
+	case KEY_UP:
+	  return start_sequence (key_up);
+	case KEY_RIGHT:
+	  return start_sequence (key_right);
+	case KEY_LEFT:
+	  return start_sequence (key_left);
+	case KEY_HOME:
+	  return start_sequence (key_home);
+	case KEY_END:
+	  return start_sequence (key_end);
+	case KEY_DC: /* del */
+	  return start_sequence (key_dc);
+	case KEY_IC: /* ins */
+	  return start_sequence (key_ic);
+	}
+
+      /* Keycodes above KEY_MAX are not garanteed to be stable.
+	 Compare keyname instead.  */
+      if (ch >= KEY_MAX)
+	{
+	  auto name = gdb::string_view (keyname (ch));
+
+	  /* ctrl-arrow keys */
+	  if (name == "kLFT5") /* ctrl-left */
+	    return start_sequence ("\033[1;5D");
+	  else if (name == "kRIT5") /* ctrl-right */
+	    return start_sequence ("\033[1;5C");
+	  else if (name == "kUP5") /* ctrl-up */
+	    return start_sequence ("\033[1;5A");
+	  else if (name == "kDN5") /* ctrl-down */
+	    return start_sequence ("\033[1;5B");
+	  else if (name == "kHOM5") /* ctrl-home */
+	    return start_sequence ("\033[1;5H");
+	  else if (name == "kEND5") /* ctrl-end */
+	    return start_sequence ("\033[1;5F");
+	  else if (name == "kIC5") /* ctrl-ins */
+	    return start_sequence ("\033[2;5~");
+	  else if (name == "kDC5") /* ctrl-del */
+	    return start_sequence ("\033[3;5~");
+
+	  /* alt-arrow keys */
+	  else if (name == "kLFT3") /* alt-left */
+	    return start_sequence ("\033[1;3D");
+	  else if (name == "kRIT3") /* alt-right */
+	    return start_sequence ("\033[1;3C");
+	}
+    }
+
+  /* Handle the CTRL-L refresh for each window.  */
+  if (ch == '\f')
+    {
+      tui_refresh_all_win ();
+      return ch;
+    }
+
   if (ch == KEY_BACKSPACE)
     return '\b';
 
diff --git a/gdb/tui/tui-win.c b/gdb/tui/tui-win.c
index 4e75a66a00e..a51e7b9f6da 100644
--- a/gdb/tui/tui-win.c
+++ b/gdb/tui/tui-win.c
@@ -498,14 +498,11 @@ tui_resize_all (void)
   height_diff = screenheight - tui_term_height ();
   if (height_diff || width_diff)
     {
-      struct tui_win_info *win_with_focus = tui_win_with_focus ();
-
 #ifdef HAVE_RESIZE_TERM
       resize_term (screenheight, screenwidth);
 #endif      
       /* Turn keypad off while we resize.  */
-      if (win_with_focus != TUI_CMD_WIN)
-	keypad (TUI_CMD_WIN->handle.get (), FALSE);
+      keypad (TUI_CMD_WIN->handle.get (), FALSE);
       tui_update_gdb_sizes ();
       tui_set_term_height_to (screenheight);
       tui_set_term_width_to (screenwidth);
@@ -515,10 +512,8 @@ tui_resize_all (void)
       erase ();
       clearok (curscr, TRUE);
       tui_apply_current_layout ();
-      /* Turn keypad back on, unless focus is in the command
-	 window.  */
-      if (win_with_focus != TUI_CMD_WIN)
-	keypad (TUI_CMD_WIN->handle.get (), TRUE);
+      /* Turn keypad back on.  */
+      keypad (TUI_CMD_WIN->handle.get (), TRUE);
     }
 }
 
@@ -703,7 +698,6 @@ tui_set_focus_command (const char *arg, int from_tty)
     error (_("Window \"%s\" is not visible"), arg);
 
   tui_set_win_focus_to (win_info);
-  keypad (TUI_CMD_WIN->handle.get (), win_info != TUI_CMD_WIN);
   printf_filtered (_("Focus set to %s window.\n"),
 		   tui_win_with_focus ()->name ());
 }
diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c
index 529fc62c9ac..5f0c87c05e1 100644
--- a/gdb/tui/tui.c
+++ b/gdb/tui/tui.c
@@ -179,10 +179,7 @@ tui_rl_other_window (int count, int key)
 
   win_info = tui_next_win (tui_win_with_focus ());
   if (win_info)
-    {
-      tui_set_win_focus_to (win_info);
-      keypad (TUI_CMD_WIN->handle.get (), win_info != TUI_CMD_WIN);
-    }
+    tui_set_win_focus_to (win_info);
   return 0;
 }