vi(1)-style half page scroll in copy and scroll modes. Move the vi full page

scroll key to C-b instead of C-u and use C-u/C-d for half page scrolling with
vi keys. In emacs mode, half page scrolling is bound to M-Up and M-Down.

Suggested by merdely (about a year ago :-)).

mode-key.c

@@ -149,10 +149,12 @@ const struct mode_key_entry mode_key_vi_copy[] = {
 	{ ' ',			0, MODEKEYCOPY_STARTSELECTION },
 	{ '$',			0, MODEKEYCOPY_ENDOFLINE },
 	{ '0',			0, MODEKEYCOPY_STARTOFLINE },
+	{ '\002' /* C-b */,	0, MODEKEYCOPY_PREVIOUSPAGE },
 	{ '\003' /* C-c */,	0, MODEKEYCOPY_CANCEL },
+	{ '\004' /* C-d */,	0, MODEKEYCOPY_HALFPAGEDOWN },
 	{ '\006' /* C-f */,	0, MODEKEYCOPY_NEXTPAGE },
 	{ '\010' /* C-h */,	0, MODEKEYCOPY_LEFT },
-	{ '\025' /* C-u */,	0, MODEKEYCOPY_PREVIOUSPAGE },
+	{ '\025' /* C-u */,	0, MODEKEYCOPY_HALFPAGEUP },
 	{ '\033' /* Escape */,	0, MODEKEYCOPY_CLEARSELECTION },
 	{ '\r',			0, MODEKEYCOPY_COPYSELECTION },
 	{ '^',			0, MODEKEYCOPY_BACKTOINDENTATION },
@@ -237,11 +239,13 @@ const struct mode_key_entry mode_key_emacs_copy[] = {
 	{ 'q',			0, MODEKEYCOPY_CANCEL },
 	{ 'v' | KEYC_ESCAPE,	0, MODEKEYCOPY_PREVIOUSPAGE },
 	{ 'w' | KEYC_ESCAPE,	0, MODEKEYCOPY_COPYSELECTION },
+	{ KEYC_DOWN | KEYC_ESCAPE, 0, MODEKEYCOPY_HALFPAGEDOWN },
 	{ KEYC_DOWN,		0, MODEKEYCOPY_DOWN },
 	{ KEYC_LEFT,		0, MODEKEYCOPY_LEFT },
 	{ KEYC_NPAGE,		0, MODEKEYCOPY_NEXTPAGE },
 	{ KEYC_PPAGE,		0, MODEKEYCOPY_PREVIOUSPAGE },
 	{ KEYC_RIGHT,		0, MODEKEYCOPY_RIGHT },
+	{ KEYC_UP | KEYC_ESCAPE, 0, MODEKEYCOPY_HALFPAGEUP },
 	{ KEYC_UP,		0, MODEKEYCOPY_UP },
 
 	{ 0,			-1, 0 }	

tmux.h

@@ -388,12 +388,14 @@ enum mode_key_cmd {
 	MODEKEYCHOICE_UP,
 
 	/* Copy keys. */
-	MODEKEYCOPY_CANCEL,
 	MODEKEYCOPY_BACKTOINDENTATION,
+	MODEKEYCOPY_CANCEL,
 	MODEKEYCOPY_CLEARSELECTION,
 	MODEKEYCOPY_COPYSELECTION,
 	MODEKEYCOPY_DOWN,
 	MODEKEYCOPY_ENDOFLINE,
+	MODEKEYCOPY_HALFPAGEDOWN,
+	MODEKEYCOPY_HALFPAGEUP,
 	MODEKEYCOPY_LEFT,
 	MODEKEYCOPY_NEXTPAGE,
 	MODEKEYCOPY_NEXTWORD,

window-copy.c

@@ -203,6 +203,24 @@ window_copy_key(struct window_pane *wp, struct client *c, int key)
 		window_copy_update_selection(wp);
 		window_copy_redraw_screen(wp);
 		break;
+	case MODEKEYCOPY_HALFPAGEUP:
+		n = screen_size_y(s) / 2;
+		if (data->oy + n > screen_hsize(&wp->base))
+			data->oy = screen_hsize(&wp->base);
+		else
+			data->oy += n;
+		window_copy_update_selection(wp);
+		window_copy_redraw_screen(wp);
+		break;
+	case MODEKEYCOPY_HALFPAGEDOWN:
+		n = screen_size_y(s) / 2;
+		if (data->oy < n)
+			data->oy = 0;
+		else
+			data->oy -= n;
+		window_copy_update_selection(wp);
+		window_copy_redraw_screen(wp);
+		break;
 	case MODEKEYCOPY_STARTSELECTION:
  		window_copy_start_selection(wp);
 		window_copy_redraw_screen(wp);

window-scroll.c

@@ -165,6 +165,22 @@ window_scroll_key(struct window_pane *wp, unused struct client *c, int key)
 			data->oy -= n;
 		window_scroll_redraw_screen(wp);
 		break;
+	case MODEKEYCOPY_HALFPAGEUP:
+		n = screen_size_y(s) / 2;
+		if (data->oy + n > screen_hsize(&wp->base))
+			data->oy = screen_hsize(&wp->base);
+		else
+			data->oy += n;
+		window_scroll_redraw_screen(wp);
+		break;
+	case MODEKEYCOPY_HALFPAGEDOWN:
+		n = screen_size_y(s) / 2;
+		if (data->oy < n)
+			data->oy = 0;
+		else
+			data->oy -= n;
+		window_scroll_redraw_screen(wp);
+		break;
 	default:
 		break;
 	}