Add a Features checkbox to disable bracketed paste mode.

I've had more than one conversation recently in which users have
mentioned finding this mode inconvenient. I don't know whether any of
them would want to turn it off completely, but it seems likely that
_somebody_ will, sooner or later. So here's an option to do that.

conf.h

@@ -903,6 +903,11 @@ CONF_OPTION(no_bidi,
     DEFAULT_BOOL(false),
     SAVE_KEYWORD("DisableBidi"),
 )
+CONF_OPTION(no_bracketed_paste,
+    VALUE_TYPE(BOOL),
+    DEFAULT_BOOL(false),
+    SAVE_KEYWORD("DisableBracketedPaste"),
+)
 
 /* Colour options */
 CONF_OPTION(ansi_colour,

config.c

@@ -2190,6 +2190,9 @@ void setup_config_box(struct controlbox *b, bool midsession,
     ctrl_checkbox(s, "Disable bidirectional text display",
                   'd', HELPCTX(features_bidi), conf_checkbox_handler,
                   I(CONF_no_bidi));
+    ctrl_checkbox(s, "Disable bracketed paste mode",
+                  'p', HELPCTX(features_bracketed_paste), conf_checkbox_handler,
+                  I(CONF_no_bracketed_paste));
 
     /*
      * The Window panel.

doc/config.but

@@ -984,6 +984,34 @@ right in all situations.
 You may also find you need to disable Arabic text shaping;
 see \k{config-features-shaping}.
 
+\S{config-features-bracketed paste} Disabling \i{bracketed paste} mode
+
+By default, when you paste text into the terminal window, it's sent to
+the server as terminal input, exactly as if you'd typed the same text
+into the terminal window using the keyboard (except that it's all sent
+at once, much faster than you could type it).
+
+However, a terminal application can change that, by asking the
+terminal to enable \q{bracketed paste mode}. In this mode, pasted data
+is marked in the input stream, by sending a special control sequence
+before the paste, and another one at the end.
+
+A terminal application can use this information to treat pasted data
+differently from keyboard input. For example, a terminal-based text
+editor can treat the input as literal data, even if some of its
+characters would normally trigger special editor functions. A shell
+can treat pasted input as less trusted, in case another application
+somehow sneaked a malicious shell command into your clipboard: modern
+versions of \cw{bash} will highlight pasted data on the command line,
+and not run it until you've confirmed it by pressing Return, even if
+the pasted data contained a newline character.
+
+In edge cases, it's possible that bracketed paste mode introduces
+bigger problems than the ones it solves. So you can use this checkbox
+to turn it off completely. If you do that, then PuTTY will always send
+your paste data exactly as if it had been typed at the keyboard,
+whether or not the server asked for bracketed paste mode.
+
 \H{config-window} The Window panel
 
 The Window configuration panel allows you to control aspects of the

doc/index.but

@@ -77,6 +77,8 @@ from other protocols
 \IM{copy and paste} cut and paste
 \IM{copy and paste} paste, copy and
 
+\IM{bracketed paste} paste, bracketed
+
 \IM{three-button mouse} three-button mouse
 \IM{three-button mouse} mouse, three-button
 

terminal/terminal.c

@@ -1639,6 +1639,7 @@ static void term_copy_stuff_from_conf(Terminal *term)
     term->bellovl_s = conf_get_int(term->conf, CONF_bellovl_s);
     term->bellovl_t = conf_get_int(term->conf, CONF_bellovl_t);
     term->no_bidi = conf_get_bool(term->conf, CONF_no_bidi);
+    term->no_bracketed_paste = conf_get_bool(term->conf, CONF_no_bracketed_paste);
     term->bksp_is_delete = conf_get_bool(term->conf, CONF_bksp_is_delete);
     term->blink_cur = conf_get_bool(term->conf, CONF_blink_cur);
     term->blinktext = conf_get_bool(term->conf, CONF_blinktext);
@@ -7130,7 +7131,7 @@ void term_do_paste(Terminal *term, const wchar_t *data, int len)
     term->paste_pos = term->paste_len = 0;
     term->paste_buffer = snewn(len + 12, wchar_t);
 
-    if (term->bracketed_paste)
+    if (term->bracketed_paste && !term->no_bracketed_paste)
         term_bracketed_paste_start(term);
 
     p = data;

terminal/terminal.h

@@ -157,6 +157,7 @@ struct terminal_tag {
     int raw_mouse_reported_y;
 
     bool bracketed_paste, bracketed_paste_active;
+    bool no_bracketed_paste;           /* disabled in configuration */
 
     int cset_attr[2];
 

windows/help.h

@@ -45,6 +45,7 @@ typedef const char *HelpCtx;
 #define WINHELP_CTX_features_clearscroll "config-features-clearscroll"
 #define WINHELP_CTX_features_arabicshaping "config-features-shaping"
 #define WINHELP_CTX_features_bidi "config-features-bidi"
+#define WINHELP_CTX_features_bracketed_paste "config-features-bracketed-paste"
 #define WINHELP_CTX_terminal_autowrap "config-autowrap"
 #define WINHELP_CTX_terminal_decom "config-decom"
 #define WINHELP_CTX_terminal_lfhascr "config-crlf"