curses line-of-input prompting

Redo the fake ESC handling for curses' wgetnstr() so that it
applies to all popup prompts rather than just to "Who are you?",
in case the player sets the 'popup_dialog' option.

win/curses/cursdial.c

@@ -131,7 +131,8 @@ curses_line_input_dialog(const char *prompt, char *answer, int buffer)
     int map_height, map_width, maxwidth, remaining_buf, winx, winy, count;
     WINDOW *askwin, *bwin;
     char *tmpstr;
-    int prompt_width, prompt_height = 1, height = prompt_height;
+    int prompt_width, prompt_height = 1, height = prompt_height,
+        answerx = 0, answery = 0, trylim;
     char input[BUFSZ];
 
     /* if messages were being suppressed for the remainder of the turn,
@@ -185,11 +186,28 @@ curses_line_input_dialog(const char *prompt, char *answer, int buffer)
                 wmove(askwin, count + 1, 0);
         }
         free(tmpstr);
+        /* remember where user's typed response will start, in case we
+           need to re-prompt */
+        getyx(askwin, answery, answerx);
     }
 
     echo();
     curs_set(1);
-    wgetnstr(askwin, input, buffer - 1);
+    trylim = 10;
+    do {
+        /* move and clear are only needed for 2nd and subsequent passes */
+        wmove(askwin, answery, answerx);
+        wclrtoeol(askwin);
+
+        wgetnstr(askwin, input, buffer - 1);
+        /* ESC after some input kills that input and tries again;
+           ESC at the start cancels, leaving ESC in the result buffer.
+           [Note: wgetnstr() treats <escape> as an ordinary character
+           so user has to type <escape><return> for it to behave the
+           way we want it to.] */
+        if (input[0] != '\033' && index(input, '\033') != 0)
+             input[0] = '\0';
+    } while (--trylim > 0 && !input[0]);
     curs_set(0);
     Strcpy(answer, input);
     werase(bwin);