kconfig/lxdialog: let <ESC><ESC> behave as expected

<ESC><ESC> is used to step one back in the dialogs.
When lxdialog became built-in pressing <ESC> once would cause one step back
and pressing <ESC><ESC> would cause two steps back.
This patch - based on concept from Roman Zippel <zippel@linux-m68k.org> -
makes one <ESC> a noop and pressing <ESC><ESC> will cause one step backward.

In addition the final yes/no dialog now has the option to go back to the
the kernel configuration. So if you get too far out you can now go back
to configuring the kernel without saving and starting all over again.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

7 files changed, 62 insertions, 19 deletions

diff --git a/scripts/kconfig/lxdialog/checklist.c b/scripts/kconfig/lxdialog/checklist.c
index 282511020bcb..39becb72444a 100644
--- a/scripts/kconfig/lxdialog/checklist.c
+++ b/scripts/kconfig/lxdialog/checklist.c
@@ -192,7 +192,7 @@ int dialog_checklist(const char *title, const char *prompt, int height,
         wnoutrefresh(list);
         doupdate();
 
-        while (key != ESC) {
+        while (key != KEY_ESC) {
                 key = wgetch(dialog);
 
                 for (i = 0; i < max_choice; i++) {
@@ -298,8 +298,10 @@ int dialog_checklist(const char *title, const char *prompt, int height,
                         break;
                 case 'X':
                 case 'x':
-                        key = ESC;
-                case ESC:
+                        key = KEY_ESC;
+                        break;
+                case KEY_ESC:
+                        key = on_key_esc(dialog);
                         break;
                 }
 
@@ -308,5 +310,5 @@ int dialog_checklist(const char *title, const char *prompt, int height,
         }
         delwin(list);
         delwin(dialog);
-        return 255;             /* ESC pressed */
+        return key;             /* ESC pressed */
 }
diff --git a/scripts/kconfig/lxdialog/dialog.h b/scripts/kconfig/lxdialog/dialog.h
index 065ded0a449f..a7cfdecc2409 100644
--- a/scripts/kconfig/lxdialog/dialog.h
+++ b/scripts/kconfig/lxdialog/dialog.h
@@ -48,7 +48,7 @@
 
 #define TR(params) _tracef params
 
-#define ESC 27
+#define KEY_ESC 27
 #define TAB 9
 #define MAX_LEN 2048
 #define BUF_SIZE (10*1024)
@@ -179,6 +179,8 @@ int item_is_tag(char tag);
         for (item_cur = item_head ? item_head: item_cur; \
              item_cur && (item_cur != &item_nil); item_cur = item_cur->next)
 
+/* generic key handlers */
+int on_key_esc(WINDOW *win);
 
 void init_dialog(const char *backtitle);
 void reset_dialog(void);
diff --git a/scripts/kconfig/lxdialog/inputbox.c b/scripts/kconfig/lxdialog/inputbox.c
index 9c53098d6b74..edb7975dbaa2 100644
--- a/scripts/kconfig/lxdialog/inputbox.c
+++ b/scripts/kconfig/lxdialog/inputbox.c
@@ -106,7 +106,7 @@ int dialog_inputbox(const char *title, const char *prompt, int height, int width
 
         wrefresh(dialog);
 
-        while (key != ESC) {
+        while (key != KEY_ESC) {
                 key = wgetch(dialog);
 
                 if (button == -1) {     /* Input box selected */
@@ -215,12 +215,14 @@ int dialog_inputbox(const char *title, const char *prompt, int height, int width
                         return (button == -1 ? 0 : button);
                 case 'X':
                 case 'x':
-                        key = ESC;
-                case ESC:
+                        key = KEY_ESC;
+                        break;
+                case KEY_ESC:
+                        key = on_key_esc(dialog);
                         break;
                 }
         }
 
         delwin(dialog);
-        return 255;             /* ESC pressed */
+        return KEY_ESC;         /* ESC pressed */
 }
diff --git a/scripts/kconfig/lxdialog/menubox.c b/scripts/kconfig/lxdialog/menubox.c
index f39ae29f4fcc..d3305bad15c7 100644
--- a/scripts/kconfig/lxdialog/menubox.c
+++ b/scripts/kconfig/lxdialog/menubox.c
@@ -263,7 +263,7 @@ int dialog_menu(const char *title, const char *prompt, int height, int width,
         wmove(menu, choice, item_x + 1);
         wrefresh(menu);
 
-        while (key != ESC) {
+        while (key != KEY_ESC) {
                 key = wgetch(menu);
 
                 if (key < 256 && isalpha(key))
@@ -402,12 +402,14 @@ int dialog_menu(const char *title, const char *prompt, int height, int width,
                         return button;
                 case 'e':
                 case 'x':
-                        key = ESC;
-                case ESC:
+                        key = KEY_ESC;
+                        break;
+                case KEY_ESC:
+                        key = on_key_esc(menu);
                         break;
                 }
         }
         delwin(menu);
         delwin(dialog);
-        return 255;             /* ESC pressed */
+        return key;             /* ESC pressed */
 }
diff --git a/scripts/kconfig/lxdialog/textbox.c b/scripts/kconfig/lxdialog/textbox.c
index 86b0770b0387..a99e1f497d67 100644
--- a/scripts/kconfig/lxdialog/textbox.c
+++ b/scripts/kconfig/lxdialog/textbox.c
@@ -92,7 +92,7 @@ int dialog_textbox(const char *title, const char *tbuf, int height, int width)
         wmove(dialog, cur_y, cur_x);    /* Restore cursor position */
         wrefresh(dialog);
 
-        while ((key != ESC) && (key != '\n')) {
+        while ((key != KEY_ESC) && (key != '\n')) {
                 key = wgetch(dialog);
                 switch (key) {
                 case 'E':       /* Exit */
@@ -228,13 +228,14 @@ int dialog_textbox(const char *title, const char *tbuf, int height, int width)
                         wmove(dialog, cur_y, cur_x);
                         wrefresh(dialog);
                         break;
-                case ESC:
+                case KEY_ESC:
+                        key = on_key_esc(dialog);
                         break;
                 }
         }
         delwin(text);
         delwin(dialog);
-        return 255;             /* ESC pressed */
+        return key;             /* ESC pressed */
 }
 
 /*
diff --git a/scripts/kconfig/lxdialog/util.c b/scripts/kconfig/lxdialog/util.c
index 0b3118df50df..cb21dc4dd9fc 100644
--- a/scripts/kconfig/lxdialog/util.c
+++ b/scripts/kconfig/lxdialog/util.c
@@ -477,6 +477,39 @@ int first_alpha(const char *string, const char *exempt)
         return 0;
 }
 
+/*
+ * ncurses uses ESC to detect escaped char sequences. This resutl in
+ * a small timeout before ESC is actually delivered to the application.
+ * lxdialog suggest <ESC> <ESC> which is correctly translated to two
+ * times esc. But then we need to ignore the second esc to avoid stepping
+ * out one menu too much. Filter away all escaped key sequences since
+ * keypad(FALSE) turn off ncurses support for escape sequences - and thats
+ * needed to make notimeout() do as expected.
+ */
+int on_key_esc(WINDOW *win)
+{
+        int key;
+        int key2;
+        int key3;
+
+        nodelay(win, TRUE);
+        keypad(win, FALSE);
+        key = wgetch(win);
+        key2 = wgetch(win);
+        do {
+                key3 = wgetch(win);
+        } while (key3 != ERR);
+        nodelay(win, FALSE);
+        keypad(win, TRUE);
+        if (key == KEY_ESC && key2 == ERR)
+                return KEY_ESC;
+        else if (key != ERR && key != KEY_ESC && key2 == ERR)
+                ungetch(key);
+
+        return -1;
+}
+
+
 struct dialog_list *item_cur;
 struct dialog_list item_nil;
 struct dialog_list *item_head;
diff --git a/scripts/kconfig/lxdialog/yesno.c b/scripts/kconfig/lxdialog/yesno.c
index 9fc24492c52f..8364f9dd01c3 100644
--- a/scripts/kconfig/lxdialog/yesno.c
+++ b/scripts/kconfig/lxdialog/yesno.c
@@ -69,7 +69,7 @@ int dialog_yesno(const char *title, const char *prompt, int height, int width)
 
         print_buttons(dialog, height, width, 0);
 
-        while (key != ESC) {
+        while (key != KEY_ESC) {
                 key = wgetch(dialog);
                 switch (key) {
                 case 'Y':
@@ -93,11 +93,12 @@ int dialog_yesno(const char *title, const char *prompt, int height, int width)
                 case '\n':
                         delwin(dialog);
                         return button;
-                case ESC:
+                case KEY_ESC:
+                        key = on_key_esc(dialog);
                         break;
                 }
         }
 
         delwin(dialog);
-        return 255;             /* ESC pressed */
+        return key;             /* ESC pressed */
 }