bindings: allow toggling the help lines at several prompts and in browser

Now the help lines can be toggled not only while editing, but also at
the Read (^R), Write (^O), Execute (^T), Search (^W), Replace (M-R),
Goto (^/), and Yesno prompts, and also in the file browser and when
searching for a file name.  The help lines cannot be toggled in the
help viewer, nor when searching in a help text, nor in the linter,
as these three things force the help lines to be on.

Furthermore, the 'nohelp' function can be rebound in all relevant
menus (default binding: M-X).

This fulfills https://savannah.gnu.org/bugs/?58471.

src/browser.c

@@ -168,6 +168,12 @@ char *do_browser(char *path)
 #endif
 #else
 			say_there_is_no_help();
+#endif
+#ifndef NANO_TINY
+		} else if (func == do_toggle_void) {
+			TOGGLE(NO_HELP);
+			window_init();
+			kbinput = KEY_WINCH;
 #endif
 		} else if (func == do_search_forward) {
 			do_filesearch(FORWARD);

src/global.c

@@ -1345,7 +1345,7 @@ void shortcut_init(void)
 
 #ifndef NANO_TINY
 	/* Group of "Appearance" toggles. */
-	add_to_sclist(MMAIN, "M-X", 0, do_toggle_void, NO_HELP);
+	add_to_sclist((MMOST|MBROWSER|MYESNO) & ~MFINDINHELP, "M-X", 0, do_toggle_void, NO_HELP);
 	add_to_sclist(MMAIN, "M-C", 0, do_toggle_void, CONSTANT_SHOW);
 	add_to_sclist(MMAIN, "M-S", 0, do_toggle_void, SOFTWRAP);
 	add_to_sclist(MMAIN, "M-$", 0, do_toggle_void, SOFTWRAP);

src/prompt.c

@@ -515,6 +515,14 @@ functionptrtype acquire_an_answer(int *actual, bool allow_tabs,
 #ifndef NANO_TINY
 		else if (func == do_nothing)
 			finished = FALSE;
+		else if (func == do_toggle_void) {
+			TOGGLE(NO_HELP);
+			window_init();
+			focusing = FALSE;
+			refresh_func();
+			bottombars(currmenu);
+			finished = FALSE;
+		}
 #endif
 
 		/* If we have a shortcut with an associated function, break out if
@@ -741,6 +749,15 @@ int do_yesno_prompt(bool all, const char *msg)
 #endif /* ENABLE_MOUSE */
 		else if (func_from_key(&kbinput) == full_refresh)
 			full_refresh();
+#ifndef NANO_TINY
+		else if (func_from_key(&kbinput) == do_toggle_void) {
+			TOGGLE(NO_HELP);
+			window_init();
+			titlebar(NULL);
+			focusing = FALSE;
+			edit_refresh();
+		}
+#endif
 		else
 			beep();
 

src/rcfile.c

@@ -816,10 +816,12 @@ void parse_binding(char *ptr, bool dobind)
 		goto free_things;
 
 	/* Limit the given menu to those where the function exists;
-	 * first handle four special cases, then the general case. */
+	 * first handle five special cases, then the general case. */
 	if (is_universal(newsc->func))
 		menu &= MMOST|MBROWSER;
 #ifndef NANO_TINY
+	else if (newsc->func == do_toggle_void && newsc->toggle == NO_HELP)
+		menu &= (MMOST|MBROWSER|MYESNO) & ~MFINDINHELP;
 	else if (newsc->func == do_toggle_void)
 		menu &= MMAIN;
 #endif