anagrams.tlv: slightly more responsive

Now we cancel screen-painting if any key is pressed.

However it looks like just computing the list of anagrams can take a
long time.

anagrams.tlv

@@ -228,6 +228,7 @@
 - __teliva_timestamp: original
   main:
     >function main()
+    >  Window:nodelay(true)
     >  while true do
     >    render(Window)
     >    update(Window)
@@ -236,7 +237,11 @@
 - __teliva_timestamp: original
   update:
     >function update(window)
-    >  local key = window:getch()
+    >  local key
+    >  while true do
+    >    key = window:getch()
+    >    if key then break end
+    >  end
     >  if key == curses.KEY_LEFT then
     >    if cursor > 1 then
     >      cursor = cursor-1
@@ -277,6 +282,11 @@
     >    for i, w in ipairs(results) do
     >      window:addstr(w)
     >      window:addstr(' ')
+    >      local tmp = window:getch()
+    >      if tmp then
+    >        window:ungetch(tmp)
+    >        break
+    >      end
     >    end
     >  end
     >

src/lcurses/window.c

@@ -1360,6 +1360,25 @@ Wgetch(lua_State *L)
 }
 
 
+/***
+Put back a character obtained from @{getch}
+@function ungetch
+@int ch
+@treturn OK or ERR
+@see mvwgetch(3x)
+@see getch
+*/
+static int
+Wungetch(lua_State *L)
+{
+	int ch = checkint(L, 2);
+	int result = ungetch(ch);
+	if (result == ERR)
+		return 0;
+	return pushintresult(result);
+}
+
+
 /***
 Call @{move} then @{getch}
 @function mvgetch
@@ -1893,6 +1912,7 @@ static const luaL_Reg curses_window_fns[] =
 	LCURSES_FUNC( Wtimeout		),
 	LCURSES_FUNC( Wtouch		),
 	LCURSES_FUNC( Wtouchline	),
+	LCURSES_FUNC( Wungetch		),
 	LCURSES_FUNC( Wvline		),
 	LCURSES_FUNC( Wwbkgd		),
 	LCURSES_FUNC( Wwbkgdset		),