lib/gamnit/keys.nit

   1 # This file is part of NIT (http://www.nitlanguage.org).
   2 #
   3 # Licensed under the Apache License, Version 2.0 (the "License");
   4 # you may not use this file except in compliance with the License.
   5 # You may obtain a copy of the License at
   6 #
   7 #        http://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 # Unless required by applicable law or agreed to in writing, software
  10 # distributed under the License is distributed on an "AS IS" BASIS,
  11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 # See the License for the specific language governing permissions and
  13 # limitations under the License.
  14
  15 # Simple service keeping track of which keys are currently pressed
  16 #
  17 # This service revolves around `app.pressed_keys`, a `Set` of the names of currently pressed keys.
  18 # As a `Set`, `app.pressed_keys` can be iterated and queried with `has`.
  19 #
  20 # Limitations: The keys names are platform dependent.
  21 #
  22 # ~~~nitish
  23 # redef class App
  24 #     redef fun accept_event(event)
  25 #     do
  26 #         # First, pass the event to `super`, `pressed_keys` must see all
  27 #         # events but it doesn't intercept any of them.
  28 #         if super then return true
  29 #         return false
  30 #     end
  31 #
  32 #     redef fun update(dt)
  33 #     do
  34 #         for key in pressed_keys do
  35 #             if k == "left" or k == "a" then
  36 #                 # Act on key pressed down
  37 #                 print "left or a is pressed down"
  38 #             end
  39 #         end
  40 #     end
  41 # end
  42 # ~~~
  43 module keys
  44
  45 import mnit::input
  46 import gamnit
  47
  48 redef class App
  49         # Currently pressed keys
  50         var pressed_keys = new Set[String] is lazy
  51
  52         # Register `event` to update `app.pressed_keys`
  53         private fun register_key_event(event: KeyEvent)
  54         do
  55                 var key = event.name
  56                 if event.is_down then
  57                         app.pressed_keys.add key
  58                 else if app.pressed_keys.has(key) then
  59                         app.pressed_keys.remove key
  60                 end
  61         end
  62
  63         redef fun accept_event(event)
  64         do
  65                 if event isa KeyEvent then register_key_event event
  66
  67                 return super
  68         end
  69 end