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Info for developers

Some useful hints to make development of the project easier.

Adding new AppState field

Field such as baseKey, basePitch, octave, etc.

Last update of this instruction was in 29.04.2018.

When you add new app state field you'd probably need to handle it in different modules, such MIDIPlayer or GUI. Here's a list of places you probably would handle your new field:

  1. EventHandler module:
    1. Extend AppState data type with your new field;
    2. You may need to add a constructor of EventToHandle to change a value of your new field;
    3. Add default value of your new field to Default AppState instance;
    4. Add transform for new value of your new field to runEventHandler;
    5. If your field could shift current pitch:
      1. Check if it's changed in updateStateMiddleware to update pitch mapping;
      2. Add shift logic to getPitchMapping.
  2. Main module:
    1. Add handler to evListener (usually it updates a value in GUI), don't forget to update key mapping by sending SetPitchMapping event to the GUI (if your new field could affect key mapping);
    2. If GUI supposed to have representation of your new field:
      1. Add initial value to guiInitValues;
      2. Add GUI user interaction handler to guiIface that will trigger change to EventHandler.
  3. GUI module (if your new field has GUI representation):
    1. Add field of handler to GUIContext data type which would handle of updating your value from GUI to somewhere else (when value changed from GUI this handler will be called) (you may not need this if a value can't be changed from the GUI);
    2. Call that handler from some GUI element change handler (you may not need this if a value can't be changed from the GUI);
    3. Add GUI representation of your field to GUIState data type;
    4. Use that GUI state field somewhere to show it to the user;
    5. Extend GUIStateUpdate data type with setter of new value for your field to update a value in GUI when it changes from somewhere else;
    6. Go to place starts with takeMVar stateUpdateBus where these GUI state updates are handled and add proper handler for update of your new field value.