[hoc-users] Information on how to build a custom NSView subclass

[Joe J. <dar...@gm...>]

First, understand that I am a complete newbie to Haskell and HOC so
please forgive me if this seems rather basic. I have checked the users
archive and was unable to find an answer to this.

I am trying to create a custom NSView subclass that, specifically one
that overrides drawRect. What I am having a problem with is
understanding how to override this function and how to actually get
some custom drawing done. Actually, I;m not even sure if my class is
being instantiated. I slapped a view into the ExpressionParser window,
gave it a custom class with the same name as my class (which would
normally be all I would need to do in Cocoa).

Here is what I have for my view so far:

{-# OPTIONS -fglasgow-exts -fth #-}

module EPView where

import Cocoa

$(declareClass "EPView" "NSView")

$(exportClass "EPView" "ev_"
  [
  {-
  Outlet "expressionEntry" [t| NSTextField () |]
  , Outlet "evaluation"      [t| NSTextField () |]
  ,-}
   InstanceMethod 'drawRect
  ]
 )

obj #. var = obj # getIVar var

ev_drawRect rect self = do
        putStrLn "Hello World"


The putStrLn is there just to get something into that method. I think
it is doing something (as I see traces of Hell World in the console
log, though not consistent). What I am trying to do is to get
something to draw (right now nothing more complex then filling in the
rect that is passed in with a blackColor from NSColor.

Can anyone provide some pointers (or some code) for this problem?

Thanx,
joe