Separate sketch window class

[Kevinpgalligan]

An attempt to fix the first render being lost due to window resizing (see: #69).

This is achieved by creating a separate sketch-window class so that sketch doesn't have to inherit from gl-window. That way, the slots of sketch can be initialized BEFORE the window gets created, and the window can be assigned the correct dimensions from the start, avoiding a resize.

Implementation notes:

• Since there may be a circular dependency between the sketch slots and the SDL2 window (specifically: trying to create textures during slot initialization would break because the OpenGL context of the window is not available yet), we have to delay their initialization. My approach is to create a skeleton image object, save a lambda that will do the OpenGL parts of image creation and update the imageobject, and then call all the lambdas after the window has been created.
• For backward compatibility with sketches that handle input via the kit.sdl2 methods, we have to forward those method calls to the sketch object.
• For some reason, the call to (gl:clear-color 0.0 1.0 0.0 1.0) in initialize-gl started taking effect after the refactoring, and the background colour of sketches with (copy-pixels t) suddenly became green if they didn't call background anywhere (they had a black background before - I'm not sure why!). So I just changed it to (gl:clear-color 0.0 0.0 0.0 1.0) for backward compatibility.

Various parts of the code, as well as debugging help, were contributed by @Gleefre :)

[Gleefre]

Might be more readable & efficient to use a macro like this:

(defmacro maybe-delayed (&body body &aux (thunk (gensym "thunk")))
  `(flet ((,thunk ()
            ,@body))
     (if (delay-init-p)
         (add-delayed-init-fun! (function ,thunk))
         (,thunk))))

And use it like this:

(defun init-image-texture! (...)
  (maybe-delayed
    (let ((texture (car (gl:gen-textures 1)))
          ...)
      ...)))

[Kevinpgalligan]

I think I'd prefer to leave it as-is. My rule of thumb is to use a macro only when necessary. The code could definitely be made more readable, though...

[Gleefre]

I'd suggest then to refactor to what would be a macroexpansion of maybe-delayed -- this way the function init-image-texture! will be called only once, also removing an extra call to delay-init-p.

So something like this:

(defun init-image-texture! (...)
  (flet ((init ()
           ...))
    (if (delay-init-p)
        (add-delayed-init-fun! #'init)
        (init))))

[vydd]

I agree with @Gleefre here, and the remark agrees with the general codestyle in the repo. No need to fix it immediately though.

[Gleefre]

I'd suggest using alexandria:when-let here to avoid calling sketch-%window twice.

[Kevinpgalligan]

Hmm, tried this, but we still end up with alexandria:when-let on top of a let, so I don't think it makes much of a difference.

[Gleefre]

FWIW it could be moved into a forward method:

(defmethod kit.sdl2:sdl-window ((instance sketch))
  (alexandria:when-let (window (sketch-%window instance)
    (kit.sdl2:sdl-window window))

And then also used here:

(defmethod ...
  (alexandria:when-let (win (kit.sdl2:sdl-window instance))
    ,@body))

[Gleefre]

Another possibility would be to use alexandria:when-let* and move the second let there -- fwiw the sdl-window slot could be nil as well.

[Gleefre]

(But I don't insist on any of these changes of course; so feel free to resolve the comment thread :)

[Gleefre]

Why not to simply create a fresh vector?
Like this:

(setf fs (make-array 0 :adjustable t :fill-pointer t))

[Kevinpgalligan]

In my experience, SBCL won't necessarily garbage collect the elements of a complex data structure if they're not manually set to nil. (Happened to me with a massive tree of cons cells, but seems like good practice anyway).

[Gleefre]

I think that they will be collected alongside the vector though.