CODEWITHSUNDEEP
lispsdlracket
SurvivalMachine
SurvivalMachine

Reputation: 8356

Initializing an SDL rectangle in Racket and racket-sdl

I'm learning Racket by writing an SDL application but I don't know how to initialize a rectangle structure. It's defined in racket-sdl as follows:

(define-cstruct _SDL_Rect
  ([x _int]
   [y _int]
   [w _int]
   [h _int]))

How do I create an instance of a rectangle? Specifically, I want to create a rectangle to pass into the following function as the last parameter:

(SDL_BlitSurface hello-world-surface #f screen-surface #f)

Upvotes: 2

Views: 751

Answers (1)

vukung
vukung

Reputation: 1884

First of all, if you are just starting out with Racket, I would recommend to use some of the packaged libraries for drawing, such as the GUI library's canvas or the OpenGL library.

The racket-sdl project, with only 3 commits (the last one being 2 years old), seems to me as no more than a feasibility test.

Still, your question is valid, so let's give you an answer. (define-cstruct ...) defines a C struct essentially as a pointer, so you have no obvious means to change its internals. You can create a small wrapper library in C with a function make_SDL_Rect, and use that, but it isn't worth the hassle. It would be better to define the SDL_Rect type using make-cstruct-type, which allows for the conversion of parameters.

See more info at the FFI manual.

Upvotes: 4

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