Customize the root of the project in the examples

[gpetiot]

I don't find it convenient to move into the directory of the examples to get them to work, as the paths to the resources are relative to that directory.

So, I propose to add an optional ROOT environment variable to each example, such as:

+let root = Bos.OS.Env.var "ROOT"
+
 let setup () =
   let open Raylib in
   init_window width height "raylib [textures] example - bunnymark";
-  let tex_bunny = load_texture "resources/wabbit_alpha.png" in
+  let tex_bunny =
+    let path =
+      match root with
+      | Some root -> Fmt.str "%s/resources/wabbit_alpha.png" root
+      | None -> "resources/wabbit_alpha.png"
+    in
+    load_texture path
+  in

We can also put this code in some helper library to avoid duplications.

So that we can run them with:

ROOT=examples/textures dune exec -- examples/textures/textures_bunnymark_ocaml_types.exe

What do you think?

[tjammer]

I share your sentiment, but I'm not convinced that typing ROOT=... is much more convenient than cd ....

What about this: When lauching with dune exec, the executables have their Sys.executable_name set to an absolute path. With that, we could get the resoure path like

  let respath res =
    if Filename.is_relative Sys.executable_name then res
    else Filename.(concat (dirname Sys.executable_name) res)
  in

It's not the most robust solution in the world but works for the examples, and saves typing out the directory all-together.