Loading Textures with SDL for use with OpenGL

[zedseven]

Apologies if this is a dumb question, but I'm using SDL for window management and OpenGL for rendering, and I want to use SDL for texture loading rather than adding another dependency for something SDL is already capable of.

I know I should be able to use Texture.gl_bind_texture() to actually use the texture, but how can I load the texture in the first place if it requires a TextureCreator which in turn requires a Canvas? Would I really need to create a canvas I'm not going to use in order to accomplish this, or am I missing something?

I found mention of this here which makes me think it's possible, but I'm not sure how to accomplish it:

I am just using SDL2 to manage the window and the textures, while all the rendering is done with my own renderer that is using OpenGL ES 2 with no SDL2 involved at that stage except for retrieving the handle to the actual texture.

Again sorry if it's not a great question - it's just difficult finding documentation for this specific combination.

[Cobrand]

So I only know the theory but I haven't actually used gl_bind_texture myself.

In short it depends what you mean by "rendering".

A Canvas is necessary to create a Texture, because texture does not make sense without one. It's simply a pointer to a specific implementation of hardware-accelerated texture inside your graphic card (so OpenGL texture, DirectX texture, ...). You can't just load a Texture by itself, because without a Canvas it doesn't know what backend to target.

If your "rendering" part is simply your custom vertex/fragment shaders, then you can initialize a Canvas via SDL2, then use TextureCreator to create textures, call gl_bind_texture whenever necessary and it should mostly work. I think you are "tied" to whatever version of OpenGL SDL2 uses for you, but you may have ways to configure that via https://docs.rs/sdl2/0.34.5/sdl2/video/gl_attr/index.html .

If you absolutely want to initialize your context then use a Canvas on top of that, then I don't think it is possible.

But honestly this is thin ice, I would advise you to simply not bother with the rendering side of SDL2 if you already have your implementation, and use a crate like image for texture loading, if you already know OpenGL with ~50 lines of code you can make something basic that still works very well.

Hope that helped.

[zedseven]

That makes sense, thank you.

I think I'll take that advice and use something else to load the textures - it's not worth the trouble to slightly cut down on dependencies.