A simple Initialization texture binding function would be nice to have

[trace-andreason]

When I'm using sokol fetch to get a texture, I need to initialize the texture first with a placeholder texture. If you don't initialize the texture, because fetch won't finish on the first frame, your program crashes. It would be nice to have a function like this so everyone doesn't have to roll their own temporary texture binding function: https://github.com/zeromake/learnopengl-examples/blob/master/libs/sokol/sokol_helper.h

I'm working in zig, so I just wrote this:

fn dummyImage(textureSlot: u8) void {
    const data: [4]u8 = .{ 0, 0, 0, 0 };
    var img_desc: sg.ImageDesc = .{ .width = 1, .height = 1, .pixel_format = .RGBA8 };
    img_desc.data.subimage[0][0] = .{
        .ptr = &data,
        .size = 4,
    };
    state.bind.fs.images[textureSlot] = sg.makeImage(img_desc);
}

So its definitely not hard to work around, but I think that if everyone is going to need to do this when using fetch for textures, it might be good to have a more canonical solution to this problem.

[floooh]

Ah I see. You don't actually need to do that.

You can create the texture in two steps like I do here in the loadpng-sapp sample:

• first in the init-callback, call sg.allocImage() which "pre-allocates" an image object handle without an actual texture object behind it: https://github.com/floooh/sokol-samples/blob/7b85538bb974eecb12027db9b5e66f274797461a/sapp/loadpng-sapp.c#L61-L66

• in the per-frame code, you can simply use this handle as if it would be a valid image, sokol-gfx will skip any draw calls with invalid handles: https://github.com/floooh/sokol-samples/blob/7b85538bb974eecb12027db9b5e66f274797461a/sapp/loadpng-sapp.c#L195-L224

• in the fetch callback, call sg.initImage() to complete the image creation, this takes the handle from the allocImage() call, and the usual sg.ImageDesc struct: https://github.com/floooh/sokol-samples/blob/7b85538bb974eecb12027db9b5e66f274797461a/sapp/loadpng-sapp.c#L175-L184

...next time the frame callback is called, the image handle will be valid and rendering works as expected.

The vanilla sg.makeImage() function is basically alloc + init in the same call.

You can also explicitly skip rendering by testing if the image is valid, smth like:

if (sg.queryImageState(img) == .VALID) {
    // image has been initialized and it's valid to render
} else {
    // image still loading, or failed to load
}

...theoretically the same works for all resource types, but is mainly intended for images and buffers.

Also see this documentation blurb: https://github.com/floooh/sokol/blob/c2d01bc25c58be460787d5f027eed73d1c036e6f/sokol_gfx.h#L1276-L1437

[trace-andreason]

Ah ok, makes sense. Interesting in the openGL examples I'm working from they actually have the same comment copied from that example presumably. Wonder why they felt the need to define a header 🤔

[floooh]

Tbf the two-step initialization and deinitialization of sokol-gfx resource objects isn't a prominent feature, and also had some inconsistencies until sometime last year.