Maybe Unsound in init_image

[lwz23]

Hello, thank you for your contribution in this project, I am scanning the unsoundness problem in rust project.
I notice the following code:

pub fn init_image(sgimage: sg_image, data: *const u8, size: usize) {
        let mut width: i32 = 0;
        let mut height: i32 = 0;
        let mut channels: i32 = 0;
        let image_data = unsafe {
            // Converts from PNG format to RGBA8 format
            stbi_load_from_memory(data as *const u8, size as core::ffi::c_int, &mut width, &mut height, &mut channels, 0)
        };
        let image_desc = sg::ImageDesc {
            width,
            height,
            pixel_format: sg::PixelFormat::Rgba8,
            data: sg::ImageData {
                subimage: [[sg::Range { ptr: image_data as *const core::ffi::c_void, size: (width * height * 4) as usize }; 16]; 6],
                ..Default::default()
            },
            ..Default::default()
        };

        sg::init_image(sg::Image { id: sgimage.id }, &image_desc);

        unsafe { stbi_image_free(image_data as *mut core::ffi::c_void) };
    }

Considering that pub mod render_2d, and init_image is also a pub function. I assume that users can directly call this function. This potential situation could result in stbi_load_from_memory(data as *const u8, size as core::ffi::c_int, &mut width, &mut height, &mut channels, 0) being operating on a null pointer, I guess it might trigger undefined behavior (UB). For safety reasons, I felt it necessary to report this issue. If you have performed checks elsewhere that ensure this is safe, please don’t take offense at my raising this issue.
I suggest Several possible fixes:

1. If there is no external usage for init_image, it should not marked as pub.
2. init_image method should add additional check for null pointer.
3. mark init_image method as unsafe and proper doc to let users know that they should provide valid Pointers.

[lwz23]

ping

[troyedwardsjr]

@lwz23 Yes apologies, I'll take a look at this, thanks for the heads up! I've been busy prioritizing the WASM component model overhaul which has just been merged in: #6

Much of the rendering code remains the same though.

There will be lots of improvements to the renderer in the future, including a 3D API.