Currently, GpuTexture2DHandle is defined as:

pub struct GpuTexture2DHandle(Option<GpuTexture>);

impl GpuTexture2DHandle {
    pub fn invalid() -> Self {
        Self(None)
    }
}

GpuTexture2DHandle::invalid is almost never used (and its one use can be easily refactored away), but it causes a lot of headache. In particular, TextureManager2D::get can fail, because of this invalid state.

In other words, I'd like to get rid of GpuTexture2DHandle and just use GpuTexture everywhere.