getTexture

pub fn getTexture(self: ImageSource) !Texture {
        const key = self.hash();
        const invalidate = switch (self) {
            .imageFile => |f| f.invalidation,
            .pixels => |px| px.invalidation,
            .pixelsPMA => |px| px.invalidation,
            // return texture directly
            .texture => |tex| return tex,
        };
        if (dvui.textureGetCached(key)) |cached_texture| {
            // if invalidate = always, we update the texture using updateImageSource for efficency, otherwise return the cached Texture
            if (invalidate == .always) {
                var tex_mut = cached_texture;
                try tex_mut.updateImageSource(self);
                if (cached_texture.ptr != tex_mut.ptr) {
                    // updateImageSource created a new texture, called
                    // destroyLater on old one, remove before adding new one
                    _ = dvui.currentWindow().texture_cache.remove(key);
                    dvui.textureAddToCache(key, tex_mut);
                }
                return tex_mut;
            } else return cached_texture;
        } else {
            // cache was empty we create a new Texture
            const new_texture = try Texture.fromImageSource(self);
            dvui.textureAddToCache(key, new_texture);
            return new_texture;
        }
    }