zscript-doc/api/drawing/TextureID.md

TextureID

Texture IDs can be explicitly converted to integers, but not the other way around. You can add and subtract integers with a textureid, however. (This only works with the integer on the right hand side.)

struct TextureID
{
   bool Exists() const;
   bool IsNull() const;
   bool IsValid() const;
   void SetInvalid();
   void SetNull();
}

Exists

Checks if the texture exists within the texture manager at all.

IsNull

Checks if the texture is the null index (0.)

IsValid

Checks if the texture index is not the invalid index (-1.)

SetInvalid

Sets the texture index to -1.

SetNull

Sets the texture index to 0.

The proper way to zero-initialize a textureid is:

textureid tex;
tex.SetNull();