Writing is using language to convey meaning to a specific audience.
Activities that are writing:
- authoring a text
- texting
- preparing a speech
- composing music
Activities that aren’t writing:
- drawing
- painting
- sculpting
Although the above three things can convey meaning, In my opinion they aren’t a language.
I disagree on your exclusion of drawing because if you include older times when written language, which included words, was not used, drawing was their version of writing.
I agree with you here that what you define as not writing is not language, or at least spoken language. With the exception of sculpting I thing drawing and painting could be a type a writing because they may not use a language that we would talk to one another with but it does still use an unspoken language that creates maybe emotions or some reaction to it.