get-text-property error if narrowed

get-text-property error if narrowed

[Lennart Borgman (gmail)]

get-text-property signals an error if the position argument is outside a 
narrowed region. That is very inconvenient. It would be much better if 
it behaved like get-char-property which does not do this.

Re: get-text-property error if narrowed

[Richard Stallman]

    get-text-property signals an error if the position argument is outside a 
    narrowed region. That is very inconvenient. It would be much better if 
    it behaved like get-char-property which does not do this.

I just tried (get-char-property 1 'face) in my Rmail buffer and got an
error, so I think the two functions are alike in this regard.
I think that an error is the correct result in that case.
(buffer-substring also gives an error when the positions are out of range.)
Why do you think otherwise?

Is there a case in which get-char-property fails to give this error?

Re: get-text-property error if narrowed

[Lennart Borgman (gmail)]

Richard Stallman wrote:
>     get-text-property signals an error if the position argument is outside a 
>     narrowed region. That is very inconvenient. It would be much better if 
>     it behaved like get-char-property which does not do this.
> 
> I just tried (get-char-property 1 'face) in my Rmail buffer and got an
> error, so I think the two functions are alike in this regard.
> I think that an error is the correct result in that case.
> (buffer-substring also gives an error when the positions are out of range.)
> Why do you think otherwise?
> 
> Is there a case in which get-char-property fails to give this error?

I think it happens when there is a property on an overlay. 
get-char-property finds that and returns it. If there is no overlay with 
the tested property then I get an error. (Note that I am using a CVS 
version from 2007-06-04.)

Re: get-text-property error if narrowed

[Richard Stallman]

    I think it happens when there is a property on an overlay. 
    get-char-property finds that and returns it. If there is no overlay with 
    the tested property then I get an error. (Note that I am using a CVS 
    version from 2007-06-04.)

I think it is a bug not to get an error in that case.

However, you said you prefer that behavior.  Could you tell me why?

Re: get-text-property error if narrowed

[Lennart Borgman (gmail)]

Richard Stallman wrote:
>     I think it happens when there is a property on an overlay. 
>     get-char-property finds that and returns it. If there is no overlay with 
>     the tested property then I get an error. (Note that I am using a CVS 
>     version from 2007-06-04.)
> 
> I think it is a bug not to get an error in that case.
> 
> However, you said you prefer that behavior.  Could you tell me why?

It is just that I prefer consistency.

I made a mistake when I said that no error should be raised. It is 
clearly better to get an error since in many cases it would be a mistake 
to access a point outside the narrowed region.

Re: get-text-property error if narrowed

[Richard Stallman]

I made get-char-property give the proper error.
Thanks.

Re: get-text-property error if narrowed

[Richard Stallman]

    get-text-property signals an error if the position argument is outside a 
    narrowed region. That is very inconvenient. It would be much better if 
    it behaved like get-char-property which does not do this.

I just tried (get-char-property 1 'face) in my Rmail buffer and got an
error, so I think the two functions are alike in this regard.
I think that an error is the correct result in that case.
(buffer-substring also gives an error when the positions are out of range.)
Why do you think otherwise?

Is there a case in which get-char-property fails to give this error?