Text-Properties and read-only

Text-Properties and read-only

[Mario Domgörgen]

Hey group!

My point is between a read-only character and the end of the buffer and
"(get-text-property (point) 'read-only)" resulted in nil, but if i try
to overwrite that character i get "Text is read-only"?! Very strange...

Any idea?

Mario

-- 
A file that big?
It might be very useful.
But now it is gone.

Re: Text-Properties and read-only

[Stefan Monnier]

>>>>> "Mario" == Mario Domgörgen <kanaldrache@gmx.de> writes:
> My point is between a read-only character and the end of the buffer and
> "(get-text-property (point) 'read-only)" resulted in nil, but if i try
> to overwrite that character i get "Text is read-only"?! Very strange...

That's because of the subtleties of boundary conditions.
Text-properties apply to characters, so (get-text-property (point)
'read-only) gives you the text-property of the char after position (point)
(which in your case doesn't exist and is by convention defined to not have
any property.  It could/should signal an error instead).

So what is the value of the read-only property "at point" (i.e. between
the char before point and the char after point) ?  Well it depends on the
property before point and the property after point and the stickiness of
that property: a property can be front-sticky and/or rear-sticky.

By default properties are rear-sticky which means that a char inserted
after such a property will inherit it.  `read-only' is like that.
So in your case, the read-only property between the char before point
and the (non-existent) char after point is non-nil because it's inherited
from the char before point.


        Stefan