bug#75224: RNG validation unnecessarily marks buffer as changed

[Vili Aapro]

Gentle people,

I found a bug in RNG Validation mode in the file `nxml/rng-valid.el' that 
unnecessarily marks buffer as changed.  The bug can be fixed with a simple 
application of `with-silent-modifications' in the function 
`rng-do-some-validation-1'.  I've attached a patch that does so.  However, in 
the long run, in my opinion the application of `with-silent-modifications' 
should be moved to `rng-clear-cached-state'; that is where it properly belongs. 
 Perhaps this has been left undone because of efficiency reasons; perhaps there 
is work to be done to make `with-silent-modifications' less expensive.

To reproduce, visit a big enough RNG-validatable XML file, such as the included 
`rdfxml.rng'; goto and end-tag, say on line 22; kill it; undo.

Undo runs `after-change-functions' and thus `rng-after-change-function' and 
thus `rng-do-some-validation-1', reproducing the bug.

Best regards and thank you,
Vili Aapro

0001-Fix-bug-in-rng-valid-that-unnecessarily-marks-buffer.patch
Description: Text Data

rdfxml.rng
Description: XML document