Compilation mode very slow with large files

Compilation mode very slow with large files

[Giuseppe Scelsi]

Hi,

In Emacs 22.1.1 for Windows, when I open a large text file (15 MB) in
fundamental mode and then switch to compilation mode, emacs hangs for
ever, while the status bar displays "Fontifying <filename>...".  I tried
to set '`global-font-lock-mode' to nil, with no success.

Hitting C-g manages to stop the process, but the buffer is left with no
fontification or hot links, in spite of reading '(Compilation)' in the
status bar.

I tried using 'debug-on-entry' and stepping through the code, but this
causes no apparent change in the buffer in spite of the process
terminating successfully with no error messages.

Is this a bug or an expected behaviour?  Does anyone have a suggestion
on how to work around this?  Or any hint about to further debug the
problem?  I am really interested in getting the active click-on links to
the relevant lines of source code, I wouldn't mind if fontification were
switched off.

Thanks in advance.

Giuseppe

Re: Compilation mode very slow with large files

[Stefan Monnier]

> In Emacs 22.1.1 for Windows, when I open a large text file (15 MB) in
> fundamental mode and then switch to compilation mode, emacs hangs for
> ever, while the status bar displays "Fontifying <filename>...".

Yes.  This is expected.  Could explain why you're doing this?


        Stefan


PS: As for why this is; compilation-mode uses font-lock internally, so
turning off global-font-lock-mode doesn't help because compilation-mode
forces it back on anyway; furthermore compilation-mode needs font-lock
to work "top-to-bottom" rather than "first treat the part that's
displayed", so it disables jit-lock, thus causing the whole buffer to be
fontified at start.

Re: Compilation mode very slow with large files

[Giuseppe Scelsi]

Stefan,

The reason I am doing this is to analyse build logs produced in the
past.  It is very useful to be able to click on an error and jump
straight to the source code.  Is there any way I could do this other
than through the compilation mode (and writing my own lisp code)?

Giuseppe

----

> > In Emacs 22.1.1 for Windows, when I open a large text file (15 MB) in
> > fundamental mode and then switch to compilation mode, emacs hangs for
> > ever, while the status bar displays "Fontifying <filename>...".
>
> Yes.  This is expected.  Could explain why you're doing this?
>
>
>         Stefan
>
>
> PS: As for why this is; compilation-mode uses font-lock internally, so
> turning off global-font-lock-mode doesn't help because compilation-mode
> forces it back on anyway; furthermore compilation-mode needs font-lock
> to work "top-to-bottom" rather than "first treat the part that's
> displayed", so it disables jit-lock, thus causing the whole buffer to be
> fontified at start.

Re: Compilation mode very slow with large files

[Stefan Monnier]

> The reason I am doing this is to analyse build logs produced in
> the past.

That makes sense.

> It is very useful to be able to click on an error and jump
> straight to the source code.  Is there any way I could do this other
> than through the compilation mode (and writing my own lisp code)?

You should be able to force compilation-mode to use jit-lock (which
should fix your problems), tho I'm not sure how.

Maybe

  (require 'compile)
  (add-hook 'compilation-turn-on-font-lock
            (lambda () (kill-local-variable 'font-lock-support-mode)))

100% guaranteed untested,


        Stefan


PS: jit-lock will introduce various problems, such as the fact that
C-x ` may incorrectly tell you there's no more errors.  Or the fact that
directory change messages may not be obeyed.