Re: Doc-view fonts

[Stefan Monnier]

> Do emacs' "display system" and Doc-view mode refer to the same thing? 

doc-view is a simply major mode to look at PDF files.  All the rendering
is done by ghostscript rather than by Emacs (Emacs merely displays the
images generated by ghostscript).

>   a) Because I'm viewing a PNG, I can't select text in it for
>   pasting. So is Doc-view mode merely for passive reading of a text?

Yes, pretty much.  Doing anything more sophisticated (like being able
to select text) would involve a lot more work than the 60KB of
doc-view.el.

>   b) But apparently it is not for that either: the non-anti-aliased font
>   used to build the image of the text is very diffiult to read. So just
>   what is Doc-view mode for?

That depends on your ghostscript setup, it seems.  For me, the
anti-aliasing works OK (often a bit less well than xpdf, occasionally
slightly better, but usually sufficiently good for my eyes).

>   c) There is no message indicating that a PDF can't be displayed
>   because it is broken, but only a hang of the conversion process. 

Sounds like a bug.  If you can reproduce it, please M-x report-emacs-bug
showing how to reproduce it, starting from "emacs -Q".

> Or are all my difficulties because I'm not making proper use of
> Doc-view or have left something out that would make it useful?

doc-view is not a replacement for xpdf.  It would be good if it were,
but it seems unlikely to happen in the foreseeable future.  FWIW, I do
use it despite its shortcomings and for the following reasons reasons
(which are really shortcomings of xpdf and all other PDF viewers I've
tried until now):
- I can adjust the scaling and centering so that all the margins are
  outside of the Emacs window rather than wasting screen real-estate,
  and (that's the crucial bit), I can flip from page to page without
  having to recenter the page (all other PDF viewers insist on placing
  me back at the upper left corner of the page every time I switch to
  another page).
- I can quickly open another Emacs window displaying the same buffer,
  which lets me display several pages of the same document.
- (Once the document is completely rendered to PNG images) I find that
  doc-view mode is often faster at flipping pages than other PDF viewers.

  
        Stefan