bug#62713: 29.0.60; DocView shows wrong conversion indicator when configured to use svg images

[Visuwesh]

[திங்கள் செப்டம்பர் 25, 2023] Visuwesh wrote:

> It is better solved by writing a separate pdf->svg converter function.
> Right now, the svg conversion is tacked on top of pdf->png converter
> function used for MuPDF.  This was done because I thought only MuPDF
> supported pdf->svg conversion but later I was informed that poppler has
> utilities to do too.

And looks like the poppler utility pdftocairo does not work the doc-view
expects it to when generating svg images.  AFAICT, there is no way to
make pdftocairo to generate a svg image per page like other tools do.  I
cannot loop either as there is also no way to know the number of pages
beforehand.  The png function also has hacks since pdftocairo is not
cooperative, and changing doc-view to not use
doc-view--image-file-pattern does not seem to be easy.  I attach the
patch named "doc-view-general-svg-wip.patch" which has my WIP and it
works just fine for MuPDF.

This particular problem can be easily solved by the following simple
patch instead:

diff --git a/lisp/doc-view.el b/lisp/doc-view.el
index b856b09c8b7..c0d27bdc68a 100644
--- a/lisp/doc-view.el
+++ b/lisp/doc-view.el
@@ -1283,7 +1283,8 @@ doc-view-pdf->png-converter-mupdf
                                     (expand-file-name
                                      doc-view-epub-user-stylesheet)))))))
     (doc-view-start-process
-     "pdf->png" doc-view-pdfdraw-program
+     (concat "pdf->" (symbol-name doc-view--image-type))
+     doc-view-pdfdraw-program
      `(,@(doc-view-pdfdraw-program-subcommand)
        ,@options
        ,pdf

But if you say we don't bother about pdftocairo support and implement
the generic support system, I can prepare a patch without the pdftocairo
stuff, and add some documentation to aid the users to write custom
converter functions.

doc-view-general-svg-wip.patch
Description: Text Data