[Doxygen-develop] [Patch]: Added support for SVG graphics with dot

[Christian E. <ce...@gm...>]

Hello,

I've created a patch which adds support for generating Scaleable Vector Gr=
aphics instead 
of bitmaps (for HTML output).

Most today's browsers have at least limited support f=FCr rendering svg gr=
aphics. I got the 
best results with Opera, Konqueror is nearly Ok, Firefox has some work lef=
t...

SVG graphics are included with the <object></object> tag instead of <img>.=
 I got most 
information from SELFHTML (german only):

http://de.selfhtml.org/html/multimedia/objekte.htm#datendateien

For browsers which doens't support rendering SVG it's possible to show an =
alternative 
content (e.g. a png graphic). Thus my patch creates additional png (fixed)=
 graphics when 
the user selects svg.


Patch description (generated with 'svn diff'):
- config.l:
  o Added 'svg' item for DOT_IMAGE_FORMAT

- dot.h
  o Added prototype for getPngImageSize() (see open issues)

- dot.cpp
  o Implemented getPngImageSize() (see open issues)
  o Generate an additional png file if the user selected svg format
  o Include both files as mentioned in the above tutorial

- htmlvisitor.cpp:
  o Generate an additional png file if the user selected svg format
  o Include both files as mentioned in the above tutorial

I've tried to adopt the existing coding style as good as possible. There s=
hould be no 
additional changes than those mentioned above. If the user doesn't select =
the svg format, 
the patch shouldn't have any effects.


Open issues:
- Image size of the SVG graphics
It's not very straightforward to generate an svg file with the same image =
size compared to 
an equal bitmap file. For reasons I don't understand the dot tool uses dif=
ferent sizes for 
svg and png graphics. I've tried to change this by setting DPI to 96 in do=
t but the resulting 
graphic was not rendered correctly in most of my browsers.

So I've decided to get the destination size from the png file (which is al=
so created) and to 
scale the svg to this value. This possibly strange way produced the most a=
cceptable 
results.

- Hyperlinks in the SVG graphics
For resons I don't know (perhaps a bug), all hyperlinks in the doxygen gen=
erated dot files 
start with a '$' character. This char is also present in the generated map=
 file. I've never 
seen this before but it seems that it doesn't harm.
For svg graphics at least some browsers don't use the map file, they get i=
nformation about 
hyperlinks directly from the svg file. Dot also includes the $ from the do=
t file here. At least 
in this case, my browsers failed to follow the link until I removed the $ =
char. Maybe it 
would be the best to remove it at all.


regards
Christian