[SVG] Adds clip operator, fixes setGState, fill, stroke operators

[pramodhkp]

This PR:

• Adds support for 'clip' operator (Ref: http://www.jagpdf.org/doc/samples/jagpdf_doc_clipping_path.pdf, http://www.jagpdf.org/samples/imageclip.pdf or PDF 32000 spec document (Page 248) )
• Fixes setGState to accept args properly (Ref: /test/pdfs/extgstate.pdf)
• Added some missing properties for text & path element (Ref: /test/pdfs/txt2pdf.pdf)
• Fixed viewport transform to include translate (only scaling was done previously) (Ref: /test/pdfs/jai.pdf)
• Added eoFillStroke method (Ref: /test/pdfs/jai.pdf)

[pramodhkp]

cc @timvandermeij

[timvandermeij]

@pramodhkp I have added some review comments. Could you link one or two specific PDFs that are affected (i.e. render better) with this change?

[pramodhkp]

Ah, yeah. I meant to do that. I will add it after I make the changes. Thanks for the review.

[pramodhkp]

@timvandermeij I have made the changes. I also separated the changes in fillStroke method into a separate commit. I have updated the reference pdfs in the PR comment.

[timvandermeij]

@pramodhkp I can confirm that /test/pdfs/txt2pdf.pdf renders much better (the text color is correct now and the spheres are filled correctly). test/pdfs/extgstate.pdf seems to render worse for me compared to Acrobat and the version prior to this PR (i.e. the line is now two dots and the text is way too large). I could not verify the 'clip' operator change, because Tracemonkey shows no difference to me (I assume that's what you meant by 'default doc'; if you meant the document loaded by default in the SVG viewer example, than I cannot verify it because the text still renders crazily for me because of that Bugzilla bug).

I have also reviewed the code again and added two small comments. Overall, this is starting to look really good.

Below a screenshot of how extgstate.pdf renders before and after applying this PR. You can clearly see that the rendering became worse. Any idea what's causing that?

[pramodhkp]

@timvandermeij I am not sure what's wrong with the rendering of /test/pdfs/extgstate.pdf . I could not try it in adobe reader. But, I did try in Okular (KDE) and PDF.js (canvas), and it seemed to render similarly. The text font is courier and the sizes are also proper, I think.

As for the clippping, by default PDF, I meant the 'default' in SVG. (liveprogramming.pdf). Anyway, I think it's not a good example. I tried it on the PDF 32000 document, and I think the clip is still not working properly. For reference, it's Page No. 240 in that document.

[timvandermeij]

This is how Adobe Acrobat (and Adobe Reader for that matter) renders it:

So we have two different renderings for this file now: Adobe's rendering and PDF.js's canvas/your current PR rendering. Since your SVG rendering is now equal to PDF.js's rendering, I wouldn't worry about this file too much. PDF.js currently also renders it wrong compared to Adobe.

[yurydelendik]

nit: try to not use method call with different amount of parameters, e.g. make it this.clip('nonzero') and if needed use e.g. this.applyClip('nonzero')

[yurydelendik]

Really good, thank you.