Re: Implementing SVG attribute "stroke-miterlimit" ( tdf#48066)

Hi Armin,

since yesterday I have thought about it. I now think, that I will use 
the GDI+ type 'LineJoinMiterClipped'. That makes rendering inside LO 
consistent and that is more important as interoperability with foreign 
applications. It is then still possible to implement the use of the GDI+ 
type 'LineJoinMiter' in addition later on, and use it for pptx.

It is not a problem of scaling, but the kind how the sharp corner is 
clipped is fundamental different.

If you think I should do it different, please tell me.

Next problem: When testing a curve I got bug
https://bugs.documentfoundation.org/show_bug.cgi?id=99165 Rendering of 
mitered curve changes with zoom level
That is independent of SVG, but effects the rendering of SVG too. Do you 
have a code pointer, where I should look for the reason?

The state is now, that I have finished the transport of 
fMiterMinimumAngle for Windows. The rendering is already good with 
decomposition and with anti-aliasing on as well, here on Windows. I have 
started to adapt the headers for the other OS. A MetaXYAction is still 
missing.

Kind regards
Regina

Armin Le Grand schrieb:
> Hi Regina,
>
> yes, the MiterLimits are different in different systems, but all are
> somehow specified using the angle between the two vectors involved. I
> remember to have seen some definitions, most using the same and 15 as
> default value. The ways to be compatible with MS are:
> - find a definition somewhere, mqaybe in forums or newsgroups (I have
> none, sorry)
> - reverse engineer by trying out. Probability is high that there is a
> (linear?) relationship between the values, so it might be a simple scaling
> HTH!
>
> Regards,
> Armin
>
> Am 07.04.2016 um 14:35 schrieb Regina Henschel:
> > Hi all,
> >
> > I have made some progress. But a new problem comes up.
> >
> > I have changed WinSalGraphicsImpl::drawPolyLine [3] so that it gets an
> > additional parameter fMiterMinimumAngle (same meaning as in
> > createAreaGeometryForJoin) and uses it for gdi+. The rendering in
> > edit-mode in Draw and Impress is correct then with gdi+ on Windows.
> > Even Text in SVG works out of the box. [BTW: The current rendering
> > using gdi+ is wrong, see my report bug#99102.]
> >
> > The behavior of gdi+ is described in [1]. To get the same kind of
> > behavior as in LO, when the miter limit is exceeded, the LineJoin type
> > 'LineJoinMiterClipped' has to be used.
> >
> > Being only in LibreOffice and SVG, that would be no problem. But MS
> > seems to use different defaults. The rendering in PowerPoint looks
> > like gdi+ type 'LineJoinMiter'. The specification for 'lim' in
> > ECMA-376, Part 1, chapter 20.1.8.43, has no details, and I have not
> > found details otherwhere.
> >
> > This gdi+ type 'LineJoinMiter' kind of clipping (see the image in the
> > article [1]) will be used in SVG 2 [2] too under the identifier
> > 'miter-clip'.
> >
> > So my question: Ignore interoperability with MS? If not, how to solve it?
> >
> > Kind regards
> > Regina
> >
> > [1]
> > https://msdn.microsoft.com/en-us/library/windows/desktop/ms534148%28v=vs.85%29.aspx
> >
> >
> > [2] https://www.w3.org/TR/svg-strokes/#StrokeShape
> >
> > [3]
> > diff --git a/vcl/win/gdi/gdiimpl.cxx b/vcl/win/gdi/gdiimpl.cxx
> > index 7febbe8..36ecb31 100644
> > --- a/vcl/win/gdi/gdiimpl.cxx
> > +++ b/vcl/win/gdi/gdiimpl.cxx
> > @@ -2031,7 +2031,8 @@ bool WinSalGraphicsImpl::drawPolyLine(
> >      double fTransparency,
> >      const basegfx::B2DVector& rLineWidths,
> >      basegfx::B2DLineJoin eLineJoin,
> > -    css::drawing::LineCap eLineCap)
> > +    css::drawing::LineCap eLineCap,
> > +    double fMiterMinimumAngle)
> >  {
> >      const sal_uInt32 nCount(rPolygon.count());
> >
> > @@ -2064,9 +2065,9 @@ bool WinSalGraphicsImpl::drawPolyLine(
> >              }
> >              case basegfx::B2DLineJoin::Miter :
> >              {
> > -                const Gdiplus::REAL aMiterLimit(15.0);
> > +                const Gdiplus::REAL
> > aMiterLimit(1/sin(fMiterMinimumAngle/2.0));
> > Gdiplus::DllExports::GdipSetPenMiterLimit(pTestPen, aMiterLimit);
> > -                Gdiplus::DllExports::GdipSetPenLineJoin(pTestPen,
> > Gdiplus::LineJoinMiter);
> > +                Gdiplus::DllExports::GdipSetPenLineJoin(pTestPen,
> > Gdiplus::LineJoinMiterClipped);
> >                  break;
> >              }
> >              case basegfx::B2DLineJoin::Round :
> >
> > _______________________________________________
> > LibreOffice mailing list
> > LibreOffice@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/libreoffice