[Libreoffice-bugs] [Bug 113449] New: numerical inconsistency in basegfx::utils::isInside() causes wrong clipping in PDF export

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=113449

            Bug ID: 113449
           Summary: numerical inconsistency in basegfx::utils::isInside()
                    causes wrong clipping in PDF export
           Product: LibreOffice
           Version: 6.0.0.0.alpha0+ Master
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Keywords: filter:pdf
          Severity: normal
          Priority: medium
         Component: graphics stack
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: mstahl at redhat.com
                CC: Armin.Le.Grand at me.com

exporting the LO conference 2017 template to PDF results in wrong clipping on
the Agenda page: there should be a vertical clip of the green group shape on
the left, but the actual result is an un-clipped shape that extends into the
text box as a triangle.

the PDF should contain this on the 2nd shape exported from drawPolyPolygon:
 0 0 307.5 595.2 re
 +W* n

but it's missing because the m_aClipRegion is empty at that point, because
intersectClipRegion of these PolyPolygons results in [0:], i.e. empty:

%  XXX aOld [1:<4:(0,0)--(3075.02,0)--(3075.02,5952.76)--(0,5952.76)>]
%  XXX aRegion
[1:<4:(-1276.72,-62.0787)--(3075.02,-62.0787)--(3075.02,6108.38)--(-1276.72,6108.38)>]

this is because of an inconsistency in basegfx::utils::isInside()
where isPointOnPolygon returns false (so it's not on the edge)
but then bCompXA is also false (because it's detected as equal to the edge),
so the isInside() wrongly returns false.

the problem is caused by a tiny difference in X,
3075.0236220472434 vs 3075.0236220472439

involved objects:

(rr) p *rCandidate.mpPolygon.m_pimpl
$33 = {
  m_value = {
    maPoints = {
      maVector = std::__debug::vector of length 4, capacity 4 = {{
          <basegfx::B2DPoint> = {
            <basegfx::B2DTuple> = {
              mfX = -1276.724409448819,
              mfY = -62.078740157480311
            }, <No data fields>}, <No data fields>}, {
          <basegfx::B2DPoint> = {
            <basegfx::B2DTuple> = {
              mfX = 3075.0236220472439,
              mfY = -62.078740157480311
            }, <No data fields>}, <No data fields>}, {
          <basegfx::B2DPoint> = {
            <basegfx::B2DTuple> = {
              mfX = 3075.0236220472439,
              mfY = 6108.3779527559054
            }, <No data fields>}, <No data fields>}, {
          <basegfx::B2DPoint> = {
            <basegfx::B2DTuple> = {
              mfX = -1276.724409448819,
              mfY = 6108.3779527559054
            }, <No data fields>}, <No data fields>}}
    },
    mpControlVector = std::unique_ptr<ControlVectorArray2D> containing 0x0,
    mpBufferedData = std::unique_ptr<ImplBufferedData> containing 0x7eee920,
    mbIsClosed = true
  }, 
  m_ref_count = 5
}

(rr) p aCurrentPoint
$40 = {
  <basegfx::B2DTuple> = {
    mfX = 3075.0236220472439,
    mfY = 6108.3779527559054
  }, <No data fields>}
(rr) p aPreviousPoint
$41 = {
  <basegfx::B2DTuple> = {
    mfX = 3075.0236220472439,
    mfY = -62.078740157480311
  }, <No data fields>}

(rr) p rPoint
$34 = (const basegfx::B2DPoint &) @0x7ffcc8ab2af0: {
  <basegfx::B2DTuple> = {
    mfX = 3075.0236220472434,
    mfY = 0
  }, <No data fields>}



the PDF export changed with commit 581806182ac7da81115c9675b4e828688178aa04
but it was differently wrong before that commit, the particular shape in the
group shape was missing completely, and there is no problem with the commit.

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