[Libreoffice-bugs] [Bug 125582] New: FILEOPEN PPTX follow path text transformation is different in LO and PowerPoint

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=125582

            Bug ID: 125582
           Summary: FILEOPEN PPTX follow path text transformation is
                    different in LO and PowerPoint
           Product: LibreOffice
           Version: 6.1.1.2 release
          Hardware: x86-64 (AMD64)
                OS: Windows (All)
            Status: UNCONFIRMED
          Severity: normal
          Priority: medium
         Component: Impress
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: rb.henschel at t-online.de

Created attachment 151764
  --> https://bugs.documentfoundation.org/attachment.cgi?id=151764&action=edit
Exampel ArchDown

Open one of the attached documents. The first slide contains the text transform
object, the second slide contains a screenshot from PowerPoint.

The differences are:
(1) PowerPoint puts the first or last line of the text on the path, LibreOffice
puts the middle of the text block on the path.
(2) PowerPoint uses a parallel line to the radius in regard to the circle as
alignment reference. LibreOffice uses a line perpendicular to the path through
the text reference point as alignment reference.

The OOXML standard has no suitable descriptions for the shape types
"textArchUp", "textArchDown", "textCircle" and "textButton". The ODF standard
is no help, because it has neither a description, how to render similar text
shapes. Therefore I suggest, that LibreOffice should try to render it the same
way as PowerPoint.

The way, the reference point of the text is calculated in PowerPoint is crazy.
>From my investigations I conclude this algorithm, see help lines in the
attached files:
(1)Draw a WordArt shape, e.g. width larger than height. Use numbers for
position and size.
(2)Draw a (red) ellipse with same position and size.
(3)Mark a (green) point A on the ellipse as position for the handle.
(4)Drag the handle of the WordArt shape to that point.
(5)Draw a circle with the same width and center as the ellipse.
(6)Draw a straight (blue) line from center through handle point A.
(7)Find the intersection of this line with the circle and name it point B.
(8)Draw a vertical straight (black) line through point B.
(9)Find the intersection of this line with the ellipse and name it point C.
That is the reference point for the text.
(10)Draw a straight line parallel to the line from step (6) through point C.
That is the alignment reference for the text lines.
[Depending on handle position it might be necessary to mirror some help lines
and points.]

This is a follow-up report to bug 116350, where the import of WortArt shapes
were implemented.

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