Issue 3710: draw:enhanced-path current point definition unclear.

[Regina Henschel <regina.henschel@libreoffice.org>]

Hi Patrick,

I'm working on issue 3710 and need some decisions. Please put issue 3710 
on the agenda. You can put it at last point. It is for ODF 1.4 and 
therefore not urgent.

https://issues.oasis-open.org/browse/OFFICE-3710

These are the observations

With the ExampleAB.odp you see

* draw nothing [PowerPoint]

* draw segment (5400|16200) to (10800|21600) [LibreOffice]

* draw segment (0|0) to (5400|16200) and segment (5400|16200) to 
(10800|21600) [Scribus]

* your application?

With the ExampleC.odp you see differences too:
* Scribus: similar to SVG, but without marker
* PowerPoint: A closed triangle left, without filling, the right part is 
missing, no marker
* LibreOffice: Left triangle closed, filled, with marker. Right part 
only with two segments, filled, with markers.
* your application?

The attached SVG-file has the same path as the enhanced-path in 
ExampleC.odp.

These are the underlying problems:

A Behavior for ill-structured path
----------------------------------
A1) If the path definition does not follow the specification, then the 
behavior is undefined.
A2) If the path definition does not follow the specification, then the 
consumer should draw those segments of the path, which are well defined. 
Example: In enhanced-path="L 5400 16200 10800 21600" a path segment from 
point (5400|16200) to point (10800|21600) is drawn. The first segment 
has no valid "current point" and so cannot be drawn. But it sets the 
"current point" (5400|16200) for the following segment.
A3) If the path definition does not follow the specification, the path 
is drawn from the beginning as long as it is valid. Segments after the 
first error are not drawn.

B "current point" at the begin of the path
------------------------------------------
B1) The "current point" is initially not defined.
B2) The "current point" is initialized to point (0|0).

C "current point" after Z command
---------------------------------
Text in ODF 1.2, "Close the current sub-path by drawing a straight line 
from the current point to current sub-path's initial point."
C1) The "current point" is not changed.
C2) The current sub-path's initial point becomes "current point". 
[definition in SVG]
C3) The current point is invalidated and no longer defined. (Further 
drawing in ExampleC depends on behavior for problem A)

Kind regards
Regina

Attachment: Example_withMarker.svg
Description: image/svg

Attachment: ExampleAB.odp
Description: application/vnd.oasis.opendocument.presentation

Attachment: ExampleC.odp
Description: application/vnd.oasis.opendocument.presentation