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SVGT 1.2 Tests: paint-stroke-205-t assumptions wrong?

From: Kalle Raita <kraita@nvidia.com>
Date: Fri, 25 Apr 2008 11:12:18 +0200
Message-ID: <85DD8D3F1695004A8A9A5AC16CE584BE06B836E3@deemmail01.nvidia.com>
To: <www-svg@w3.org>

Hi All,
 
I think that the test paint-stroke-205-t has some wrong assumptions. The
test is about
caps on zero length sub-paths. 

Implementation notes [1] says that the in the case of not finding a
non-zero
length segment in the subpath, default tangent of (1, 0) is used.

In the test paint-stroke, the reference paths seem to assume (1, 1)
default tangent. 
I cannot find any rotation transforms in the test content that would
explain the 
difference.

As a specific example, let's take a segment starting at line 141 of the 
test case file.
<path d="M200,200L300,300M399.99,399.99L400.01,400.01M500,300L600,250"
      stroke="red"
      stroke-width="48">
  <title>Red comparison - if visible - error</title>
</path>
<path d="M200,200L300,300M400,400ZM500,300L600,250"
      stroke="blue"
      stroke-width="50">
  <title>Blue testcase covers all red if correct</title>
</path>

The blue test path moves to (400,400) and immediately closes the
subpath. 
The subpath does not contain any segments with non-zero length, i.e., 
the default tangent is used. The red reference moves to (399.99,399.99) 
and draws line to (400.01, 400.01), generating a tangent with direction
(1,1), which contradicts the spec request to align "with the positive 
x-axis in user space". 
 
As a side note, the test case could be split over multiple files to make

it easier to map the SVG content to shapes on the screen.

[1]
http://www.w3.org/TR/SVGMobile12/implnote.html#PathElementImplementation
Notes

Yours,
   - Kalle Raita
 

Kalle Raita 
NVIDIA Corporation 
Tel. +358 40 723 1441 
kraita@nvidia.com 
http://eu.nvidia.com <http://eu.nvidia.com/>  

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Received on Friday, 25 April 2008 09:13:55 GMT

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