- From: Jon Ferraiolo <jonf@adobe.com>
- Date: Mon, 23 Jan 2006 22:31:23 -0800
- To: "Rick" <graham.rick@gmail.com>, <www-svg@w3.org>
Hiya Rick! Your suggestion sounds good to me - the SVG spec should state how dash patterns are supposed to work on shapes such as circles and rectangles. I am not speaking officially for the working group, but my expectation is that the working group will agree with you and add appropriate language to the spec. The most natural thing would be to state in the description of each of the basic shapes how the dash patterns in stroke-dasharray must be applied. We have "path equivalents" in the spec for rect, line, polyline and polygon, which seems like the obvious method for those elements, but I agree that we need to come up with non-ambiguous rules for circle and ellipse. (I would think you would start at zero degrees and sweep in a mathematically "positive" rotate direction, where "positive" is treated in the same manner as SVG's transformations.) Jon -----Original Message----- From: www-svg-request@w3.org [mailto:www-svg-request@w3.org] On Behalf Of Rick Sent: Sunday, January 22, 2006 8:03 PM To: www-svg@w3.org Subject: [SVG12] Issues regarding stroke-dasharray Dear SVG working group, Thank you for your hard work in resolving issues on this CR. This is an issue that I've been aware of this for quite some time, but had forgotten. Please forgive me for leaving it to this late date to bring it up. Dash arrays can have a dramatic effect on the look of an image, particularly if they are large. I'm currently working on a technical proposal that involves the use of SVG and have some compatibility problems between major viewers over this feature. The description of dasharray http://www.w3.org/TR/SVG/painting.html#StrokeProperties does not specify in what manner the effect should be applied. This is particularly esoteric with closed shapes such as rect or circle because they have no intrinsic starting point or direction. The spec does outline how these objects are to be described, but it does not specify that dashed lines must follow these rules. There are inconsistencies in current implementations in this respect that produce drastically different results for some markup. I would suggest appending wording similar to the following to the description of dasharray to assist implementers with this feature: --- The dash sequence must start at the beginning of a shapes data and follow the stroke description through to the end of the shape. For shapes that do not have obvious starting points, the method for rendering them is specified in the basic shapes section of this specification. <link> --- Please revise the specification to clarify this. Further to this issue, I believe that the methods for describing of circles and ellipses needs further clarification. http://www.w3.org/TR/SVG/shapes.html#CircleElement states: --- The arc of a 'circle' element begins at the "3 o'clock" point on the radius and progresses towards the "9 o'clock" point. The starting point and direction of the arc are affected by the user space transform in the same manner as the geometry of the element. --- It is unclear whether, unaffected by any transformation, that the direction of these shapes should be clockwise or counterclockwise. 3 o'clock and 9 o'clock are 180 degrees from each other. I would suggest changing the wording so that 9 o'clock be changed to either 12 o'clock or 6 o'clock, or that a CW or CCW direction be specified. Please revise the descriptions of the circle and ellipse elements to clarify this. -- Cheers! Rick
Received on Tuesday, 24 January 2006 06:32:18 UTC