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Re: marker improvements

From: Cyril Concolato <cyril.concolato@telecom-paristech.fr>
Date: Thu, 31 May 2012 21:36:44 +0200 (CEST)
To: Cameron McCormack <cam@mcc.id.au>
Cc: SVG public list <www-svg@w3.org>
Message-ID: <48731d8d-1cd0-4f14-ae97-eef2a84ef79f@zmail120>
Hi Cameron,

Quick comment. The spec has the notion of 'markable' element. It lists some graphical elements but not others like ellipse, circle, rectangle. I think we have a resolution to define the exact stroking for those elements, so we could add them to the list of markable elements, no?

Cyril

----- Mail original -----
De: "Cameron McCormack" <cam@mcc.id.au>
À: "SVG public list" <www-svg@w3.org>
Envoyé: Samedi 26 Mai 2012 09:26:54
Objet: marker improvements

I've added some of the marker improvement proposals that we discussed 
recently to the spec, although I have changed them a bit.  Instead of 
extending marker-mid to allow specifying a pattern of markers to place 
along the path, not at vertices, I added a separate property for this. 
I also added a separate property for markers at the centre of path 
segments.  marker-start, marker-mid and marker-end remain unchanged.

marker-segment:

   https://svgwg.org/svg2-draft/painting.html#SegmentMarkers

marker-pattern:

   https://svgwg.org/svg2-draft/painting.html#RepeatingMarkers

The expanded marker shorthand that allows setting marker-{start,mid,
end,segment,pattern} at once, with different values:

   https://svgwg.org/svg2-draft/painting.html#RepeatingMarkers

There's some updated text at the start of the section with an overview 
of the different types of markers:

   https://svgwg.org/svg2-draft/painting.html#Markers

I extended the <marker> element like we discussed to allow it as a child 
of a <path> etc. element.  That's a "positioned marker".


For setting back the stroke to allow better arrowheads, and to have say 
circular hollow markers without the stroke showing through, I added a 
half baked proposal to stimulate some discussion:

   https://svgwg.org/svg2-draft/painting.html#MarkerKnockout

Look at the image for an overview without having to read all that dense 
text in there.

I went a bit crazy on the shapes, perhaps, but the key thing I was 
trying to avoid was allowing a generic path to be specified, since that 
would require some difficult intersection checking.  At least with these 
predefined shapes the number of edges to check for intersections is low 
and known.

But as I mention in the ISSUE in that section, using this feature for 
some cooler looking dash patterns (dashes looking like chevrons for 
example) you probably want to put the two sides of the shape at 
different orientations along the path, and that again requires more 
difficult shape/intersection calculations.

Anyway, comments welcome.
Received on Thursday, 31 May 2012 19:37:12 GMT

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