- From: Peter <peter@strings.net>
- Date: Tue, 1 May 2001 17:01:26 -0700
- To: <www-svg@w3.org>
Thanks a bunch that helped, even though I dont see a reason why did they decide to do it the harder way and define the text chunk only if absolute coordinates are given :(what about the combination of dx,y or dy, x?) Also is there a more detailed definition on "textLength" ? -peter -----Original Message----- From: Jon Ferraiolo [mailto:jferraio@Adobe.COM] Sent: Monday, April 30, 2001 9:29 AM To: Peter Cc: www-svg@w3.org Subject: Re: textLength and text-anchor question... Peter, There are a couple of things going on here. First off, this might seem non-intuitive, but according to the SVG specification, the 'text-anchor' property setting on your 'tspan' element has no effect. If you read the description of 'text-anchor' (http://www.w3.org/TR/SVG/text.html#TextAnchorProperty), it says: ------------------ The 'text-anchor' property is applied to each individual text chunk within a given 'text' element. Each text chunk has an initial current text position, which represents the point in the user coordinate system resulting from (depending on context) application of the x and y attributes on the 'text' element, any x or y attribute values on a 'tspan', 'tref' or 'altGlyph' element assigned explicitly to the first rendered character in a text chunk, or determination of the initial current text position for a 'textPath' element. ------------------ The term 'text chunk' is defined in section 10.7.1 (http://www.w3.org/TR/SVG/text.html#TextChunks). Here is an excerpt: ------------------ Adjustments to the current text position are either absolute position adjustments or relative position adjustments. An absolute position adjustment occurs in the following circumstances: * At the start of a 'text' element * At the start of each 'textPath' element * For each character within a 'text', 'tspan', 'tref' and 'altGlyph' element which has an x or y attribute value assigned to it explicitly All other position adjustments to the current text position are relative position adjustments. Each absolute position adjustment defines a new text chunk. Absolute position adjustments impact text layout in the following ways: * Ligatures only occur when a set of characters which might map to a ligature are all in the same text chunk. * Each text chunk represents a separate block of text for alignment due to 'text-anchor' property values. * Reordering of characters due to bidirectionality only occurs within a text chunk. Reordering does not happen across text chunks. ------------------ Therefore, since the 'tspan' does not set an absolute position, it does not define a new text chunk, and therefore the 'text-anchor' property does not have any effect. The second part has to do with an error in the DTD in the Nov. 2 CR specification. The 'text-anchor' property was included in entity PresentationAttributes-TextElements, whereas it should have instead been included in entity PresentationAttributes-TextContentElements. Because of this error in the DTD and because Adobe implemented the DTD carefully, even if you make the 'tspan' into a separate text chunk by assigning an 'x' or 'y' attribute, the Adobe SVG Viewer version 2.0 will not support a 'text-anchor' **attribute** on a 'tspan' element. It will, however, support the 'text-anchor' property within a 'style' attribute (e.g., style='text-anchor:start'). We will fix the DTD and future versions of the Adobe SVG Viewer are likely to include the corresponding code fix. Jon Ferraiolo SVG Editor jferraio@adobe.com At 04:07 PM 4/29/01 -0700, Peter wrote: >Hello, > >I have 2 questions regarding proper text and tspan implementations. >Question 1: > How is "textLength" supposed to be calculated (w3c specs dont show >any formula) e.g. are character widths multiplied by font size when added >together with kerning and other spacing attributes? > >Question 2: > What is the right implementation of "text-anchor" within "tspan"? >According to W3C specs: >"The 'text-anchor' property is applied to each individual text chunk within >a given 'text' element. Each text chunk has an initial current text >position, which represents the point in the user coordinate system resulting >from (depending on context) application of the x and y attributes on the >'text' element, any x or y attribute values on a 'tspan', 'tref' or >'altGlyph' element assigned explicitly to the first rendered character in a >text chunk, or determination of the initial current text position for a >'textPath' element." > >Thus the svg below should render text "Text2" over "Text1", however >according to Adobe SVG viewer 2.0 (build 55) which supposedly has all >text-anchor features implemented, it renders "Text2" right after "Text1" >(effectively ingoring text-anchor attrib). Am I missing something? > > <text x="200" y="50">Text1 > <tspan text-anchor="end">Text2</tspan></text> > > >Thanks for your help. >-peter
Received on Tuesday, 1 May 2001 20:02:15 UTC