- From: L. David Baron <dbaron@dbaron.org>
- Date: Tue, 10 Jun 2008 15:07:55 -0700
- To: www-style@w3.org
CSS 2.1 added the following text: # The computed value of "font-weight" is either: # # * one of the legal number values, or # * one of the legal number values combined with one or more of # the relative values (bolder or lighter). This type of # computed values is necessary to use when the font in # question does not have all weight variations that are # needed. http://www.w3.org/TR/2007/CR-CSS21-20070719/fonts.html#font-boldness This text doesn't say what specified values lead to these computed values. It is, in fact, ambiguous, and could lead to two different sets of results, as explained below. I believe it should either: (1) make the following points normatively: * the computed value is a legal number value combined with an <em>ordered sequence</em> of relative values. * when the specified value is a value other than 'bolder' or 'lighter', the computed value is the same as the specified value (perhaps normalized) * when the specified value is 'bolder' or 'lighter', the computed value is the inherited value with the 'bolder' or 'lighter' appended to the ordered sequence of relative values. or (2) make the following points normatively: * the computed value is a legal number value combined with a count of relative values (with positive vs. negative distinguishing bolder and lighter) * when the specified value is a value other than 'bolder' or 'lighter', the computed value is the same as the specified value (perhaps normalized) * when the specified value is 'bolder' or 'lighter', the computed value is the inherited value with the count incremented or decremented based on whether the value was 'bolder' or 'lighter' I think option (2) may agree more with the text I proposed removing in http://lists.w3.org/Archives/Public/www-style/2008Jun/0147.html . Then, it should give the following example (using real text, the license plate prefix expected on legitimate taxis in Beijing): # The following example demonstrates why the relative values must # be stored in an ordered sequence (and why opposite pairs cannot # be collapsed). Consider the following markup: # # <div style="font-weight: 700"> # <em style="font-weight: bolder"> # <span style="font-weight: lighter"> # 京B # </span> # </em> # </div> # # Suppose that one of the characters in the text is available only # in a font-family that has weights 400, 700, and 900. In this family, # starting from weight 700, bolder yields weight 900, and lighter # yields weight 700, causing the chacter to be displayed using the # face with weight 700. # # Now, suppose that the other character in the text is available # only in a font-family that has weights 400 and 700. In this # family, starting from weight 700, bolder has no place to go ... and finish by explaining how the choice of (1) or (2) above affects the result (whether the character ends up weight 700 (option 2) or weight 400 (option 1). -David -- L. David Baron http://dbaron.org/ Mozilla Corporation http://www.mozilla.com/
Received on Tuesday, 10 June 2008 22:08:30 UTC