- From: Nigel Megitt via GitHub <sysbot+gh@w3.org>
- Date: Thu, 03 Mar 2016 15:04:08 +0000
- To: public-tt@w3.org
nigelmegitt has just created a new issue for https://github.com/w3c/ttml2: == Ways to make span background height be lineHeight == Many (most?) CSS implementations draw the background box behind inline areas with a height less than the line height, meaning that successive lines are drawn with gaps between their background areas, if there's no block level background color set. We want to be able to avoid that situation, since it negatively impacts readability and hence accessibility when background colors are applied to spans. See also the discussions minuted [here](https://www.w3.org/2016/02/18-tt-minutes.html#item05) and [here](https://www.w3.org/2016/02/25-tt-minutes.html#item05) and [this thread](https://lists.w3.org/Archives/Public/public-tt/2016Feb/0104.html). ## First question: is the height actually defined? [CSS 2 §10.6.1](https://www.w3.org/TR/CSS2/visudet.html#inline-non-replaced): > The height of the content area should be based on the font, but this specification does not specify how. A UA may, e.g., use the em-box or the maximum ascender and descender of the font. (The latter would ensure that glyphs with parts above or below the em-box still fall within the content area, but leads to differently sized boxes for different fonts; the former would ensure authors can control background styling relative to the 'line-height', but leads to glyphs painting outside their content area.) > >Note: level 3 of CSS will probably include a property to select which measure of the font is used for the content height. See also §10.6.6 and §10.6.7 in that specification. I'm still trying to work out what this means and whether it provides flexibility to implementers to make the inline box height be the same as the line height, or if there's some other calculation that applies. ## Second question: do we need syntax and semantics for clarifying it in TTML2? Pending the answer to the first question. Please view or discuss this issue at https://github.com/w3c/ttml2/issues/150 using your GitHub account
Received on Thursday, 3 March 2016 15:04:09 UTC