- From: Glenn Adams <glenn@skynav.com>
- Date: Fri, 19 Feb 2016 11:23:23 -0700
- To: Nigel Megitt <nigel.megitt@bbc.co.uk>
- Cc: TTWG <public-tt@w3.org>
- Message-ID: <CACQ=j+cwhkpekUv8WpNsV+TOaf-WaJ+UCdgyS4LQDOFSbar-2w@mail.gmail.com>
On Fri, Feb 19, 2016 at 10:55 AM, Nigel Megitt <nigel.megitt@bbc.co.uk> wrote: > From: Glenn Adams <glenn@skynav.com> Date: Thursday, 18 February 2016 > 18:50 > > > > On Thu, Feb 18, 2016 at 9:05 AM, Nigel Megitt <nigel.megitt@bbc.co.uk> > wrote: > > > [snip] > > >> TTML2 >> >> nigel: Just to note that we have a merged PR, which I >> submitted, which updates all the issue links to point to >> github. >> ... The media timing semantics PR is still open. >> ... There's also been discussion of the use of inline block >> semantics. >> >> [15]https://github.com/w3c/ttml2/issues/146 >> >> [15] https://github.com/w3c/ttml2/issues/146 >> >> nigel: On this one I was concerned that the semantics lead to >> unwanted behaviours, but I think we can get around them >> ... mostly using nested span. The only outstanding issue I >> cannot find a way to solve right now is that BBC wants to be >> ... able to paint background areas behind spans that have the >> same height as lineHeight, and we cannot see a reliable >> ... way to do this. I plan to file an issue within the next >> week unless we can work out how. >> ... I can't see a way yet to achieve this in CSS, and it may >> need a new semantic on tts:padding to allow that to happen. >> >> It would be useful to see some images depicting desired results; this > looks similar to a problem I addressed in an SVG implementation (batik) to > add support for background coloring of text and tspan elements, wherein I > defined: > > > Something like the attached might help. The line height is in general > larger than the font size, and we wish to extend the background area of > each line area to match the line height so that adjacent line areas are > drawn without any gap in background. > > An effect similar to this is achieved on most browsers by using inline > display semantics but I have been unable to make this work alongside other > constraints such as text wrapping and white space pruning. > > I haven't found a way to do it in CSS, but it can be done reliably in > Javascript by querying the line areas heights and then updating padding. > Clearly we want a solution that is not dependent on scripting if possible, > though mapping a new non-CSS semantic may require it of course. > > > background-color: <color> > background-mode: bbox | lineHeight > background-padding: <length>{1,4} > > The second of these, background-mode, determined the extent of the > rectangles to colorize; > > > That seems exactly what we want. > > the third of these, background-padding, allows manually extending the > background color rectangle on any of the edges. > > We could do something like this in TTML2; however, it might not readily > translate to an HTML/CSS based renderer. > > > I'd like to explore how we can express this semantic in TTML2. Any > suggestions? > I would suggest we add the following style property attributes (names to be considered tentative at this point): tts:backgroundColorBounds: bbox | lineHeight (default: tts:backgroundColorOutdent: <length>{1,4} (default: 0px) We may need an additional value on the first that effectively means lineHeight + leading, depending on whether the definition of line height includes leading or not. [I think you want line height + leading (if line height does not already include leading), or just line height (if line height includes leading).] I use 'Outdent' suffix in the latter, as opposite of 'Indent'; 'Outset' is another option (opposite of 'Inset'); 'Padding' and 'Outline' are also options but may be confused with existing usage. Suggestions are welcome. > > [snip] > > Nigel > >
Received on Friday, 19 February 2016 18:24:12 UTC