[webvtt] position, text_alignment issue

k2nagaraju has just created a new issue for https://github.com/w3c/webvtt:

== position, text_alignment issue ==
According  to spec "https://w3c.github.io/webvtt/"

problem 1:
=======
if cue contains "position:0% align:start"
https://w3c.github.io/webvtt/#webvtt-cue-position =>computed position is 0, 
https://w3c.github.io/webvtt/#webvtt-cue-position-alignment =>computed position alignment is center

https://w3c.github.io/webvtt/#processing-model
If the computed position alignment is center, and the computed position is less than or equal to 50
maximum_size = computed position * 2; which is 0

cue_size is minimum of (cue_size or maxium_size). From this cue_size is 0.
In spec it is not specified what should be done if cue_size is zero.

Problem 2:
=======
if cue contains "position:10% align:start"
https://w3c.github.io/webvtt/#webvtt-cue-position =>computed position is 10, 
https://w3c.github.io/webvtt/#webvtt-cue-position-alignment =>computed position alignment is center

https://w3c.github.io/webvtt/#processing-model
If the computed position alignment is center, and the computed position is less than or equal to 50
maximum_size = computed position * 2; which is 20

cue_size is minimum of (cue_size or maxium_size). From this cue_size is 20.
Determine the value of x-position for horizontal writing direction
If the computed position alignment is center alignment
Let x-position be the computed position minus half of size. => 10-20/2 =0;

Here position whichever specified in cue is not considered.
Same problem is there for
position> 50 && align:end;
position< 50 && align:start; cases 


Please view or discuss this issue at https://github.com/w3c/webvtt/issues/413 using your GitHub account

Received on Tuesday, 14 November 2017 13:33:31 UTC