asticode / go-astisub / 34094376782

80%

Build Type

push

github

Committed by web-flow

Commit Message

Fix incorrect WebVTT size mapping for horizontal TTML text (#143)

* Fix incorrect WebVTT size mapping for horizontal TTML text

The bug was in propagateTTMLAttributes() where WebVTTSize was incorrectly
set to the height dimension (dimensions[1]) by default, when it should use
the width dimension (dimensions[0]) for horizontal text.

For TTML with default WritingMode "lrtb" (left-to-right, top-to-bottom),
the WebVTT size: property should represent the horizontal extent (width).
Only for vertical writing modes (starting with "tb") should it use height.

Changes:
- subtitles.go: Swapped the dimension assignments to use width by default
  and height only for vertical writing modes
- ttml_test.go: Updated test expectations to reflect correct behavior
  (WebVTTSize now correctly set to "100%" width instead of height values)

This ensures TTML extent="80% 15%" correctly maps to WebVTT size:80% for
horizontal text, not size:15%.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* Fix WebVTT REGION block format to match W3C specification

Changed from incorrect single-line format:
  Region: id=fred width=40% lines=3 regionanchor=0%,100%

To correct multi-line format:
  REGION
  id:fred
  width:40%
  lines:3
  regionanchor:0%,100%

According to W3C WebVTT specification, REGION blocks must use:
- Multi-line block format (not single-line)
- Colon separators (setting:value, not setting=value)
- Line breaks between each setting

The previous format was non-standard and may not be parsed correctly
by compliant WebVTT parsers.

Reference: https://www.w3.org/TR/webvtt1/#webvtt-region-settings

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* Fix TTML to WebVTT region mapping for bottom-aligned text

Changes:
1. RegionAnchor: Changed from "0%,0%" (top-left) to "0%,100%" (bottom-left)
2. ViewportAnchor: Calculate bottom edge position (origin Y + extent height)
   instead of using origin directly

Rationale:
According to W3C WebVTT spec, the defaul... (continued)

Coverage Stats

69 of 90 new or added lines in 2 files covered. (76.67%)

3 existing lines in 1 file now uncovered.

3202 of 4012 relevant lines covered (79.81%)

61.12 hits per line