LibWeb: Implement VTTCue.line

Author: https://github.com/jamierocks
Commit: 8204143b08
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5840
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/WebVTT/VTTCue.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
+ * Copyright (c) 2024-2025, Jamie Mansfield <jmansfield@cadixdev.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -47,7 +47,8 @@ WebIDL::ExceptionOr<GC::Ref<VTTCue>> VTTCue::construct_impl(JS::Realm& realm, do
     // 9. Let cue’s WebVTT cue snap-to-lines flag be true.
     cue->m_snap_to_lines = true;
 
-    // FIXME: 10. Let cue’s WebVTT cue line be auto.
+    // 10. Let cue’s WebVTT cue line be auto.
+    cue->m_line = Bindings::AutoKeyword::Auto;
 
     // 11. Let cue’s WebVTT cue line alignment be start alignment.
     cue->m_line_alignment = Bindings::LineAlignSetting::Start;
@@ -114,6 +115,47 @@ void VTTCue::set_vertical(Bindings::DirectionSetting vertical)
     }
 }
 
+// https://w3c.github.io/webvtt/#cue-computed-line
+double VTTCue::computed_line()
+{
+    // 1. If the line is numeric, the WebVTT cue snap-to-lines flag of the WebVTT cue is false, and the line is negative
+    //    or greater than 100, then return 100 and abort these steps.
+    if (m_line.has<double>() && !m_snap_to_lines && (m_line.get<double>() < 0 || m_line.get<double>() > 100))
+        return 100;
+
+    // 2. If the line is numeric, return the value of the WebVTT cue line and abort these steps. (Either the WebVTT cue
+    //    snap-to-lines flag is true, so any value, not just those in the range 0..100, is valid, or the value is in the
+    //    range 0..100 and is thus valid regardless of the value of that flag.)
+    if (m_line.has<double>())
+        return m_line.get<double>();
+
+    // 3. If the WebVTT cue snap-to-lines flag of the WebVTT cue is false, return the value 100 and abort these steps.
+    //    (The line is the special value auto.)
+    if (!m_snap_to_lines)
+        return 100;
+
+    // FIXME: 4. Let cue be the WebVTT cue.
+
+    // FIXME: 5. If cue is not in a list of cues of a text track, or if that text track is not in the list of text tracks of
+    //    a media element, return −1 and abort these steps.
+
+    // FIXME: 6. Let track be the text track whose list of cues the cue is in.
+
+    // FIXME: 7. Let n be the number of text tracks whose text track mode is showing and that are in the media element’s list
+    //    of text tracks before track.
+    auto n = 0;
+
+    // 8. Increment n by one.
+    n++;
+
+    // 9. Negate n.
+    n = -n;
+
+    // 10. Return n.
+    dbgln("FIXME: Stubbed VTTCue.computed_line()");
+    return n;
+}
+
 // https://w3c.github.io/webvtt/#cue-computed-position-alignment
 Bindings::PositionAlignSetting VTTCue::computed_position_alignment()
 {

Libraries/LibWeb/WebVTT/VTTCue.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
+ * Copyright (c) 2024-2025, Jamie Mansfield <jmansfield@cadixdev.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -30,6 +30,8 @@ public:
         VerticalGrowingRight,
     };
 
+    using LineAndPositionSetting = Variant<double, Bindings::AutoKeyword>;
+
     static WebIDL::ExceptionOr<GC::Ref<VTTCue>> construct_impl(JS::Realm&, double start_time, double end_time, String const& text);
     virtual ~VTTCue() override = default;
 
@@ -42,6 +44,9 @@ public:
     bool snap_to_lines() const { return m_snap_to_lines; }
     void set_snap_to_lines(bool snap_to_lines) { m_snap_to_lines = snap_to_lines; }
 
+    LineAndPositionSetting line() const { return m_line; }
+    void set_line(LineAndPositionSetting line) { m_line = line; }
+
     Bindings::LineAlignSetting line_align() const { return m_line_alignment; }
     void set_line_align(Bindings::LineAlignSetting line_align) { m_line_alignment = line_align; }
 
@@ -58,6 +63,7 @@ public:
     void set_text(String const& text) { m_text = text; }
 
 protected:
+    double computed_line();
     Bindings::PositionAlignSetting computed_position_alignment();
 
 private:
@@ -75,6 +81,9 @@ private:
     // https://w3c.github.io/webvtt/#webvtt-cue-snap-to-lines-flag
     bool m_snap_to_lines { true };
 
+    // https://w3c.github.io/webvtt/#webvtt-cue-line
+    LineAndPositionSetting m_line { Bindings::AutoKeyword::Auto };
+
     // https://w3c.github.io/webvtt/#webvtt-cue-line-alignment
     Bindings::LineAlignSetting m_line_alignment { Bindings::LineAlignSetting::Start };
 

Libraries/LibWeb/WebVTT/VTTCue.idl

@@ -15,7 +15,7 @@ interface VTTCue : TextTrackCue {
     attribute VTTRegion? region;
     attribute DirectionSetting vertical;
     attribute boolean snapToLines;
-    [FIXME] attribute LineAndPositionSetting line;
+    attribute LineAndPositionSetting line;
     attribute LineAlignSetting lineAlign;
     [FIXME] attribute LineAndPositionSetting position;
     attribute PositionAlignSetting positionAlign;