From 73a05f9163a9494057d4a1a6840657ed3f54bc68 Mon Sep 17 00:00:00 2001
From: Jamie Mansfield <jmansfield@cadixdev.org>
Date: Wed, 13 Aug 2025 13:51:00 +0100
Subject: [PATCH] LibWeb: Implement VTTCue.position

---
 Libraries/LibWeb/WebVTT/VTTCue.cpp | 23 ++++++++++++++++++++++-
 Libraries/LibWeb/WebVTT/VTTCue.h   |  7 +++++++
 Libraries/LibWeb/WebVTT/VTTCue.idl |  2 +-
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibWeb/WebVTT/VTTCue.cpp b/Libraries/LibWeb/WebVTT/VTTCue.cpp
index c012626ab74..270949f2ee8 100644
--- a/Libraries/LibWeb/WebVTT/VTTCue.cpp
+++ b/Libraries/LibWeb/WebVTT/VTTCue.cpp
@@ -53,7 +53,8 @@ WebIDL::ExceptionOr<GC::Ref<VTTCue>> VTTCue::construct_impl(JS::Realm& realm, do
     // 11. Let cue’s WebVTT cue line alignment be start alignment.
     cue->m_line_alignment = Bindings::LineAlignSetting::Start;
 
-    // FIXME: 12. Let cue’s WebVTT cue position be auto.
+    // 12. Let cue’s WebVTT cue position be auto.
+    cue->m_position = Bindings::AutoKeyword::Auto;
 
     // 13. Let cue’s WebVTT cue position alignment be auto.
     cue->m_position_alignment = Bindings::PositionAlignSetting::Auto;
@@ -156,6 +157,26 @@ double VTTCue::computed_line()
     return n;
 }
 
+// https://w3c.github.io/webvtt/#cue-computed-position
+double VTTCue::computed_position()
+{
+    // 1. If the position is numeric between 0 and 100, then return the value of the position and abort these steps.
+    //    (Otherwise, the position is the special value auto.)
+    if (m_position.has<double>() && m_position.get<double>() >= 0 && m_position.get<double>() <= 100)
+        return m_position.get<double>();
+
+    // 2. If the cue text alignment is left, return 0 and abort these steps.
+    if (m_text_alignment == Bindings::AlignSetting::Left)
+        return 0;
+
+    // 3. If the cue text alignment is right, return 100 and abort these steps.
+    if (m_text_alignment == Bindings::AlignSetting::Right)
+        return 100;
+
+    // 4. Otherwise, return 50 and abort these steps.
+    return 50;
+}
+
 // https://w3c.github.io/webvtt/#cue-computed-position-alignment
 Bindings::PositionAlignSetting VTTCue::computed_position_alignment()
 {
diff --git a/Libraries/LibWeb/WebVTT/VTTCue.h b/Libraries/LibWeb/WebVTT/VTTCue.h
index 276a0734ca0..2bd2ec4840e 100644
--- a/Libraries/LibWeb/WebVTT/VTTCue.h
+++ b/Libraries/LibWeb/WebVTT/VTTCue.h
@@ -50,6 +50,9 @@ public:
     Bindings::LineAlignSetting line_align() const { return m_line_alignment; }
     void set_line_align(Bindings::LineAlignSetting line_align) { m_line_alignment = line_align; }
 
+    LineAndPositionSetting position() const { return m_position; }
+    void set_position(LineAndPositionSetting position) { m_position = position; }
+
     Bindings::PositionAlignSetting position_align() const { return m_position_alignment; }
     void set_position_align(Bindings::PositionAlignSetting position_align) { m_position_alignment = position_align; }
 
@@ -64,6 +67,7 @@ public:
 
 protected:
     double computed_line();
+    double computed_position();
     Bindings::PositionAlignSetting computed_position_alignment();
 
 private:
@@ -87,6 +91,9 @@ private:
     // https://w3c.github.io/webvtt/#webvtt-cue-line-alignment
     Bindings::LineAlignSetting m_line_alignment { Bindings::LineAlignSetting::Start };
 
+    // https://w3c.github.io/webvtt/#webvtt-cue-position
+    LineAndPositionSetting m_position { Bindings::AutoKeyword::Auto };
+
     // https://w3c.github.io/webvtt/#webvtt-cue-position-alignment
     Bindings::PositionAlignSetting m_position_alignment { Bindings::PositionAlignSetting::Auto };
 
diff --git a/Libraries/LibWeb/WebVTT/VTTCue.idl b/Libraries/LibWeb/WebVTT/VTTCue.idl
index 31f5a39e8a5..4f57b335ce7 100644
--- a/Libraries/LibWeb/WebVTT/VTTCue.idl
+++ b/Libraries/LibWeb/WebVTT/VTTCue.idl
@@ -17,7 +17,7 @@ interface VTTCue : TextTrackCue {
     attribute boolean snapToLines;
     attribute LineAndPositionSetting line;
     attribute LineAlignSetting lineAlign;
-    [FIXME] attribute LineAndPositionSetting position;
+    attribute LineAndPositionSetting position;
     attribute PositionAlignSetting positionAlign;
     attribute double size;
     attribute AlignSetting align;