LibWeb: Implement TimeRanges and HTMLMediaElement.seekable()

Author: https://github.com/Psychpsyo
Commit: aa243000f3
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3563
Reviewed-by: https://github.com/ADKaster ✅

Libraries/LibWeb/HTML/HTMLMediaElement.cpp

@@ -185,6 +185,18 @@ GC::Ref<TimeRanges> HTMLMediaElement::played() const
     return time_ranges;
 }
 
+// https://html.spec.whatwg.org/multipage/media.html#dom-media-seekable
+GC::Ref<TimeRanges> HTMLMediaElement::seekable() const
+{
+    auto& realm = this->realm();
+
+    // The seekable attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the
+    // user agent is able to seek to, at the time the attribute is evaluated.
+    auto time_ranges = realm.create<TimeRanges>(realm);
+    time_ranges->add_range(0, m_duration);
+    return time_ranges;
+}
+
 // https://html.spec.whatwg.org/multipage/media.html#dom-navigator-canplaytype
 Bindings::CanPlayTypeResult HTMLMediaElement::can_play_type(StringView type) const
 {
@@ -1566,11 +1578,46 @@ void HTMLMediaElement::seek_element(double playback_position, MediaSeekMode seek
     if (playback_position < 0)
         playback_position = 0;
 
-    // FIXME: 8. If the (possibly now changed) new playback position is not in one of the ranges given in the seekable attribute,
+    // 8. If the (possibly now changed) new playback position is not in one of the ranges given in the seekable attribute,
+    auto time_ranges = seekable();
+    if (!time_ranges->in_range(playback_position)) {
         // then let it be the position in one of the ranges given in the seekable attribute that is the nearest to the new
-    //           playback position. If two positions both satisfy that constraint (i.e. the new playback position is exactly in the
-    //           middle between two ranges in the seekable attribute) then use the position that is closest to the current playback
-    //           position. If there are no ranges given in the seekable attribute then set the seeking IDL attribute to false and return.
+        // playback position.
+
+        // If there are no ranges given in the seekable attribute then set the seeking IDL attribute to false and return.
+        if (time_ranges->length() == 0) {
+            set_seeking(false);
+            return;
+        }
+
+        double nearest_point;
+        Optional<double> other_nearest_point = {};
+        double distance = INFINITY;
+        for (size_t i = 0; i < time_ranges->length(); i++) {
+            for (double point : { MUST(time_ranges->start(i)), MUST(time_ranges->end(i)) }) {
+                auto point_distance = abs(playback_position - point);
+                if (point_distance < distance) {
+                    nearest_point = point;
+                    other_nearest_point = {};
+                    distance = point_distance;
+                } else if (point_distance == distance) {
+                    other_nearest_point = point;
+                }
+            }
+        }
+
+        // If two positions both satisfy that constraint (i.e. the new playback position is exactly in the middle between two ranges
+        // in the seekable attribute) then use the position that is closest to the current playback position.
+        if (other_nearest_point.has_value()) {
+            auto nearest_point_distance = abs(m_current_playback_position - nearest_point);
+            auto other_nearest_point_distance = abs(m_current_playback_position - other_nearest_point.value());
+            if (nearest_point_distance < other_nearest_point_distance) {
+                playback_position = nearest_point;
+            } else {
+                playback_position = other_nearest_point.value();
+            }
+        }
+    }
 
     // 9. If the approximate-for-speed flag is set, adjust the new playback position to a value that will allow for playback to resume
     //    promptly. If new playback position before this step is before current playback position, then the adjusted new playback position

Libraries/LibWeb/HTML/HTMLMediaElement.h

@@ -58,6 +58,7 @@ public:
 
     [[nodiscard]] GC::Ref<TimeRanges> buffered() const;
     [[nodiscard]] GC::Ref<TimeRanges> played() const;
+    [[nodiscard]] GC::Ref<TimeRanges> seekable() const;
 
     static inline constexpr auto supported_video_subtypes = Array {
         "webm"sv,

Libraries/LibWeb/HTML/HTMLMediaElement.idl

@@ -63,7 +63,7 @@ interface HTMLMediaElement : HTMLElement {
     attribute double playbackRate;
     [FIXME] attribute boolean preservesPitch;
     readonly attribute TimeRanges played;
-    [FIXME] readonly attribute TimeRanges seekable;
+    readonly attribute TimeRanges seekable;
     readonly attribute boolean ended;
     [Reflect, CEReactions] attribute boolean autoplay;
     [Reflect, CEReactions] attribute boolean loop;

Libraries/LibWeb/HTML/TimeRanges.cpp

@@ -27,24 +27,44 @@ void TimeRanges::initialize(JS::Realm& realm)
 // https://html.spec.whatwg.org/multipage/media.html#dom-timeranges-length
 size_t TimeRanges::length() const
 {
-    // FIXME: The length IDL attribute must return the number of ranges represented by the object.
-    return 0;
+    return m_ranges.size();
 }
 
 // https://html.spec.whatwg.org/multipage/media.html#dom-timeranges-start
-double TimeRanges::start(u32) const
+WebIDL::ExceptionOr<double> TimeRanges::start(u32 index) const
 {
-    // FIXME: The start(index) method must return the position of the start of the indexth range represented by the object,
+    // These methods must throw "IndexSizeError" DOMExceptions if called with an index argument greater than or equal to the number of ranges represented by the object.
+    if (index >= m_ranges.size())
+        return WebIDL::IndexSizeError::create(realm(), "Index argument is greater than or equal to the number of ranges represented by this TimeRanges object"_string);
+
+    // The start(index) method must return the position of the start of the indexth range represented by the object,
     // in seconds measured from the start of the timeline that the object covers.
-    return 0.0;
+    return m_ranges[index].start;
 }
 
 // https://html.spec.whatwg.org/multipage/media.html#dom-timeranges-end
-double TimeRanges::end(u32) const
+WebIDL::ExceptionOr<double> TimeRanges::end(u32 index) const
 {
-    // FIXME: The end(index) method must return the position of the end of the indexth range represented by the object,
+    // These methods must throw "IndexSizeError" DOMExceptions if called with an index argument greater than or equal to the number of ranges represented by the object.
+    if (index >= m_ranges.size())
+        return WebIDL::IndexSizeError::create(realm(), "Index argument is greater than or equal to the number of ranges represented by this TimeRanges object"_string);
+
+    // The end(index) method must return the position of the end of the indexth range represented by the object,
     // in seconds measured from the start of the timeline that the object covers.
-    return 0.0;
+    return m_ranges[index].end;
+}
+
+void TimeRanges::add_range(double start, double end)
+{
+    m_ranges.append({ start, end });
+}
+bool TimeRanges::in_range(double point)
+{
+    for (auto range : m_ranges) {
+        if (point >= range.start && point <= range.end)
+            return true;
+    }
+    return false;
 }
 
 }

Libraries/LibWeb/HTML/TimeRanges.h

@@ -8,22 +8,39 @@
 
 #include <LibJS/Forward.h>
 #include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
+// https://html.spec.whatwg.org/multipage/media.html#time-ranges
 class TimeRanges final : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(TimeRanges, Bindings::PlatformObject);
     GC_DECLARE_ALLOCATOR(TimeRanges);
 
 public:
+    // https://html.spec.whatwg.org/multipage/media.html#dom-timeranges-length
     size_t length() const;
-    double start(u32 index) const;
-    double end(u32 index) const;
+
+    // https://html.spec.whatwg.org/multipage/media.html#dom-timeranges-start
+    WebIDL::ExceptionOr<double> start(u32 index) const;
+
+    // https://html.spec.whatwg.org/multipage/media.html#dom-timeranges-end
+    WebIDL::ExceptionOr<double> end(u32 index) const;
+
+    void add_range(double start, double end);
+    bool in_range(double);
 
 private:
     explicit TimeRanges(JS::Realm&);
 
     virtual void initialize(JS::Realm&) override;
+
+    struct Range {
+        double start;
+        double end;
+    };
+
+    Vector<Range> m_ranges;
 };
 
 }