Bug 287433 – Clicking on Safari video timeline UI does not always seek to time requested

• Component: Media
• Status: NEW

[Rob Smith]

Created attachment 474187 [details]
Event log showing that the current video time changes to 1 second earlier in UI (step 4)

# Description

Clicking on Safari video timeline UI does not always seek to time requested

# Steps to reproduce

1. Load the video in the web page attached to see the event log.
2. Press the Safari play control to play the video to the end (only 5 secs long).
3. Click on the '<' button to seek to 1 second earlier.
4. Note that the current video time changes to 1 second earlier in UI and event log - see example screenshot Seek_earlier_javascript_250102.png.
5. Click on the Safari timeline to seek to an earlier non-zero time.
6. Note that the current video time changes to zero in UI and event log - see example screenshot Seek_earlier_safari_ui_250102.png.

# Expected result

Clicking on the video timeline UI should always seek to the time requested and behave consistently with the HTMLMediaElement.currentTime Javascript interface - see custom buttons on web page attached.

The expected result is observed when the test is performed using either Firefox 128.5.2esr(64-bit) or Chrome 131.0.6778.140.

# Actual result

Clicking on the video timeline UI to request an earlier time can seek to time zero in Safari 18.2(20620.1.16.11.8) and is inconsistent with the Javascript interface.

# Further details

This issue may be related to issue 287430: "Playing video in Safari can generate non-monotonic 'timeupdate' events". This behaviour is not unique to the example video file provided.

[Rob Smith]

Created attachment 474188 [details]
Event log showing that the current video time changes to zero in UI (step 6)

[Rob Smith]

Created attachment 474189 [details]
Sample web page used to demonstrate bug and generate screenshot

[Radar WebKit Bug Importer]

<rdar://problem/145005632>