= 5-Year Plan: A Retrospective
''by Simon Fraser''

'''5 years ago, in a meeting room not so far away…'''

- DOM Event Loop
    - Started working on it.
    - Now called the Event Loop
    - Benefits and problems are still accurate
- Render Tree Refcounting
    - Not done this
    - Haven’t found a real need to do this yet
- Painting: Display Lists
    - Have done experiments
    - Testing with MotionMark is a performance regression
    - Lost parallelism
    - Didn’t turn it on, may come back and revisit it
- Image Decoding
    -  Knew we had problems with this on main thread
    - Decoding sync on main thread
    - Can’t do it by default because of flashy painting
    - Added decoding=async on img element to turn it on
    - Or call API to ask for decoding on image and get a Promise
    - Async decoding on first load
    - This is done and we’re pretty happy with it
- Layout State Machine
    - Making it harder to make mistakes interacting with RenderTree
    - Be on a call stack iterating on layer list for hit testing
    - Detect when mistakes happen and trigger assertions
    - Fixed a bunch of issues of mutating trees in the middle of…
    - Big benefit of event loop is: move all code that fires events to updateRendering steps and other well defined places
    - Made good progress
- Compositing
    - Downstream was making compositing decisions by looking at whole list of drawing commands
        - Haven’t done it
        - Earlier this year I did compositing updates are incremental with dirty bits
- Hackability
    - RenderRegions were removed which was good
    - Working on inline layout
        - Goals to simplify inline layout code
    - ScrollableArea and FrameVIew
        - Nothing really changed
        - State of FrameLoader et. al… still not great
    - Relationships between Document Frame, Dom Window and page are still pretty confusing
    - Selection still has specialized versions
- Threading
    - Can we do more in threads?

'''4 years ago, in the same meeting room not so far away…'''

- Optimizing layout
- IndexedDB optimizations
- Cleaning up loading code
- Page cache clean up
    - We’re doing it!
- CSS properties status JSON and on webkit.org
- Event Loop
    - Same stuff, making progress
- Fetch API
    - Done
- Service Worker
    - Done
- Intersection Observer
    - Done
- Scroll-linked Effects
    - Some work, but no really progress
- Houdini proposal
    - Prototype of custom paint, but no where accessible
- Page & Friends
    - Too many scrolling architectures
    - iOS WK1 is different, iOS WK2 uses UI side compositing
- Code Organization
    - PAL library
        - Some of its there
- Layout & Rendering
    - Fundamentally hasn’t changed
    - LFC work is still underway, beyond experimental
        - Rewrite of the layout code
        - Making good progress
        - Block layout 80-90% done
        - Now doing table layout
    - Inine layout work too
- Remove widgets
    - Still have them
    - Need to get rid of it
- Continuations
    - Nothing happened
- Compositing
    - Still do compositing updates on every forced layout
    - Ideally only once every rendering step
        - Hoping to do it this year
- Debuggability
    - Log Channels: new log channels
    - Use TextStream to make things log-able
    - I want to log a RenderStyle and only the properties different from the default
        - And show diff
    - Still have progress to be made
- Next Year
    - Figure out where logging goes