RE: beforescroll as the "intention" contract for scrolling

Hi Rick! It sounds like you would be a great asset to have for our Intentions conversations! The purpose of the Intentions Explainer is to bring together known and future Intention-style events so that developers have a consistent experience. Extensibility is very much a goal (maybe I should make that clearer in the doc), and composition is something that has crossed my mind but I don’t currently have a firm handle on. It would be very valuable to have your contribution on the subject. Further, scrolling is not something that we currently have an expert for, so having help there would also be great.

We have just added a meeting to discuss these subjects at TPAC on Monday between 15-16:00. Are you (or someone else on your team) going to be there so you can join our conversation?

I have been working with Julie Parent on the editing side at Google, and I understand that Kenji Baheux just took over the area from her. If you have more contacts that might be interested at Google (browsers, sites, frameworks), that would be great too- send them over to join our list!

From: rbyers@google.com [mailto:rbyers@google.com] On Behalf Of Rick Byers
Sent: Tuesday, September 23, 2014 2:00 PM
To: public-editing-tf@w3.org
Cc: Timothy Dresser
Subject: beforescroll as the "intention" contract for scrolling

Hi,
I just read your explainer<http://w3c.github.io/editing-explainer/commands-explainer.html>, and although I don't have much context on editing in particular, the high level concepts really resonated with me.  We (blink input team) have been struggling with related problems around input for awhile and now have a proposal<https://docs.google.com/a/chromium.org/document/d/1oEVWIVdMZ2OlVZMvcZZ3IgaT6RAUNSKAzpzb9AlVeLw/edit#heading=h.kd0gtwwz5bf9> which we're pretty excited about.

Our 'beforescroll' event corresponds exactly to your definition of an 'intention' for scrolling.  However our motivation is pretty different from what you describe as: "... several issues including difficultly understanding what a user intends, complexity in building Accessible sites, and complex localization".  These are probably problems for scrolling too, but the bigger problems in our mind are around composition and extensibility.  Without a contract for the intention, components that transform behavior into actions can't compose properly with each other.  In the context of scrolling, this means it's impossible for JavaScript to customize scrolling because they'd have to re-implement everything themselves and there's no API exposed for some browser behavior so no way to compose with it. By defining a contract for mediating composition (the event that defines the intention), we enable customization of actions (custom generators of the event) and customization of behavior (custom consumers of the event) independently in a way that composes properly with other actions and behaviors for the same intention.  We see this as an important step towards a more extensible web<http://extensiblewebmanifesto.org> (cleanly dividing the platform into a kernel of core primitives and a framework layer of optional components built on top of those primitives).  If the abstraction also enables better accessibility, understandability and localization too then that's great too.

Although it's not really my area of expertise, I think we also have composition/extensibility problems with text editing in blink as well.  Eg. how is a rich custom editor like Google Docs (which manages text layout and selection itself in JS) supposed to properly integrate with the text editing facilities of a touch-centric browser?  What if you want to build an editor which does all it's rendering using canvas or WebGL instead of DOM?  As you work on the appropriate "intention" APIs for text editing, I'd urge you to consider how it can make the platform more easily extensible - breaking down what today are monolithic "magic" browser features into components that can be used or replaced individually according to the needs of the app.  If this is a direction you're interested in and would like involvement from the blink team, I can try to find the right people to get involved - this is directly relevant to blink's high-level mission of making the web more competitive with native mobile platforms.

Thoughts?
  Rick