This is definitely the idea, and I have and success with a very similar architecture in previous projects. For the curious, here some notes about the ongoing work:
* simplified events dispatch, wrapping (hammer.js + jq_mousewheel)
- should get us some preliminary touch support as a bonus!
* allow multiple active "action" tools
- action tools have their own button on the toolbar
- one active per "type" of non-conflicting event: pan, tap, wheel, pinch, etc
- action tools include "selector" tools
- action tools optionally have a key that activates them
* allow unlimited active "inspector" tools
- inspectors active state toggle-able in a toolbar dropdown
- these respond only to mouse moves
* selectors and inspectors just report a geometry to a selection manager
* selection manager queries renderers for hit indices using geometry
- omitting some detail about a Selector class that manages multi-select, etc.
* selection manager reports/saves selection results on data sources
* anything can listen to/respond to these selection events
- tools
- annotations (including newly factored tooltip annotation)
- running user code, through a bokeh-server
After this plumbing is all in place, the major remaining parts to flesh it out are:
* add remaining hit tests for additional geometries to renderers
- "rect", "line", "poly" hit-testing
* add some new tools to report these geometries
- poly selection
- lasso tool
* add some new annotations that repond to inspections/selections
- improve hover to support creating multiple tooltips
- axis "position" tooltip that responds to mouse position
- whatever else people think of! 
The nice thing is all of the above can be done in a piecemeal fashion once the initial work is done.
Hope this is interesting/helps. If anyone is interested in pitching in with any of this, please don't hesitate to reach out!
Bryan
···
On Sep 28, 2014, at 5:36 PM, [email protected] wrote:
That sounds great!
I also agree with the philosophy on decoupling the roles of tools / renderers / selectors you mention on GitHub. A cleaner decoupling would likely allow for more functionality, without too much additional complexity for the user.
On Sunday, September 28, 2014 3:15:35 PM UTC-7, Bryan Van de ven wrote:
It seems lots of people are interested in this at once! I am actually working on a Pull Request for improved tools and selections now:
selection manager and tools/events refactor by bryevdv · Pull Request #1244 · bokeh/bokeh · GitHub
Hoping to merge this in a couple of days, and I will update the mailing list with more information (and a dev build to try out) after this work is merged to master.
Bryan
On Sep 28, 2014, at 5:11 PM, ronald....@gmail.com wrote:
> Setup:
>
>
> I have two-dimensional data I want to plot, similar to the 'scatter' example from the tutorial.
> The Bokeh tools such as the pan feature are useful, but I'd like to be able to add more functionality.
> For example, I want to be able to take 1D cuts (horizontal and vertical) of the data and plot the selected cut separately.
> What I have in mind is an additional tool, which would select the cut based on the last click in the window, or a similar feature.
> Is there a way for me to define custom tools, such as the one outlined here? If not, what approach would you suggest for such issues?
>
>
> Thanks!
>
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