It is now possible to reselect elements with scheduled transitions and redefine
associated tweens; this enables "post-selection" to customize the behavior of
reusable components undergoing transitions, such as an axis. This commit also
makes it much easier to sequence transitions.
Previously, a transition's tweens were stored privately by the transition and
could only be accessed through the transition. This made it impossible to modify
transitions created by components: the transition is not accessible externally,
and cannot be reselected from the document. Consider the following snippet:
g.select(".x.axis")
.call(xAxis)
.selectAll("text")
.attr("dy", null);
If `g` is a selection, then this code alters the appearance of the axis as
expected. However, if `g` is a transition, then transition.selectAll creates a
new concurrent transition, and now multiple tweens compete to set the "dy"
attribute. Oy!
Under the new design, an element's scheduled tweens are stored semi-privately on
the node (in the existing node.__transition__). Transition parameters can thus
be reselected and modified by transitions that share the same id. If you now
reselect a transitioning element, you modify the transition rather creating a
competing transition; this should be less surprising and allow greater control.
As a side-effect of this change, it is no longer possible to schedule concurrent
transitions on the same element, even with the same id: only one transition may
be active on a given element at any time. (Note that you can still schedule
multiple future transitions on the same element, and concurrent transitions on
different elements.) For example, you could previously schedule overlapping
transitions with different easing functions, delays or durations, provided you
were careful to avoid conflict. This seems like a relatively obscure use-case
compared to modifying a transition, so I believe this is a reasonable change.
This commit also changes transition.transition, such that the returned
transition starts at the end of the originating transition, rather than
overlapping. This makes it much easier to schedule sequenced transitions without
the complexity of transition.each("end") and d3.select(this).
Also, transitions are now simply arrays of nodes, consistent with selections!
Rather than producing separate files for each module, the default build now
produces a single file. This should encourage better page-load performance as
the files were relatively small. Also, it's easier to deal with only one file
rather than many, especially if you're not quite sure what the dependencies are.
You may still create minimized builds, if you don't want every feature.
This commit also demotes the chart components to the examples directory, rather
than keeping them as part of the core library. As always, D3 is not a charting
library, and these were ever only intended to serve as examples.
This caught a couple bugs in the previous commit. First, I wasn't sending the
correct index (i) to the "end" event listeners, because it was being masked by
a local variable. Second, the transition lock was being incorrectly deleted when
a transition is inherited on the same node and there is zero delay and
d3.timer.flush is called. There was potentially a related bug where the active
field was not being cleared on the transition lock. Yay tests!
Mike Bostock
Jason Davies