Propagating Changes to Point States

This is the more complicated part. There are several ways to make changes to point states that need to be propagated. You can use the mouse, certain menu items, or the :point-state message to change the state of one or more poins. (The :point-state message is a programatic way of accomplishing a state change that should be propagated to all linked plots. It is not a low-level mechanism for adjusting the internal states of points in individual plots.) When point states are changed in a plot p the state propagation process does the following:

Finds the list of plots linked to p with the :links message

For each point with index i changed in a single operation

For each linked plot q where the current point state of point i does not match the new state

(a)

Adjusts the internal state of point i in plot q and records the previous state. (The mechanism is undocumented. It happens to currently use knowledge of the implementation of the internal state when a graph is active. This is mostly for efficiency reasons that are no longer as important as they once were. It could now be done using an internal message, maybe called something like lisp-stat::adjust-internal-point-state. Insuring that linking is only applied to children of graph-proto that are active makes sure this will work -- the set of objects to which linking is applicable is part of the protocol.)

(b)

Sends q the :adjust-screen-point message with argument i. This allows plot q to redraw the point.

Sends each linked plot the :adjust-screen message.

talk about :needs-adjusting

There are two places at wich you can modify the linking process: at the individual point level

Do smoother example

rework steve's example?

redo alternate linking