Canvas bindings are triggered by a mouse/keyboard gesture over the plot as a whole.
l_bind_item(widget, tags, event, callback)
widget path as a string or as an object handle
item tags as as explained in
event patterns as defined for Tk canvas widget http://www.tcl.tk/man/tcl8.6/TkCmd/bind.htm#M5.
callback function is an R function which is called by the Tcl interpreter if the event of interest happens. Note that in loon the callback functions support different optional arguments depending on the binding type, read the details for more information
item binding id
Item bindings are used for evaluating callbacks at certain mouse and/or keyboard gestures events (i.e. X events) on visual items on the canvas. Items on the canvas can have tags and item bindings are specified to be evaluated at certain X events for items with specific tags.
Note that item bindings get currently evaluated in the order that they are added.
Bindings, callbacks, and binding substitutions are described in detail in
loon's documentation webpage, i.e. run