Tracing is like executing, only it’s slower — slow enough that you can actually see the blue arrow moving along the path of execution. To trace:

• Choose Script > Trace (or Option-click the Execute / Resume button in the toolbar).

While tracing, a speed slider appears below the title bar and toolbar of the script window. You can adjust the tracing speed (from “tortoise” at the left to “hare” at the right) while tracing is going on.

Tracing is in one sense just a slower form of execution, and will pause for the same reasons (e.g., because a breakpoint is encountered, or because you issue the Pause command). However, what’s really happening is that Script Debugger is pausing and resuming after every executed line. This means that you can see more than the blue arrow moving — you can also see the call stack growing and shrinking, and the variable values changing, just as you would if you if were repeatedly issuing the Step Into command.

Trace has the same options for executing handlers as Execute.