Session Time Control

Session Time Control offers the ability to view and control Session time in a variety of ways. This page describes how this feature works and the control and display options available to you.


Fig. 1 - A Typical Time Control Window

Under normal circumstances, displays respond to changes in real time as a Session runs. Time Control gives you the ability to both change the Session's current time, and to speed it up or slow it down, both for Sessions active real time and archived Sessions. It allows you to run time in reverse with the same ability to speed up or slow time down. Figure 1 shows a typical window.

Time Control windows support multiple Session panels with a single control panel. The controls operate on the selected Session, and let you move to the oldest or newest date, run forwards or backwards, and stop. The time mode icon button lets you switch between real time (clock icon) and relative time (stop watch icon). The round button on the right hand side lets you attach (green) or detach (red) from a session.

The per-Session panels display the oldest and newest date, the current date, and an animating indicator when the session is running. Current time can be shown as Calendar (GMT) or Epoch (relative) time based on some date you define. The bottom slider allows you to change the current time when the Session is stopped; in addition, you can actually set a precise time by selecting and keying in each current time numeric field.

Controls at the window bottom let you open a drawer with Speed and Update controls, open the Preferences Sheet, and select a particular Run. It also displays the current speed.


Fig. 2 - Preferences

Click on the i button to access the various preferences (Figure 2). The Current Time display can be optioned for a wide range of maximum and minimum time increments, individually for calendar and epoch time. For example, in Calendar mode you might want to just see Hours, Minutes, and Seconds - but in Epoch mode Minutes, Seconds, and Milliseconds.

You can option the speed control to show one of three types of exponential display. Engineering constrains the exponent to a power of three, and SI (International System of Units) uses single character suffixes (G=e9, M=e6, k=e3, m=e-3, u=e-6, n=e-9). Note that you can key values in using any of these formats.

The Precision slider sets both the displayed precision and the actual numeric factor used to evaluate Current Time. Thus, you could set a precision of 1 and get actual increments of 1, 2, 3, 4, ..., 11, 12, 13....

The Facilitated Time Entry feature enables expedited keying. Normally, to set a particular Current Time value, you would double click on the particular time field, key in a number, then tab (forwards) or shift-tab (backwards) to change the next field. When set, this feature determines when sufficient numbers have been entered, and automatically moves key focus to the next time field (if the shift key is down focus moves backwards).

Controlling Session Time

Fig. 3 - Unattached Session in Real Time Mode

Each Interface can have a Time Control window associated with it displaying one or more Sessions. When no Sessions have been created, the display will show NO SOURCE SESSION. Once one is created, the display will switch to NO RUNS until the session is started or unarchived.

When the sessions starts, the display will looks something like Figure 3. The session name is shown in the upper left, the Current Time is shown in the center, and the oldest and newest times are shown on the bottom corners. The round right button uses three colors (with differing brightness) to reflect the current attached state: White -> no connection possible, Red (dark) -> disconnected, and Green (light) -> attached. When the button is Red or Green, pressing it switches to the other state. Until you attach to a Session, all time controls are disabled.

To attach to a Session, press the Red button: time is set to the newest possible time, the Forward button is activated, and the round button turns Green. At this point, essentially nothing has changed vis a vie Session time—the Interface updates as it was in real time.

Press the Stop button and time stops updating. Now, you can set the time either by dragging the slider (whose thumb just turned blue) or edit any of the Current Time values. In addition, you can click on the Move to Oldest Time button or the Move to Newest Time button. Pressing the Reverse button runs time in reverse.

Epoch Time

Fig. 4 - Epoch Time Mode

Epoch Time lets you set an arbitrary reference time (within the Session's time range), and then the Current Time display shows the difference between this reference and the current real time.

This value is set when the following conditions occur: the Session is attached, the play control is set to Stop, and you click on the Clock Icon to switch to the Epoch Time. The actual Epoch time is shown at the top of the display.

As long as the Session is playing (forward or reverse), you can switch back and forth between Epoch Time and Calendar Time without changing the Epoch reference time.

Speed Control and Update Rate

Fig. 5 - Speed and Update Controls

Click the triangle control to expose or hide the drawer containing two additional controls (see Figure 5). The Update control lets you set the number of display updates per second sent to the Interface.

Since visual updates consume computer processing resources, higher numbers increase system stress. Apple provides the Activity Monitor app that you can use to monitor processor load of any app or the overall system, so you can get real data if you believe this value is not optimal.

The Speed Control dial allows you to vary the rate at which time updates, exactly as a DVD/VCR speed control works. The primary difference is that this control uses a logarithmic scale that ranges from 1.0e-9 to 1.0e+9. Recall the precision—the number of valid digits—can be set in the Settings sheet.

You can change the speed while the Session is playing, as well as the number of updates.

Controlling Multiple Sessions

You can manipulate multiple Sessions with Time Control. When there are multiple Sessions, the slider on the far right of the window activates. Sessions appear alphabetically sorted in a scrollable stack, so you can move the slider so that only the Session of interest shows. Alternately, you can resize the window to show more than one Session.

The controls within the silver colored box and the Speed control act on the currently selected Session. To select a particular Session, click on its name or anywhere in its display. Once a Session has been configured, and its play state and speed set, you can switch to another Session and let the previous one run.