ngscopeclient saves a rolling buffer of previous waveforms in memory, allowing you to go back in time and see previous state of the system being debugged. Clicking on a timestamp in the history view (Fig. 9.1) pauses acquisition and loads the historical waveform data for analysis. History is captured regardless of whether the window is visible or not.
The history depth defaults to 10 waveforms, but can be set arbitrarily within the limits of available RAM. Older waveforms beyond the history limit are deleted as new waveforms are acquired. Any single waveform in history may also be deleted by right clicking on the line and selecting “delete" from the menu.
Interesting waveforms may be “pinned" in the history by checking the box in the “pin" column of the history view. Pinned waveforms are guaranteed to remain in the history buffer even when new waveforms arrive; only unpinned waveforms are eligible for automatic deletion to make space for incoming data.
If a waveform contains markers (8.5.2), it is automatically pinned and cannot be unpinned unless the marker (or entire waveform) is deleted. This prevents accidental loss of an important waveform: if the event was important enough to mark and name, it is probably worth keeping around.
Arbitrary text names may be assigned to a waveform by clicking the corresponding cell in the “label" column. Waveforms with a label are automatically pinned, since assigning a label implies the waveform is important.