Xcode 3 Unleashed
Page 2

The Trace Document Window

The initial form of a trace document window is simple: a toolbar at the top, and a stack of instruments in the view that dominates the window. After you’ve recorded data into the document, the window becomes much richer. Let’s go through Figure 26.2 and identify the components.

The Toolbar

The toolbar comes in three sections. The controls at left (1) control recording and the execution of the target applications. There is a pause button for suspending and resuming data collection, a Record / Drive & Record / Stop button to start and stop data collection, and a loop button for running a recorded human-interface script repeatedly.

Note When you start recording, you will often be asked for an administrator’s password. The kind of deep monitoring many instruments do is, strictly speaking, a security breach, and the system makes you show you are authorized to do it.

Figure 26.2  A typical Instruments window, after data has been recorded. The Extended Detail pane (at right) has also been exposed. I discuss the numbered parts in the text.

The Default Target pop-up designates the process or executable that all instruments in the document will target, unless you specify different targets for individual instruments. The choices are as follows:

• All Processes. Data will be collected from all the processes, user and system, on the machine. For instance, the Core Data instruments can measure the Core Data activity of all processes. Not every instrument can span processes; if your document contains no instruments that can sample systemwide, this option is disabled.
• Attach to Process. Data will be collected from a process that is already running; select it from the submenu. Some instruments require that their targets be launched from Instruments, and cannot attach to running processes. If you use only nonattaching instruments, this option is disabled.
• Launch Executable. When you start recording, Instruments will launch the selected application or tool, and collect data from it. The submenu contains items for applications you’ve recorded previously, and has a Choose Executable item to select a fresh application.
• Instrument Specific. Each instrument will collect data from the target specified in the Target pop-up of its configuration inspector. The instruments in a trace document do not all have to collect data from the same target.

The center section (2) relates to time (see Figure 26.3). The clock view in the center of the toolbar displays the total time period recorded in the document. If you click the clock-face icon to the right of the time display, the clock shows the position of the “playback head” in the time scale at the top of the Track pane.

Figure 26.3  The center section of a trace document’s toolbar displays a clock, and controls for selecting a span of time within a recording. The clock displays the total time in the document (or, if you click the icon at the right of the clock, the position of the head”) and the run being displayed if there is more than one.

The clock view also controls which run of the document is being displayed. Each time you click Record, a new recording, with a timeline of its own, is added to the document. The run now being displayed is shown like “Run 1 of 2,” and you can switch among them by pressing the arrowhead buttons to either side.

Note You can also browse among runs by selecting View > Run Browser (ˆTab). The contents of the window will be replaced by a “Cover Flow” partial view of the traces in each run, along with particulars of when it was run, on what machine, and so on.

Most instruments will display subsets of the data they collect if you select a time span within the recording. To do so, move the playback head to the beginning of the span, and click the button on the left of the Inspection Range control; then move the head to the end of the span and click the button on the right. The selected span will be highlighted, and the Detail pane will be restricted to data collected in the span. To clear the selection, click the button in the middle.

Note Option-dragging across an interval in one of the traces will also set an inspection range.

The right section (3) provides convenient controls for display. Mini hides Instruments and displays a heads-up window for controlling recording from other applications. View pops up a menu that shows and hides the Detail and Extended Detail panes. Library shows and hides the Library window.

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