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# 4.2 Tuning of the Timeline Window

Figure 4.3: Initial Timeline window with finer preview resolution.

One of the major improvements in the new Jumpshot and SLOG-2 is the scalability in terms of visualization performance. As shown in Figure 3.10, 14 bands of preview states cover the whole canvas in the initial Timeline window. By incrementing the parameter INIT_SLOG2_LEVEL_READ by 1 in the Preference window as in Table 3.16, the initial Timeline window is redisplayed, as shown in Figure 4.3. The new Timeline window has 27 bands of preview states instead of 14. The increased preview resolution offers a more detailed description of the logfile but at the expense of graphical performance because every increment of INIT_SLOG2_LEVEL_READ roughly doubles the number of drawables to be iterated during every zooming or scrolling.4.2 The biggest demand of graphical performance occurs when zooming to the level of only pure real drawables from the lower zoom level. The value of INIT_SLOG2_LEVEL_READ should be chosen so that Jumpshot does not appear to be too slow during the zooming to the pure real drawable level. For a fast graphics system, INIT_SLOG2_LEVEL_READ should be set higher than the default value 4 (e.g., 5) so that more information is present during each view. Slow graphics system should set INIT_SLOG2_LEVEL_READ lower (e.g., 3).

Another parameter that significantly affects the graphical performance is ARROW_ANTIALIASING in the Preference window. Setting the parameters to ON will force Jumpshot to draw all arrows including preview arrows with anti-aliasing lines. This proves to be an expensive graphical operation.4.3 Except when a high-quality picture is needed, for example during screen capture for a picture or when anti-aliasing lines are drawn with graphics hardware support, turning on ARROW_ANTIALIASING is not recommended.

#### Footnotes

...4.2
  It is true for a binary tree.
...4.3
  A typical timeline canvas with arrows will draw roughly a factor 3 slower with anti-aliasing on.

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