Chapter 26 Understanding Chart Optimization
The Draw Cycle and Chart Performance
Objective Chart, in its default mode, tries to display data in as complete a way as possible. Before every draw cycle, a scan is made of the data to determine the actual extent of the data range. This range is then used to calculate the correct values to be used on the axis labels. During the draw process, the axis labels modify themselves to fit the current data range. They also re-position themselves and check for and eliminate overlapping text. The final size of the rectangle enclosing the labels is then used to alter the size of the display rectangle before the data is finally drawn.
When the draw cycle is in progress, each data object optionally creates a feedback item so that data may be interrogated by using the mouse. These feedback items must be deleted before the beginning of the next draw cycle.
All of these processes take CPU time and can affect the performance of the chart system, especially if large amounts of data are to be drawn.