+The @ref{progress-bar} is typically used to display the progress of a long running operation. It provides a visual clue that processing is underway. The @ref{progress-bar} can be used in two different modes: percentage mode and activity mode.
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+When an application can determine how much work needs to take place (e.g. read a fixed number of bytes from a file) and can monitor its progress, it can use the @ref{progress-bar} in percentage mode and the user sees a growing bar indicating the percentage of the work that has been completed. In this mode, the application is required to set @SlotRef{progress-bar,fraction} periodically to update the progress bar.
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+When an application has no accurate way of knowing the amount of work to do, it can use the @ref{progress-bar} in activity mode, which shows activity by a block moving back and forth within the progress area. In this mode, the application is required to call @ref{progress-bar-pulse} perodically to update the progress bar.
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+There is quite a bit of flexibility provided to control the appearance of the @ref{progress-bar}. Functions are provided to control the orientation of the bar, optional text can be displayed along with the bar, and the step size used in activity mode can be set.
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