Forces bar content to be updated. By default bar content is periodically refreshed when TwDraw is called (the update frequency is defined by the bar parameter refresh). This function may be called to force a bar to be immediately refreshed at next TwDraw call.

Bar identifier.

• 1 if the succeeded.
• 0 if an error occurred (call TwGetLastError to retrieve the error).

TwDraw, TwNewBar