vbi_page::[struct].dirty Struct Reference

Data Fields
int	y0
int	y1
int	roll

Detailed Description

To speed up rendering these variables mark the rows which actually changed since the page has been last fetched from cache. y0 ... y1 are the first to last row changed, inclusive, in range 0 ... rows - 1. roll indicates the page has been vertically scrolled this number of rows, negative numbers up (towards lower row numbers), positive numbers down. For example -1 means row y0 + 1 ... y1 moved to y0 ... y1 - 1, erasing row y1 to all spaces.

Practically this is only used in Closed Caption roll-up mode, otherwise all rows are always marked dirty. Clients are free to ignore this information.