isPageRequestedFor method
Checks if the page for the given messageIndex is already requested.
Note that the messageIndex is expected to be based on
full messageSequence, where index 0 is newest message and
size-1 is the oldest message.
Implementation
bool isPageRequestedFor(int messageIndex) {
final index = length - messageIndex - 1;
return index >
length - (pagedSequence.currentPageIndex * pagedSequence.pageSize);
}