Lines that start before the viewport, or start and end outside it, are missing

[ebelkina]

If a line starts earlier than the very first (left) bin of the view-port or starts and ends outside the view-port, it is not shown.

[vadimmidavvv]

Currently only lines that start withing the viewport are shown. This is not a critical issue for analysis of event logs seen so far. To draw required traces, the same additional information as for #4 required.