New freight list sort mode: "by line"

[Nazalassa]

In large or complex networks, seeing how much goods want to take each line from a given station may help identifying problems faster. As such, I have written a patch which adds a sixth freight sort mode, "by line", that:

• For each good packet, looks up what lines it can take to reach its next interchange, or its destination;
• Groups good packets together according to this;
• Sorts the results by amount.

The main advantage over "via (amount)" is that there may be much less entries in the freight list, and we directly get the line's load at the station.

Here is the result at a (rather overcrowded) station:

[danivenk]

Good work! I have been wanting to make something similar.

There is only one problem with that sorting mode tho.
You differentiate between 2 lines that go between the same two halts by combining them with "or" between the linenames.
However what if the line names are really long? Or you have many more lines that go the same 2 halts.
I have on some of my maps halts that are connected with at least 5 or 6 lines. In it's current form I can see that become quite cluttered.

So maybe a better way is to add a list of lines / lineless convoys when sort by line is selected and it shows only the passengers that would go via that line. Or maybe even have the line selector always there so you can within a line filtered list sort by via etc.