This is useful to provide a feature-agnostic, stable random value that differs between games.
One of the possible uses is to e.g. use it to create pseudo-random regions for towns or industries.
It now follows very simple rules:
0 - Fatal, user should know about this
1 - Error, but we are recovering
2 - Warning, wrong but okay if you don't know
3 - Info, information you might care about
4 -
5 - Debug #1 - High level debug messages
6 - Debug #2 - Low level debug messages
7 - Trace information
This opens up the true power of the TGP terrain generator, as it
is no longer constrainted by an arbitrary low map height limit,
especially for extreme terrain types.
In other words: on a 1kx1k map with "Alpinist" terrain type, the
map is now really hilly with default settings.
People can still manually limit the map height if they so wish,
and after the terrain generation the limit is stored in the
savegame as if the user set it.
Cheats still allow you to change this value.
Setting the snow coverage (in % of the map) makes a lot more sense
to the human, while still allowing the niche player to set (by
finding the correct %) a snow line height they like. This makes for
easier defaults, as it decoupled terrain height from amount of snow.
Maps can never be 100% snow, as we do not have sprites for coastal
tiles.
Internally, this calculates the best snow line height to approach
this coverage as close as possible.
Basically, modal windows had their own thread-locking for what
drawing was possible. This is a bit nonsense now we have a
game-thread. And it makes much more sense to do things like
NewGRFScan and GenerateWorld in the game-thread, and not in a
thread next to the game-thread.
This commit changes that: it removes the threads for NewGRFScan
and GenerateWorld, and just runs the code in the game-thread.
On regular intervals it allows the draw-thread to do a tick,
which gives a much smoother look and feel.
It does slow down NewGRFScan and GenerateWorld ever so slightly
as it spends more time on drawing. But the slowdown is not
measureable on my machines (with 700+ NewGRFs / 4kx4k map and
a Debug build).
Running without a game-thread means NewGRFScan and GenerateWorld
are now blocking.
A conforming compiler with a valid <mutex>-header is expected.
Most parts of the code assume that locking a mutex will never fail unexpectedly,
which is generally true on all common platforms that don't just pretend to
be C++11. The use of condition variables in driver code is checked.
Peter Nelson