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rubidium

(svn r17776) -Codechange: [SDL] make "update the video card"-process asynchronious. Profiling with gprof etc. hasn't shown us that DrawSurfaceToScreen takes a significant amount of CPU; only using TIC/TOC it became apparant that it was a heavy CPU-cycle user or that it was waiting for something.
The benefit of making this function asynchronious ranges from 2%-25% (real time) during fast forward on dual core/hyperthreading-enabled CPUs; 8bpp improvements are, in my test cases, significantly smaller than 32bpp improvements.
On single core non-hyperthreading-enabled CPUs the extra locking/scheduling costs up to 1% extra realtime in fast forward. You can use -v sdl:no_threads to disable threading and undo this loss.
During normal non-fast-forwarded games the benefit/costs are negligable except when the gameloop takes more than about 90% of the time of a tick.
Note that allegro's performance does not improve with this system, likely due to their way of getting data to the video card. It is not implemented for the OS X/Windows video backends, unless (ofcourse) SDL is used there.
Funny is that the performance of the 32bpp(-anim) blitter is, at least in some test cases, significantly faster (more than 10%) than the 8bpp(-optimized) blitter when looking at real time in fast forward on a dual core CPU; it was slower.
The idea comes from a paper/report by Idar Borlaug and Knut Imar Hagen.

;
; Example file for the OpenTTD Base Graphics replacement sets.
; This file consists of basically two different parts:
;  * metadata
;  * information about the files
;
; Metadata contains information about the name, version and palette
; of the graphics set.
;
; == Getting started ==
; - you can't add comments after values
; - you have to fill the MD5 checksum for each file
; - you may not miss any of the metadata or files items
; - `openttd -h` lists all graphics replacements sets it found to be correct
; - `openttd -d grf=1` shows warnings/errors when parsing an .obg file
; - `openttd -I <name>` starts OpenTTD with the given set (case sensitive)
; - adding `graphicsset = <name>` to the misc section of openttd.cfg makes
;   OpenTTD start with that graphics set by default
; - there is a command line tool for all platforms called md5sum that can
;   create the MD5 checksum you need.
; - all files specified in this file are search relatively to the path where
;   this file is found, i.e. if the graphics files are in a subdir you have
;   to add that subdir to the names in this file to! It will NOT search for
;   a file named like specified in here.

[metadata]
; the name of the pack, preferably less than 16 characters
name         = example
; the short name (4 characters), used to identify this set
shortname    = XMPL
; the version of this graphics set (read as single integer)
version      = 0
; a fairly short description of the set
description  = foo
; palette used by the set; either DOS or Windows
palette      = DOS

; The files section lists the files that replace sprites.
; The file names are case sensitive.
[files]
; GRF file with the base sprites
base         = TRG1.GRF
; GRF file with logos, original terrain generator sprites
logos        = TRGI.GRF
; GRF file with extra arctic sprites
arctic       = TRGC.GRF
; GRF file with extra tropical sprites
tropical     = TRGH.GRF
; GRF file with extra toyland sprites
toyland      = TRGT.GRF
; NewGRF file using Actions 5, 7, 9 and A to replace sprites
; Must use a GRF ID starting with FF so it cannot be selected from
; the in-game NewGRF list and (thus) be loaded twice.
extra        = OPENTTDD.GRF

; The md5s section lists the MD5 checksum for the files that replace them.
; Note that the list of files is case sensitive. Each GRF listed in the
; files section must be listed here with it's MD5 checksum, otherwise you
; will get a lot of warnings when starting OpenTTD.
[md5s]
TRG1.GRF     = 9311676280e5b14077a8ee41c1b42192
TRGI.GRF     = da6a6c9dcc451eec88d79211437b76a8
TRGH.GRF     = ee6616fb0e6ef6b24892c58c93d86fc9
TRGC.GRF     = ed446637e034104c5559b32c18afe78d
TRGT.GRF     = fcde1d7e8a74197d72a62695884b909e
OPENTTDD.GRF = f829f62c137d6d7c6e272c481b796dd5

; The origin section provides the possibility to put and extra line into
; the warning that a file is missing/corrupt. This can be used to tell
; them where to find it. It works on the filename specified in the
; files section and if that is not found it will fall back to the default
; as shown below here.
[origin]
default      = You can find it on your Transport Tycoon Deluxe CD-ROM.
OPENTTDD.GRF = This file was part of your installation.