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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.

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file heightmap.h Functions related to creating heightmaps from files. */

#ifndef HEIGHTMAP_H
#define HEIGHTMAP_H

/*
 * Order of these enums has to be the same as in lang/english.txt
 * Otherwise you will get inconsistent behaviour.
 */
enum {
	HM_COUNTER_CLOCKWISE, ///< Rotate the map counter clockwise 45 degrees
	HM_CLOCKWISE,         ///< Rotate the map clockwise 45 degrees
};

/**
 * Get the dimensions of a heightmap.
 * @param filename to query
 * @param x dimension x
 * @param y dimension y
 * @return Returns false if loading of the image failed.
 */
bool GetHeightmapDimensions(char *filename, uint *x, uint *y);

/**
 * Load a heightmap from file and change the map in his current dimensions
 *  to a landscape representing the heightmap.
 * It converts pixels to height. The brighter, the higher.
 * @param filename of the heighmap file to be imported
 */
void LoadHeightmap(char *filename);

/**
 * Make an empty world where all tiles are of height 'tile_height'.
 * @param tile_height of the desired new empty world
 */
void FlatEmptyWorld(byte tile_height);

/**
 * This function takes care of the fact that land in OpenTTD can never differ
 * more than 1 in height
 */
void FixSlopes();

#endif /* HEIGHTMAP_H */