--- a/src/tree_cmd.cpp	Mon Sep 17 10:46:35 2007 +0000
+++ b/src/tree_cmd.cpp	Mon Sep 17 16:56:15 2007 +0000
@@ -21,12 +21,28 @@
 #include "variables.h"
 #include "genworld.h"
 
+/**
+ * List of tree placer algorithm.
+ *
+ * This enumeration defines all possible tree placer algorithm in the game.
+ */
 enum TreePlacer {
-	TP_NONE,
-	TP_ORIGINAL,
-	TP_IMPROVED,
+	TP_NONE,     ///< No tree placer algorithm
+	TP_ORIGINAL, ///< The original algorithm
+	TP_IMPROVED, ///< A 'improved' algorithm
 };
 
+/**
+ * Get a random TreeType for the given tile based on a given seed
+ *
+ * This function returns a random TreeType which can be placed on the given tile.
+ * The seed for randomness must be less or equal 256, use #GB on the value of Random()
+ * to get such a value.
+ *
+ * @param tile The tile to get a random TreeType from
+ * @param seed The seed for randomness, must be less or equal 256
+ * @return The random tree type
+ */
 static TreeType GetRandomTreeType(TileIndex tile, uint seed)
 {
 	switch (_opt.landscape) {
@@ -48,6 +64,15 @@
 	}
 }
 
+/**
+ * Make a random tree tile of the given tile
+ *
+ * Create a new tree-tile for the given tile. The second parameter is used for
+ * randomness like type and number of trees.
+ *
+ * @param tile The tile to make a tree-tile from
+ * @param r The randomness value from a Random() value
+ */
 static void PlaceTree(TileIndex tile, uint32 r)
 {
 	TreeType tree = GetRandomTreeType(tile, GB(r, 24, 8));
@@ -66,6 +91,15 @@
 	}
 }
 
+/**
+ * Place some amount of trees around a given tile.
+ *
+ * This function adds some trees around a given tile. As this function use
+ * the Random() call it depends on the random how many trees are actually placed
+ * around the given tile.
+ *
+ * @param tile The center of the trees to add
+ */
 static void DoPlaceMoreTrees(TileIndex tile)
 {
 	uint i;
@@ -87,6 +121,11 @@
 	}
 }
 
+/**
+ * Place more trees on the map.
+ *
+ * This function add more trees to the map.
+ */
 static void PlaceMoreTrees()
 {
 	uint i = ScaleByMapSize(GB(Random(), 0, 5) + 25);
@@ -97,7 +136,12 @@
 
 /**
  * Place a tree at the same height as an existing tree.
- *  This gives cool effects to the map.
+ *
+ * Add a new tree around the given tile which is at the same
+ * height or at some offset (2 units) of it.
+ *
+ * @param tile The base tile to add a new tree somewhere around
+ * @param height The height (like the one from the tile)
  */
 void PlaceTreeAtSameHeight(TileIndex tile, uint height)
 {
@@ -127,6 +171,11 @@
 	}
 }
 
+/**
+ * Place some trees randomly
+ *
+ * This function just place some trees randomly on the map.
+ */
 void PlaceTreesRandomly()
 {
 	uint i, j, ht;
@@ -183,6 +232,12 @@
 	}
 }
 
+/**
+ * Place new trees.
+ *
+ * This function takes care of the selected tree placer algorithm and
+ * place randomly the trees for a new game.
+ */
 void GenerateTrees()
 {
 	uint i, total;

--- a/src/tree_map.h	Mon Sep 17 10:46:35 2007 +0000
+++ b/src/tree_map.h	Mon Sep 17 16:56:15 2007 +0000
@@ -7,54 +7,123 @@
 
 #include "macros.h"
 
+/**
+ * List of tree types along all landscape types.
+ *
+ * This enumeration contains a list of the different tree types along
+ * all landscape types. The values for the enumerations may be used for
+ * offsets from the grfs files. These points to the start of
+ * the tree list for a landscape. See the TREE_COUNT_* enumerations
+ * for the amount of different trees for a specific landscape.
+ *
+ * @note TREE_INVALID may be 0xFF according to the coding style, not -1 (Progman)
+ */
 enum TreeType {
-	TREE_INVALID      = -1,
-	TREE_TEMPERATE    = 0,
-	TREE_SUB_ARCTIC   = 12,
-	TREE_RAINFOREST   = 20,
-	TREE_CACTUS       = 27,
-	TREE_SUB_TROPICAL = 28,
-	TREE_TOYLAND      = 32
+	TREE_INVALID      = -1,   ///< An invalid tree
+	TREE_TEMPERATE    = 0x00, ///< temperate tree
+	TREE_SUB_ARCTIC   = 0x0C, ///< tree on a sub_arctic landscape
+	TREE_RAINFOREST   = 0x14, ///< tree on the 'green part' on a sub-tropical map
+	TREE_CACTUS       = 0x1B, ///< a catus for the 'desert part' on a sub-tropical map
+	TREE_SUB_TROPICAL = 0x1C, ///< tree on a sub-tropical map, non-rainforest, non-desert
+	TREE_TOYLAND      = 0x20, ///< tree on a toyland map
 };
 
+/**
+ * Counts the number of treetypes for each landscape.
+ *
+ * This list contains the counts of different treetypes for each landscape. This list contains
+ * 5 entries instead of 4 (as there are only 4 landscape types) as the sub tropic landscape
+ * got two types of area, one for normal trees and one only for cacti.
+ */
 enum {
-	TREE_COUNT_TEMPERATE    = TREE_SUB_ARCTIC   - TREE_TEMPERATE,
-	TREE_COUNT_SUB_ARCTIC   = TREE_RAINFOREST   - TREE_SUB_ARCTIC,
-	TREE_COUNT_RAINFOREST   = TREE_CACTUS       - TREE_RAINFOREST,
-	TREE_COUNT_SUB_TROPICAL = TREE_SUB_TROPICAL - TREE_CACTUS,
-	TREE_COUNT_TOYLAND      = 9
+	TREE_COUNT_TEMPERATE    = TREE_SUB_ARCTIC   - TREE_TEMPERATE,  ///< number of treetypes on a temperate map
+	TREE_COUNT_SUB_ARCTIC   = TREE_RAINFOREST   - TREE_SUB_ARCTIC, ///< number of treetypes on a sub arctic map
+	TREE_COUNT_RAINFOREST   = TREE_CACTUS       - TREE_RAINFOREST, ///< number of treetypes for the 'green part' of a sub tropic map
+	TREE_COUNT_SUB_TROPICAL = TREE_SUB_TROPICAL - TREE_CACTUS,     ///< number of treetypes for the 'desert part' of a sub tropic map
+	TREE_COUNT_TOYLAND      = 9                                    ///< number of treetypes on a toyland map
 };
 
-/* ground type, m2 bits 4...5
- * valid densities (bits 6...7) in comments after the enum */
+/**
+ * Enumeration for ground types of tiles with trees.
+ *
+ * This enumeration defines the ground types for tiles with trees on it.
+ */
 enum TreeGround {
-	TREE_GROUND_GRASS       = 0, ///< 0
-	TREE_GROUND_ROUGH       = 1, ///< 0
-	TREE_GROUND_SNOW_DESERT = 2  ///< 0-3 for snow, 3 for desert
+	TREE_GROUND_GRASS       = 0, ///< normal grass
+	TREE_GROUND_ROUGH       = 1, ///< some rough tile
+	TREE_GROUND_SNOW_DESERT = 2  ///< a desert or snow tile, depend on landscape
 };
 
 
+/**
+ * Returns the treetype of a tile.
+ *
+ * This function returns the treetype of a given tile. As there are more
+ * possible treetypes for a tile in a game as the enumeration #TreeType defines
+ * this function may be return a value which isn't catch by an entry of the
+ * enumeration #TreeType. But there is no problem known about it.
+ *
+ * @param t The tile to get the treetype from
+ * @return The treetype of the given tile with trees
+ * @pre Tile t must be of type MP_TREES
+ */
 static inline TreeType GetTreeType(TileIndex t)
 {
 	assert(IsTileType(t, MP_TREES));
 	return (TreeType)_m[t].m3;
 }
 
-
+/**
+ * Returns the groundtype for tree tiles.
+ *
+ * This function returns the groundtype of a tile with trees.
+ *
+ * @param t The tile to get the groundtype from
+ * @return The groundtype of the tile
+ * @pre Tile must be of type MP_TREES
+ */
 static inline TreeGround GetTreeGround(TileIndex t)
 {
 	assert(IsTileType(t, MP_TREES));
 	return (TreeGround)GB(_m[t].m2, 4, 2);
 }
 
-
+/**
+ * Returns the 'density' of a tile with trees.
+ *
+ * This function returns the density of a tile which got trees. Note
+ * that this value doesn't count the number of trees on a tile, use
+ * #GetTreeCount instead. This function instead returns some kind of
+ * groundtype of the tile. As the map-array is finite in size and
+ * the informations about the trees must be saved somehow other
+ * informations about a tile must be saved somewhere encoded in the
+ * tile. So this function returns the density of a tile for sub arctic
+ * and sub tropical games. This means for sub arctic the type of snowline
+ * (0 to 3 for all 4 types of snowtiles) and for sub tropical the value
+ * 3 for a desert (and 0 for non-desert). The functionname is not read as
+ * "get the tree density of a tile" but "get the density of a tile which got trees".
+ *
+ * @param t The tile to get the 'density'
+ * @pre Tile must be of type MP_TREES
+ * @see GetTreeCount
+ */
 static inline uint GetTreeDensity(TileIndex t)
 {
 	assert(IsTileType(t, MP_TREES));
 	return GB(_m[t].m2, 6, 2);
 }
 
-
+/**
+ * Set the density and ground type of a tile with trees.
+ *
+ * This functions saves the ground type and the density which belongs to it
+ * for a given tile.
+ *
+ * @param t The tile to set the density and ground type
+ * @param g The ground type to save
+ * @param d The density to save with
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void SetTreeGroundDensity(TileIndex t, TreeGround g, uint d)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
@@ -62,64 +131,157 @@
 	SB(_m[t].m2, 6, 2, d);
 }
 
-
+/**
+ * Returns the number of trees on a tile.
+ *
+ * This function returns the number of trees of a tile (1-4).
+ * The tile must be contains at least one tree or be more specific: it must be
+ * of type MP_TREES.
+ *
+ * @param t The index to get the number of trees
+ * @return The number of trees (1-4)
+ * @pre Tile must be of type MP_TREES
+ */
 static inline uint GetTreeCount(TileIndex t)
 {
 	assert(IsTileType(t, MP_TREES));
 	return GB(_m[t].m5, 6, 2);
 }
 
+/**
+ * Add a amount to the tree-count value of a tile with trees.
+ *
+ * This function add a value to the tree-count value of a tile. This
+ * value may be negative to reduce the tree-counter. If the resulting
+ * value reach 0 it doesn't get converted to a "normal" tile.
+ *
+ * @param t The tile to change the tree amount
+ * @param c The value to add (or reduce) on the tree-count value
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void AddTreeCount(TileIndex t, int c)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
 	_m[t].m5 += c << 6;
 }
 
+/**
+ * Sets the tree amount of a tile.
+ *
+ * This function directly sets the amount of trees of a tile.
+ *
+ * @param t The tile to set the amount of trees
+ * @param c The number of trees
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void SetTreeCount(TileIndex t, uint c)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
 	SB(_m[t].m5, 6, 2, c);
 }
 
-
+/**
+ * Returns the tree growth status.
+ *
+ * This function returns the tree growth status of a tile with trees.
+ *
+ * @param t The tile to get the tree growth status
+ * @return The tree growth status
+ * @pre Tile must be of type MP_TREES
+ */
 static inline uint GetTreeGrowth(TileIndex t)
 {
 	assert(IsTileType(t, MP_TREES));
 	return GB(_m[t].m5, 0, 3);
 }
 
+/**
+ * Add a value to the tree growth status.
+ *
+ * This function adds a value to the tree grow status of a tile.
+ *
+ * @param t The tile to add the value on
+ * @param a The value to add on the tree growth status
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void AddTreeGrowth(TileIndex t, int a)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
 	_m[t].m5 += a;
 }
 
+/**
+ * Sets the tree growth status of a tile.
+ *
+ * This function sets the tree growth status of a tile directly with
+ * the given value.
+ *
+ * @param t The tile to change the tree growth status
+ * @param g The new value
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void SetTreeGrowth(TileIndex t, uint g)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
 	SB(_m[t].m5, 0, 3, g);
 }
 
-
+/**
+ * Get the tick counter of a tree tile.
+ *
+ * Returns the saved tick counter of a given tile.
+ *
+ * @param t The tile to get the counter value from
+ * @pre Tile must be of type MP_TREES
+ */
 static inline uint GetTreeCounter(TileIndex t)
 {
 	assert(IsTileType(t, MP_TREES));
 	return GB(_m[t].m2, 0, 4);
 }
 
+/**
+ * Add a value on the tick counter of a tree-tile
+ *
+ * This function adds a value on the tick counter of a tree-tile.
+ *
+ * @param t The tile to add the value on
+ * @param a The value to add on the tick counter
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void AddTreeCounter(TileIndex t, int a)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
 	_m[t].m2 += a;
 }
 
+/**
+ * Set the tick counter for a tree-tile
+ *
+ * This function sets directly the tick counter for a tree-tile.
+ *
+ * @param t The tile to set the tick counter
+ * @param c The new tick counter value
+ * @pre Tile must be of type MP_TREES
+ */
 static inline void SetTreeCounter(TileIndex t, uint c)
 {
 	assert(IsTileType(t, MP_TREES)); // XXX incomplete
 	SB(_m[t].m2, 0, 4, c);
 }
 
-
+/**
+ * Make a tree-tile.
+ *
+ * This functions change the tile to a tile with trees and all informations which belongs to it.
+ *
+ * @param t The tile to make a tree-tile from
+ * @param type The type of the tree
+ * @param set the number of trees
+ * @param growth the growth status
+ * @param ground the ground type
+ * @param density the density (not the number of trees)
+ */
 static inline void MakeTree(TileIndex t, TreeType type, uint count, uint growth, TreeGround ground, uint density)
 {
 	SetTileType(t, MP_TREES);