(svn r11263) -Codechange: Reduce code duplication between DrawBridgePillars and HasFoundation{NW|NE}. Patch by frosch.

3 files changed, 91 insertions, 44 deletions

diff --git a/src/landscape.cpp b/src/landscape.cpp
index 0e61d5010..be845161a 100644
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -206,6 +206,32 @@ uint GetSlopeZ(int x, int y)
 	return _tile_type_procs[GetTileType(tile)]->get_slope_z_proc(tile, x, y);
 }
 
+/**
+ * Determine the Z height of the corners of a specific tile edge
+ *
+ * @pre z1 and z2 must be initialized (typ. with TileZ). The corner heights just get added.
+ *
+ * @param tileh The slope of the tile.
+ * @param edge The edge of interest.
+ * @param z1 Gets incremented by the height of the first corner of the edge. (near corner wrt. the camera)
+ * @param z2 Gets incremented by the height of the second corner of the edge. (far corner wrt. the camera)
+ */
+void GetSlopeZOnEdge(Slope tileh, DiagDirection edge, int *z1, int *z2)
+{
+	static const Slope corners[4][4] = {
+		/*    corner     |          steep slope
+		 *  z1      z2   |       z1             z2        */
+		{SLOPE_E, SLOPE_N, SLOPE_STEEP_E, SLOPE_STEEP_N}, // DIAGDIR_NE, z1 = E, z2 = N
+		{SLOPE_S, SLOPE_E, SLOPE_STEEP_S, SLOPE_STEEP_E}, // DIAGDIR_SE, z1 = S, z2 = E
+		{SLOPE_S, SLOPE_W, SLOPE_STEEP_S, SLOPE_STEEP_W}, // DIAGDIR_SW, z1 = S, z2 = W
+		{SLOPE_W, SLOPE_N, SLOPE_STEEP_W, SLOPE_STEEP_N}, // DIAGDIR_NW, z1 = W, z2 = N
+	};
+
+	if ((tileh & corners[edge][0]) != 0) *z1 += TILE_HEIGHT; // z1 is raised
+	if ((tileh & corners[edge][1]) != 0) *z2 += TILE_HEIGHT; // z2 is raised
+	if (tileh == corners[edge][2]) *z1 += TILE_HEIGHT; // z1 is highest corner of a steep slope
+	if (tileh == corners[edge][3]) *z2 += TILE_HEIGHT; // z2 is highest corner of a steep slope
+}
 
 static Slope GetFoundationSlope(TileIndex tile, uint* z)
 {
@@ -219,32 +245,34 @@ static Slope GetFoundationSlope(TileIndex tile, uint* z)
 static bool HasFoundationNW(TileIndex tile, Slope slope_here, uint z_here)
 {
 	uint z;
+
+	int z_W_here = z_here;
+	int z_N_here = z_here;
+	GetSlopeZOnEdge(slope_here, DIAGDIR_NW, &z_W_here, &z_N_here);
+
 	Slope slope = GetFoundationSlope(TILE_ADDXY(tile, 0, -1), &z);
+	int z_W = z;
+	int z_N = z;
+	GetSlopeZOnEdge(slope, DIAGDIR_SE, &z_W, &z_N);
 
-	return
-		(
-			z_here + (slope_here & SLOPE_N ? TILE_HEIGHT : 0) + (slope_here == SLOPE_STEEP_N ? TILE_HEIGHT : 0) >
-			z      + (slope      & SLOPE_E ? TILE_HEIGHT : 0) + (slope      == SLOPE_STEEP_E ? TILE_HEIGHT : 0)
-		) || (
-			z_here + (slope_here & SLOPE_W ? TILE_HEIGHT : 0) + (slope_here == SLOPE_STEEP_W ? TILE_HEIGHT : 0) >
-			z      + (slope      & SLOPE_S ? TILE_HEIGHT : 0) + (slope      == SLOPE_STEEP_S ? TILE_HEIGHT : 0)
-		);
+	return (z_N_here > z_N) || (z_W_here > z_W);
 }
 
 
 static bool HasFoundationNE(TileIndex tile, Slope slope_here, uint z_here)
 {
 	uint z;
+
+	int z_E_here = z_here;
+	int z_N_here = z_here;
+	GetSlopeZOnEdge(slope_here, DIAGDIR_NE, &z_E_here, &z_N_here);
+
 	Slope slope = GetFoundationSlope(TILE_ADDXY(tile, -1, 0), &z);
+	int z_E = z;
+	int z_N = z;
+	GetSlopeZOnEdge(slope, DIAGDIR_SW, &z_E, &z_N);
 
-	return
-		(
-			z_here + (slope_here & SLOPE_N ? TILE_HEIGHT : 0) + (slope_here == SLOPE_STEEP_N ? TILE_HEIGHT : 0) >
-			z      + (slope      & SLOPE_W ? TILE_HEIGHT : 0) + (slope      == SLOPE_STEEP_W ? TILE_HEIGHT : 0)
-		) || (
-			z_here + (slope_here & SLOPE_E ? TILE_HEIGHT : 0) + (slope_here == SLOPE_STEEP_E ? TILE_HEIGHT : 0) >
-			z      + (slope      & SLOPE_S ? TILE_HEIGHT : 0) + (slope      == SLOPE_STEEP_S ? TILE_HEIGHT : 0)
-		);
+	return (z_N_here > z_N) || (z_E_here > z_E);
 }
 
 
diff --git a/src/landscape.h b/src/landscape.h
index 5c9c813cb..a4b558384 100644
--- a/src/landscape.h
+++ b/src/landscape.h
@@ -25,6 +25,7 @@ bool IsValidTile(TileIndex tile);
 
 uint GetPartialZ(int x, int y, Slope corners);
 uint GetSlopeZ(int x, int y);
+void GetSlopeZOnEdge(Slope tileh, DiagDirection edge, int *z1, int *z2);
 
 static inline Point RemapCoords(int x, int y, int z)
 {
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
index 1bdd87ca2..255def8a9 100644
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -812,41 +812,59 @@ CommandCost DoConvertTunnelBridgeRail(TileIndex tile, RailType totype, bool exec
 }
 
 
-static void DrawBridgePillars(const PalSpriteID *psid, const TileInfo* ti, Axis axis, uint type, int x, int y, int z)
+/**
+ * Draws the pillars under high bridges.
+ *
+ * @param psid Image and palette of a bridge pillar.
+ * @param ti #TileInfo of current bridge-middle-tile.
+ * @param axis Orientation of bridge.
+ * @param type Bridge type.
+ * @param x Sprite X position of front pillar.
+ * @param y Sprite Y position of front pillar.
+ * @param z_bridge Absolute height of bridge bottom.
+ */
+static void DrawBridgePillars(const PalSpriteID *psid, const TileInfo* ti, Axis axis, uint type, int x, int y, int z_bridge)
 {
 	SpriteID image = psid->sprite;
 	if (image != 0) {
 		bool drawfarpillar = !HASBIT(GetBridgeFlags(type), 0);
-		int back_height, front_height;
-		int i = z;
-		const byte *p;
-
-		static const byte _tileh_bits[4][8] = {
-			{ 2, 1, 8, 4,  16,  2, 0, 9 },
-			{ 1, 8, 4, 2,   2, 16, 9, 0 },
-			{ 4, 8, 1, 2,  16,  2, 0, 9 },
-			{ 2, 4, 8, 1,   2, 16, 9, 0 }
-		};
 
-		p = _tileh_bits[(image & 1) * 2 + (axis == AXIS_X ? 0 : 1)];
-		front_height = ti->z + (ti->tileh & p[0] ? TILE_HEIGHT : 0);
-		back_height  = ti->z + (ti->tileh & p[1] ? TILE_HEIGHT : 0);
-
-		if (IsSteepSlope(ti->tileh)) {
-			if (!(ti->tileh & p[2])) front_height += TILE_HEIGHT;
-			if (!(ti->tileh & p[3])) back_height  += TILE_HEIGHT;
-		}
-
-		for (; z >= front_height || z >= back_height; z -= TILE_HEIGHT) {
-			/* HACK set height of the BB of pillars to 1, because the origin of the
-			 * sprites is at the top
-			 */
-			if (z >= front_height) { // front facing pillar
-				AddSortableSpriteToDraw(image, psid->pal, x, y, p[4], p[5], BB_HEIGHT_UNDER_BRIDGE - 5, z, HASBIT(_transparent_opt, TO_BRIDGES), 0, 0, -5);
+		/* "side" specifies the side the pillars stand on.
+		 * The length of the pillars is then set to the height of the bridge over the corners of this edge.
+		 *
+		 *                axis==AXIS_X  axis==AXIS_Y
+		 *   side==false      SW            NW
+		 *   side==true       NE            SE
+		 *
+		 * I have no clue, why this was done this way.
+		 */
+		bool side = HASBIT(image, 0);
+
+		/* "dir" means the edge the pillars stand on */
+		DiagDirection dir = AxisToDiagDir(axis);
+		if (side != (axis == AXIS_Y)) dir = ReverseDiagDir(dir);
+
+		/* Determine ground height under pillars */
+		int front_height = ti->z;
+		int back_height = ti->z;
+		GetSlopeZOnEdge(ti->tileh, dir, &front_height, &back_height);
+
+		/* x and y size of bounding-box of pillars */
+		int w = (axis == AXIS_X ? 16 : 2);
+		int h = (axis == AXIS_X ? 2 : 16);
+		/* sprite position of back facing pillar */
+		int x_back = x - (axis == AXIS_X ? 0 : 9);
+		int y_back = y - (axis == AXIS_X ? 9 : 0);
+
+		for (int cur_z = z_bridge; cur_z >= front_height || cur_z >= back_height; cur_z -= TILE_HEIGHT) {
+			/* Draw front facing pillar */
+			if (cur_z >= front_height) {
+				AddSortableSpriteToDraw(image, psid->pal, x, y, w, h, BB_HEIGHT_UNDER_BRIDGE - 5, cur_z, HASBIT(_transparent_opt, TO_BRIDGES), 0, 0, -5);
 			}
 
-			if (drawfarpillar && z >= back_height && z < i - TILE_HEIGHT) { // back facing pillar
-				AddSortableSpriteToDraw(image, psid->pal, x - p[6], y - p[7], p[4], p[5], BB_HEIGHT_UNDER_BRIDGE - 5, z, HASBIT(_transparent_opt, TO_BRIDGES), 0, 0, -5);
+			/* Draw back facing pillar, but not the highest part directly under the bridge-floor */
+			if (drawfarpillar && cur_z >= back_height && cur_z < z_bridge - TILE_HEIGHT) {
+				AddSortableSpriteToDraw(image, psid->pal, x_back, y_back, w, h, BB_HEIGHT_UNDER_BRIDGE - 5, cur_z, HASBIT(_transparent_opt, TO_BRIDGES), 0, 0, -5);
 			}
 		}
 	}