4 files changed, 26 insertions, 51 deletions

diff --git a/src/smallmap_gui.cpp b/src/smallmap_gui.cpp
index dea0caa39..b9bbe4e25 100644
--- a/src/smallmap_gui.cpp
+++ b/src/smallmap_gui.cpp
@@ -900,30 +900,6 @@ void SmallMapWindow::DrawTowns(const DrawPixelInfo *dpi) const
 }
 
 /**
- * Convert a coordinate of the viewport to essentially a tile on the map,
- * taking care of the different location due to height.
- * @param viewport_coord The coordinate in the viewport.
- * @return The tile location.
- */
-Point SmallMapWindow::GetSmallMapCoordIncludingHeight(Point viewport_coord) const
-{
-	/* First find out which tile would be there if we ignore height */
-	Point pt = InverseRemapCoords(viewport_coord.x, viewport_coord.y);
-	Point pt_without_height = {pt.x / TILE_SIZE, pt.y / TILE_SIZE};
-
-	/* Problem: There are mountains.  So the tile actually displayed at the given position
-	 * might be the high mountain of 30 tiles south.
-	 * Unfortunately, there is no closed formula for finding such a tile.
-	 * We call GetRowAtTile originally implemented for the viewport code, which performs
-	 * a interval search.  For details, see its documentation. */
-	int row_without_height = pt_without_height.x + pt_without_height.y;
-	int row_with_height = GetRowAtTile(viewport_coord.y, pt_without_height, false);
-	int row_offset = row_with_height - row_without_height;
-	Point pt_with_height = {pt_without_height.x + row_offset / 2, pt_without_height.y + row_offset / 2};
-	return pt_with_height;
-}
-
-/**
  * Adds map indicators to the smallmap.
  */
 void SmallMapWindow::DrawMapIndicators() const
@@ -931,15 +907,13 @@ void SmallMapWindow::DrawMapIndicators() const
 	/* Find main viewport. */
 	const ViewPort *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
 
-	Point upper_left_viewport_coord = {vp->virtual_left, vp->virtual_top};
-	Point upper_left_small_map_coord = GetSmallMapCoordIncludingHeight(upper_left_viewport_coord);
-	Point upper_left = this->RemapTile(upper_left_small_map_coord.x, upper_left_small_map_coord.y);
+	Point upper_left_smallmap_coord  = TranslateXYToTileCoord(vp, vp->left, vp->top, false);
+	Point lower_right_smallmap_coord = TranslateXYToTileCoord(vp, vp->left + vp->width - 1, vp->top + vp->height - 1, false);
+
+	Point upper_left = this->RemapTile(upper_left_smallmap_coord.x / (int)TILE_SIZE, upper_left_smallmap_coord.y / (int)TILE_SIZE);
 	upper_left.x -= this->subscroll;
 
-	Point lower_right_viewport_coord = {vp->virtual_left + vp->virtual_width, vp->virtual_top + vp->virtual_height};
-	Point lower_right_smallmap_coord = GetSmallMapCoordIncludingHeight(lower_right_viewport_coord);
-	Point lower_right = this->RemapTile(lower_right_smallmap_coord.x, lower_right_smallmap_coord.y);
-	/* why do we do this? in my tests subscroll was zero */
+	Point lower_right = this->RemapTile(lower_right_smallmap_coord.x / (int)TILE_SIZE, lower_right_smallmap_coord.y / (int)TILE_SIZE);
 	lower_right.x -= this->subscroll;
 
 	SmallMapWindow::DrawVertMapIndicator(upper_left.x, upper_left.y, lower_right.y);
@@ -1662,19 +1636,12 @@ void SmallMapWindow::SetNewScroll(int sx, int sy, int sub)
  */
 void SmallMapWindow::SmallMapCenterOnCurrentPos()
 {
-	/* Goal: Given the viewport coordinates of the middle of the map window, find
-	 * out which tile is displayed there. */
-
-	/* First find out which tile would be there if we ignore height */
 	const ViewPort *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
-	Point viewport_center = {vp->virtual_left + vp->virtual_width  / 2, vp->virtual_top  + vp->virtual_height / 2};
-	Point pt_with_height = GetSmallMapCoordIncludingHeight(viewport_center);
-
-	/* And finally scroll to that position. */
+	Point viewport_center = TranslateXYToTileCoord(vp, vp->left + vp->width / 2, vp->top + vp->height / 2);
 
 	int sub;
 	const NWidgetBase *wid = this->GetWidget<NWidgetBase>(WID_SM_MAP);
-	Point sxy = this->ComputeScroll(pt_with_height.x, pt_with_height.y,
+	Point sxy = this->ComputeScroll(viewport_center.x / (int)TILE_SIZE, viewport_center.y / (int)TILE_SIZE,
 			max(0, (int)wid->current_x / 2 - 2), wid->current_y / 2, &sub);
 	this->SetNewScroll(sxy.x, sxy.y, sub);
 	this->SetDirty();
diff --git a/src/smallmap_gui.h b/src/smallmap_gui.h
index 7a4805841..2903544a6 100644
--- a/src/smallmap_gui.h
+++ b/src/smallmap_gui.h
@@ -157,7 +157,6 @@ protected:
 	void DrawSmallMapColumn(void *dst, uint xc, uint yc, int pitch, int reps, int start_pos, int end_pos, Blitter *blitter) const;
 	void DrawVehicles(const DrawPixelInfo *dpi, Blitter *blitter) const;
 	void DrawTowns(const DrawPixelInfo *dpi) const;
-	Point GetSmallMapCoordIncludingHeight(Point viewport_coord) const;
 	void DrawSmallMap(DrawPixelInfo *dpi) const;
 
 	Point RemapTile(int tile_x, int tile_y) const;
diff --git a/src/viewport.cpp b/src/viewport.cpp
index 796368114..3fc14fcc7 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -405,9 +405,10 @@ ViewPort *IsPtInWindowViewport(const Window *w, int x, int y)
  * @param vp  Viewport that contains the (\a x, \a y) screen coordinate
  * @param x   Screen x coordinate
  * @param y   Screen y coordinate
+ * @param clamp_to_map Clamp the coordinate outside of the map to the closest tile within the map.
  * @return Tile coordinate
  */
-static Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y)
+Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y, bool clamp_to_map)
 {
 	Point pt;
 	int a, b;
@@ -425,13 +426,15 @@ static Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y)
 	a = y - x;
 	b = y + x;
 
-	/* Bring the coordinates near to a valid range. This is mostly due to the
-	 * tiles on the north side of the map possibly being drawn too high due to
-	 * the extra height levels. So at the top we allow a number of extra tiles.
-	 * This number is based on the tile height and pixels. */
-	int extra_tiles = CeilDiv(_settings_game.construction.max_heightlevel * TILE_HEIGHT, TILE_PIXELS);
-	a = Clamp(a, -extra_tiles * TILE_SIZE, MapMaxX() * TILE_SIZE - 1);
-	b = Clamp(b, -extra_tiles * TILE_SIZE, MapMaxY() * TILE_SIZE - 1);
+	if (clamp_to_map) {
+		/* Bring the coordinates near to a valid range. This is mostly due to the
+		 * tiles on the north side of the map possibly being drawn too high due to
+		 * the extra height levels. So at the top we allow a number of extra tiles.
+		 * This number is based on the tile height and pixels. */
+		int extra_tiles = CeilDiv(_settings_game.construction.max_heightlevel * TILE_HEIGHT, TILE_PIXELS);
+		a = Clamp(a, -extra_tiles * TILE_SIZE, MapMaxX() * TILE_SIZE - 1);
+		b = Clamp(b, -extra_tiles * TILE_SIZE, MapMaxY() * TILE_SIZE - 1);
+	}
 
 	/* (a, b) is the X/Y-world coordinate that belongs to (x,y) if the landscape would be completely flat on height 0.
 	 * Now find the Z-world coordinate by fix point iteration.
@@ -448,8 +451,13 @@ static Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y)
 	for (int malus = 3; malus > 0; malus--) z = GetSlopePixelZ(Clamp(a + max(z, malus) - malus, min_coord, MapMaxX() * TILE_SIZE - 1), Clamp(b + max(z, malus) - malus, min_coord, MapMaxY() * TILE_SIZE - 1)) / 2;
 	for (int i = 0; i < 5; i++) z = GetSlopePixelZ(Clamp(a + z, min_coord, MapMaxX() * TILE_SIZE - 1), Clamp(b + z, min_coord, MapMaxY() * TILE_SIZE - 1)) / 2;
 
-	pt.x = Clamp(a + z, min_coord, MapMaxX() * TILE_SIZE - 1);
-	pt.y = Clamp(b + z, min_coord, MapMaxY() * TILE_SIZE - 1);
+	if (clamp_to_map) {
+		pt.x = Clamp(a + z, min_coord, MapMaxX() * TILE_SIZE - 1);
+		pt.y = Clamp(b + z, min_coord, MapMaxY() * TILE_SIZE - 1);
+	} else {
+		pt.x = a + z;
+		pt.y = b + z;
+	}
 
 	return pt;
 }
diff --git a/src/viewport_func.h b/src/viewport_func.h
index 8dbbc5945..3525fd6a2 100644
--- a/src/viewport_func.h
+++ b/src/viewport_func.h
@@ -25,6 +25,7 @@ void SetSelectionRed(bool);
 void DeleteWindowViewport(Window *w);
 void InitializeWindowViewport(Window *w, int x, int y, int width, int height, uint32 follow_flags, ZoomLevel zoom);
 ViewPort *IsPtInWindowViewport(const Window *w, int x, int y);
+Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y, bool clamp_to_map = true);
 Point GetTileBelowCursor();
 void UpdateViewportPosition(Window *w);