Fix plans/route line viewport mark dirty not being wide enough

src/viewport.cpp

@@ -3703,12 +3703,15 @@ void MarkTileLineDirty(const TileIndex from_tile, const TileIndex to_tile, Viewp
 	const Point from_pt = RemapCoords2(TileX(from_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(from_tile) * TILE_SIZE + TILE_SIZE / 2);
 	const Point to_pt = RemapCoords2(TileX(to_tile) * TILE_SIZE + TILE_SIZE / 2, TileY(to_tile) * TILE_SIZE + TILE_SIZE / 2);
 
-	const int block_radius = 20;
+	for (Viewport * const vp : _viewport_window_cache) {
+		if (flags & VMDF_NOT_MAP_MODE && vp->zoom >= ZOOM_LVL_DRAW_MAP) continue;
 
-	int x1 = from_pt.x / block_radius;
+		const int block_shift = 2 + vp->zoom;
-	int y1 = from_pt.y / block_radius;
+
-	const int x2 = to_pt.x / block_radius;
+		int x1 = from_pt.x >> block_shift;
-	const int y2 = to_pt.y / block_radius;
+		int y1 = from_pt.y >> block_shift;
+		const int x2 = to_pt.x >> block_shift;
+		const int y2 = to_pt.y >> block_shift;
 
 		/* http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm#Simplification */
 		const int dx = abs(x2 - x1);
@@ -3717,11 +3720,12 @@ void MarkTileLineDirty(const TileIndex from_tile, const TileIndex to_tile, Viewp
 		const int sy = (y1 < y2) ? 1 : -1;
 		int err = dx - dy;
 		for (;;) {
-		MarkAllViewportsDirty(
+			MarkViewportDirty(
-				(x1 - 1) * block_radius,
+					vp,
-				(y1 - 1) * block_radius,
+					(x1 - 1) << block_shift,
-				(x1 + 1) * block_radius,
+					(y1 - 1) << block_shift,
-				(y1 + 1) * block_radius,
+					(x1 + 2) << block_shift,
+					(y1 + 2) << block_shift,
 					flags
 			);
 			if (x1 == x2 && y1 == y2) break;
@@ -3736,6 +3740,7 @@ void MarkTileLineDirty(const TileIndex from_tile, const TileIndex to_tile, Viewp
 			}
 		}
 	}
+}
 
 static void MarkRoutePathsDirty(const std::vector<DrawnPathRouteTileLine> &lines)
 {