Trees GUI improvements

src/lang/english.txt

@@ -2542,13 +2542,19 @@ STR_OBJECT_BUILD_SIZE                                           :{BLACK}Size: {G
 STR_OBJECT_CLASS_LTHS                                           :Lighthouses
 STR_OBJECT_CLASS_TRNS                                           :Transmitters
 
-# Tree planting window (last two for SE only)
+# Tree planting window (last eight for SE only)
 STR_PLANT_TREE_CAPTION                                          :{WHITE}Trees
 STR_PLANT_TREE_TOOLTIP                                          :{BLACK}Select tree type to plant. If the tile already has a tree, this will add more trees of mixed types independent of the selected type
 STR_TREES_RANDOM_TYPE                                           :{BLACK}Trees of random type
 STR_TREES_RANDOM_TYPE_TOOLTIP                                   :{BLACK}Place trees of random type. Shift toggles building/showing cost estimate
 STR_TREES_RANDOM_TREES_BUTTON                                   :{BLACK}Random Trees
 STR_TREES_RANDOM_TREES_TOOLTIP                                  :{BLACK}Plant trees randomly throughout the landscape
+STR_TREES_MODE_NORMAL_BUTTON                                    :{BLACK}Normal
+STR_TREES_MODE_NORMAL_TOOLTIP                                   :{BLACK}Plant single trees by dragging over the landscape.
+STR_TREES_MODE_FOREST_SM_BUTTON                                 :{BLACK}Grove
+STR_TREES_MODE_FOREST_SM_TOOLTIP                                :{BLACK}Plant small forests by dragging over the landscape.
+STR_TREES_MODE_FOREST_LG_BUTTON                                 :{BLACK}Forest
+STR_TREES_MODE_FOREST_LG_TOOLTIP                                :{BLACK}Plant large forests by dragging over the landscape.
 
 # Land generation window (SE)
 STR_TERRAFORM_TOOLBAR_LAND_GENERATION_CAPTION                   :{WHITE}Land Generation

src/tilehighlight_func.h

@@ -22,6 +22,7 @@ void SetObjectToPlace(CursorID icon, PaletteID pal, HighLightStyle mode, WindowC
 void ResetObjectToPlace();
 
 void VpSelectTilesWithMethod(int x, int y, ViewportPlaceMethod method);
+void VpStartDragging(ViewportDragDropSelectionProcess process);
 void VpStartPlaceSizing(TileIndex tile, ViewportPlaceMethod method, ViewportDragDropSelectionProcess process);
 void VpSetPresizeRange(TileIndex from, TileIndex to);
 void VpSetPlaceSizingLimit(int limit);

src/tree_cmd.cpp

@@ -290,6 +290,51 @@ void PlaceTreesRandomly()
 	}
 }
 
+/**
+ * Place some trees in a radius around a tile.
+ * The trees are placed in an quasi-normal distribution around the indicated tile, meaning that while
+ * the radius does define a square, the distribution inside the square will be roughly circular.
+ * @note This function the interactive RNG and must only be used in editor and map generation.
+ * @param tile      Tile to place trees around.
+ * @param treetype  Type of trees to place. Must be a valid tree type for the climate.
+ * @param radius    Maximum distance (on each axis) from tile to place trees.
+ * @param count     Maximum number of trees to place.
+ * @return Number of trees actually placed.
+ */
+uint PlaceTreeGroupAroundTile(TileIndex tile, TreeType treetype, uint radius, uint count)
+{
+	assert(treetype < TREE_TOYLAND + TREE_COUNT_TOYLAND);
+	const bool allow_desert = treetype == TREE_CACTUS;
+	uint planted = 0;
+
+	for (; count > 0; count--) {
+		/* Simple quasi-normal distribution with range [-radius; radius) */
+		auto mkcoord = [&]() -> int32 {
+			const uint32 rand = InteractiveRandom();
+			const int32 dist = GB<int32>(rand, 0, 8) + GB<int32>(rand, 8, 8) + GB<int32>(rand, 16, 8) + GB<int32>(rand, 24, 8);
+			const int32 scu = dist * radius / 512;
+			return scu - radius;
+		};
+		const int32 xofs = mkcoord();
+		const int32 yofs = mkcoord();
+		const TileIndex tile_to_plant = TileAddWrap(tile, xofs, yofs);
+		if (tile_to_plant != INVALID_TILE) {
+			if (IsTileType(tile_to_plant, MP_TREES) && GetTreeCount(tile_to_plant) < 4) {
+				AddTreeCount(tile_to_plant, 1);
+				SetTreeGrowth(tile_to_plant, 0);
+				MarkTileDirtyByTile(tile_to_plant, 0);
+				planted++;
+			} else if (CanPlantTreesOnTile(tile_to_plant, allow_desert)) {
+				PlantTreesOnTile(tile_to_plant, treetype, 0, 3);
+				MarkTileDirtyByTile(tile_to_plant, 0);
+				planted++;
+			}
+		}
+	}
+
+	return planted;
+}
+
 /**
  * Place new trees.
  *
@@ -349,7 +394,7 @@ CommandCost CmdPlantTree(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 		switch (GetTileType(tile)) {
 			case MP_TREES:
 				/* no more space for trees? */
-				if (_game_mode != GM_EDITOR && GetTreeCount(tile) == 4) {
+				if (GetTreeCount(tile) == 4) {
 					msg = STR_ERROR_TREE_ALREADY_HERE;
 					continue;
 				}