Fix tileset being completely cleared when resizing a project

Now only remove the tiles that are used so they can be remade as resized tiles. Unused tiles remain in the tileset as is.

src/Autoload/OpenSave.gd

@@ -287,7 +287,10 @@ func open_pxo_file(path: String, is_backup := false, replace_empty := true) -> v
 					var image := Image.create_from_data(
 						tile_size.x, tile_size.y, false, new_project.get_image_format(), image_data
 					)
-					tileset.add_tile(image, null)
+					tileset.add_tile(image, null, 0)
+			for cel in new_project.get_all_pixel_cels():
+				if cel is CelTileMap:
+					cel.find_times_used_of_tiles()
 		zip_reader.close()
 	new_project.export_directory_path = path.get_base_dir()
 
@@ -878,7 +881,7 @@ func open_image_as_tileset(
 				Rect2i(frame_width * xx, frame_height * yy, frame_width, frame_height)
 			)
 			@warning_ignore("int_as_enum_without_cast")
-			tileset.add_tile(cropped_image, null)
+			tileset.add_tile(cropped_image, null, 0)
 	project.tilesets.append(tileset)
 
 
@@ -901,7 +904,7 @@ func open_image_as_tileset_smart(
 		)
 		cropped_image.blit_rect(image, rect, offset)
 		@warning_ignore("int_as_enum_without_cast")
-		tileset.add_tile(cropped_image, null)
+		tileset.add_tile(cropped_image, null, 0)
 	project.tilesets.append(tileset)
 
 

src/Classes/Cels/CelTileMap.gd

@@ -330,7 +330,7 @@ func serialize_undo_data_source_image(
 	if source_image.get_size() != image.get_size():
 		undo_data[self]["resize"] = true
 		_resize_cells(source_image.get_size())
-		tileset.clear_tileset(self)
+		tileset.handle_project_resize(self)
 	var tile_editing_mode := TileSetPanel.tile_editing_mode
 	if tile_editing_mode == TileSetPanel.TileEditingMode.MANUAL:
 		tile_editing_mode = TileSetPanel.TileEditingMode.AUTO
@@ -352,6 +352,13 @@ func deserialize_undo_data(dict: Dictionary, undo_redo: UndoRedo, undo: bool) ->
 			undo_redo.add_do_method(tileset.deserialize_undo_data.bind(dict.tileset, self))
 
 
+## Called when loading a new project. Loops through all [member cells]
+## and finds the amount of times each tile from the [member tileset] is being used.
+func find_times_used_of_tiles() -> void:
+	for cell in cells:
+		tileset.tiles[cell.index].times_used += 1
+
+
 ## Gets called every time a change is being applied to the [param image],
 ## such as when finishing drawing with a draw tool, or when applying an image effect.
 ## This method responsible for updating the indices of the [member cells], as well as

src/Classes/TileSetCustom.gd

@@ -16,9 +16,9 @@ var name := ""
 var tile_size: Vector2i
 ## The collection of tiles in the form of an [Array] of type [TileSetCustom.Tile].
 var tiles: Array[Tile] = []
-## If [code]true[/code], the code in [method clear_tileset] does not execute.
+## If [code]true[/code], the code in [method handle_project_resize] does not execute.
 ## This variable is used to prevent multiple cels from clearing the tileset at the same time.
-## In [method clear_tileset], the variable is set to [code]true[/code], and then
+## In [method handle_project_resize], the variable is set to [code]true[/code], and then
 ## immediately set to [code]false[/code] in the next frame using [method Object.set_deferred].
 var _tileset_has_been_cleared := false
 
@@ -50,8 +50,9 @@ func _init(_tile_size: Vector2i, _name := "", add_empty_tile := true) -> void:
 ## Adds a new [param image] as a tile to the tileset.
 ## The [param cel] parameter references the [CelTileMap] that this change is coming from,
 ## and the [param edit_mode] parameter contains the tile editing mode at the time of this change.
-func add_tile(image: Image, cel: CelTileMap) -> void:
+func add_tile(image: Image, cel: CelTileMap, times_used := 1) -> void:
 	var tile := Tile.new(image)
+	tile.times_used = times_used
 	tiles.append(tile)
 	updated.emit(cel, -1)
 
@@ -115,14 +116,15 @@ func remove_unused_tiles(cel: CelTileMap) -> bool:
 	return tile_removed
 
 
-## Clears the tileset. Usually called when the project gets resized,
+## Clears the used tiles of tileset. Called when the project gets resized,
 ## and tilemap cels are updating their size and clearing the tileset to re-create it.
-func clear_tileset(cel: CelTileMap) -> void:
+func handle_project_resize(cel: CelTileMap) -> void:
 	if _tileset_has_been_cleared:
 		return
-	tiles.clear()
-	var empty_image := Image.create_empty(tile_size.x, tile_size.y, false, Image.FORMAT_RGBA8)
-	tiles.append(Tile.new(empty_image))
+	for i in range(tiles.size() - 1, 0, -1):
+		var tile := tiles[i]
+		if tile.times_used > 0:
+			tiles.erase(tile)
 	updated.emit(cel, -1)
 	_tileset_has_been_cleared = true
 	set_deferred("_tileset_has_been_cleared", false)