Add drag painting to level editor

level_editor/editor.lua

@@ -44,6 +44,57 @@ local assetSearchText = ""
 local assetSearchButtons = {}
 local worldSearchText = ""
 local worldSearchBox = { x = 10, y = 34, w = 0, h = 28 }
+local roomBrush = nil
+
+-- Convert a pointer position into a valid room cell. Keeping brush state in
+-- cell coordinates means a click that jitters within a tile cannot place or
+-- erase that tile more than once.
+local function roomCellAt(x, y)
+	if x < 0 or x >= width or y < 0 or y >= height then return nil end
+	local cell = currentRoom:getCellFromMousePos(x, y)
+	cell.x = constrain(cell.x, 1, gridWidth)
+	cell.y = constrain(cell.y, 1, gridHeight)
+	return cell
+end
+
+local function paintRoomCell(cell, button)
+	-- Use the centre of the cell so Room's existing pointer-based edit helpers
+	-- perform the same operation as a normal click.
+	local x = (cell.x - .5) * width / gridWidth
+	local y = (cell.y - .5) * height / gridHeight
+	if button == 1 and selectedAsset then
+		currentRoom:attemptPlace(selectedAsset, gameAssets[selectedAsset], x, y, selectedColor)
+	elseif button == 2 then
+		currentRoom:attemptDelete(x, y, selectedColor)
+	end
+end
+
+local function paintRoomLine(from, to, button)
+	-- Bresenham keeps a fast mouse movement from leaving holes between the
+	-- cells that happened to receive mouse-move events.
+	local x, y = from.x, from.y
+	local dx, dy = math.abs(to.x - x), math.abs(to.y - y)
+	local stepX = x < to.x and 1 or -1
+	local stepY = y < to.y and 1 or -1
+	local err = dx - dy
+
+	while true do
+		if x ~= from.x or y ~= from.y then paintRoomCell({ x = x, y = y }, button) end
+		if x == to.x and y == to.y then break end
+		local twiceErr = err * 2
+		if twiceErr > -dy then err = err - dy; x = x + stepX end
+		if twiceErr < dx then err = err + dx; y = y + stepY end
+	end
+end
+
+local function beginRoomBrush(x, y, button)
+	if button ~= 1 and button ~= 2 then return end
+	if button == 1 and not selectedAsset then return end
+	local cell = roomCellAt(x, y)
+	if not cell then return end
+	paintRoomCell(cell, button)
+	roomBrush = { button = button, lastCell = cell }
+end
 
 -- ── Room-view sidebar layout ────────────────────────────────────────────────
 -- Declared up here (not next to editorDraw) so editorMouseHandler, defined
@@ -730,8 +781,8 @@ function editorMouseHandler(x, y, button)
 		end
 	else
 		-- click landed on the grid (game area): place the selected asset
-		if editorView == "room" and button == 1 and selectedAsset then
-			currentRoom:attemptPlace(selectedAsset, gameAssets[selectedAsset], x, y, selectedColor)
+		if editorView == "room" then
+			beginRoomBrush(x, y, button)
 		elseif editorView == "world" then
 			local cellX, cellY = gameWorld:getCellFromMousePos(x, y)
 			if not gameWorld:isInBounds(cellX, cellY) then return end
@@ -748,6 +799,30 @@ function editorMouseHandler(x, y, button)
 	end
 end
 
+function editorMouseMoved(x, y)
+	if not roomBrush then return end
+	if editorView ~= "room" then
+		roomBrush = nil
+		return
+	end
+
+	local cell = roomCellAt(x, y)
+	if not cell then
+		-- Leaving the grid ends this stroke; re-entering should not draw a line
+		-- across the sidebar or outside of the level.
+		roomBrush = nil
+		return
+	end
+	if cell.x == roomBrush.lastCell.x and cell.y == roomBrush.lastCell.y then return end
+
+	paintRoomLine(roomBrush.lastCell, cell, roomBrush.button)
+	roomBrush.lastCell = cell
+end
+
+function editorMouseReleased(_, _, button)
+	if roomBrush and roomBrush.button == button then roomBrush = nil end
+end
+
 function editorTextHandler(text)
 	if editorView == "asset" and activeField then
 		inputText = text
@@ -809,6 +884,11 @@ function editorDraw()
 				item.x, item.y = s.list.pos(i)
 				item.w = s.listRect.w
 				item:draw()
+				if item.name == "asset" and item.text == selectedAsset then
+					love.graphics.setColor(1, 0.85, 0.2, 1)
+					love.graphics.setLineWidth(3)
+					love.graphics.rectangle("line", item.x + 1, item.y + 1, item.w - 2, item.h - 2)
+				end
 			end
 		end
 		Layout.unclip()