LOVE2D Grid Selection With A*

grid.lua

-- rounds a number to the nearest multiple of cell_size
-- for determining a cell in the grid
function grid_coords(n)
  return math.floor(n / cell_size) * cell_size;
end

function love.conf(t)
	t.title = "Worldthing"
	t.author = "sli"
	t.modules.physics = false
	t.modules.joystick = false
end

function love.load()
	cell_size = 50
	cell_tl_x = 0
	cell_tl_y = 0
	selected_cell_x = 0
	selected_cell_y = 0
	cell_selected = false
	w = love.graphics.getWidth()
	h = love.graphics.getHeight()
	grid_w = w / 10
	grid_h = h / 10
end

function love.mousepressed(x, y, button)
	-- select a cell with the left mouse button
	if button == "l" then
		cell_selected = true
		selected_cell_x = grid_coords(x)
		selected_cell_y = grid_coords(y)
	end
end

function love.draw()
	love.graphics.setColor(255, 255, 255, 255)

	-- draw rows
	for r=0,grid_h do
		love.graphics.line(0, r*cell_size, w, r*cell_size)
	end

	-- draw columns
	for c=0,grid_w do
		love.graphics.line(c*cell_size, 0, c*cell_size, h)
	end

	-- draw selected cell, if available
	if cell_selected then
		love.graphics.setColor(0, 0, 255, 255)
		love.graphics.rectangle("fill", selected_cell_x, selected_cell_y, cell_size, cell_size)
	end

	-- highlight mouse cursor cell
	love.graphics.setColor(255, 255, 255, 64)
	love.graphics.rectangle("fill", cell_tl_x, cell_tl_y, cell_size, cell_size)
end

function love.update(dt)
	mouse_x, mouse_y = love.mouse.getPosition()

	-- find mouse's position in the grid
	cell_tl_x = grid_coords(mouse_x);
	cell_tl_y = grid_coords(mouse_y);
end