TI-Nspire Lua Editor: Try Your Own

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Lua and JavaScript

Scripting Tutorial - Lesson 13: Classes and Keyboard Controls

Play with the script in the text box below, and then click the "run your code" button above.

platform.apilevel = '1.0'

local screen = platform.window
		local w = screen:width()
		local h = screen:height()
		local TrackedObject = nil
		
		local Color = {
		red 	 = {0xFF, 0x00, 0x00},
		green	 = {0x00, 0xFF, 0x00},
		}

function on.resize()

w = platform.window:width()
		    h = platform.window:height()

TrackedObject = nil
		    Sq = Square(w/2, h/2, h/3, h/3)

end

Square = class()

function Square:init(x, y, width, height)
			self.x	 = x
			self.y	 = y
			self.width	= width or 20
			self.height	= height or 20
			self.color = Color.green
			self.selected = false
		end

function Square:contains(x, y)
			local sw = self.width
			local sh = self.height
			return x >= self.x - sw/2 and x <= self.x + sw/2 and
				y >= self.y - sh/2 and y <= self.y + sh/2
		end

function Square:paint(gc)
			gc:setColorRGB(unpack(self.color))
			gc:fillRect(self.x - self.width / 2, self.y - self.height / 2, 
						self.width, self.height)
			if self.selected then
				gc:setPen("medium","smooth")
				gc:setColorRGB(0, 0, 0)
				gc:drawRect(self.x - self.width / 2, self.y - self.height / 2, 
							self.width, self.height)
			end
		end

function on.mouseDown(x,y)
			if Sq:contains(x, y) then
				if TrackedObject ~= nil then
					TrackedObject.selected = false
				end

TrackedObject = Sq
				Sq.selected = true
			
				screen:invalidate()
			end
		end

function on.mouseUp(x,y)
		
			if not Sq:contains(x, y) then
				Sq.x = x
				Sq.y = y
			end
		
			if TrackedObject ~= nil then		
				TrackedObject.selected = false
			end

TrackedObject = nil
			screen:invalidate()
		end			
		
		function on.mouseMove(x,y)
			if TrackedObject ~= nil then
				TrackedObject.x = x
				TrackedObject.y = y

screen:invalidate()
			end
		end

function on.arrowRight()
			if Sq.x < w - Sq.width / 2 then
				Sq.x = Sq.x + 5
				screen:invalidate()
			end
		end

function on.arrowLeft()
			if Sq.x > Sq.width / 2 then
				Sq.x = Sq.x - 5
				screen:invalidate()
			end
		end

function on.arrowDown()
			if Sq.y < h - Sq.height / 2 then
				Sq.y = Sq.y + 5
				screen:invalidate()
			end
		end

function on.arrowUp()
			if Sq.y > Sq.height / 2 then
				Sq.y = Sq.y - 5
				screen:invalidate()
				end
		end

function on.paint(gc)
			w = screen:width()
			h = screen:height()

Sq:paint(gc)
			
			gc:setFont("sansserif", "b", 10)
			gc:setColorRGB(unpack(Sq.color))
			gc:drawString(
					"("..Sq.x..","
					..Sq.y..")",w/10,h/10)
		end

Click "run your code!" to get started.

You can copy and paste the script (or type your own) into the lower text box and then click "run your code!" After that, explore and experiment!

Look at how this script has been adapted for the browser context. Since we have no tab or escape key controls, then there is no way to define a "TrackedObject" using the keyboard - we can only use the arrow keys to move the object. Look closely at how this movement has been limited to prevent the square from moving off the visible window.

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