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Lua and JavaScript

Scripting Tutorial - Lesson 15: Putting it all together

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

Colour = { 
		 red   = {0xFF, 0x00, 0x00}, 
		 green  = {0x00, 0xFF, 0x00}, 
		}

TrackedObject = nil 
		TrackOffsetx = 0 
		TrackOffsety = 0 
		    w = platform.window:width() 
		    h = platform.window:height()

function on.resize()

w = platform.window:width() 
		    h = platform.window:height() 
		    platform.window:invalidate() 
		    Objects = { 
		 Circle(0.9*w, h/3, w/20, w/20), 
		 Square(0.9*w, 2*h/3, w/10, w/10), 
		} 
		    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.colour = Colour.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.colour)) 
		 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

Circle = class()

function Circle:init(x, y, width, height) 
		 self.x = x 
		 self.y = y 
		 self.width = width * 2 
		 self.height = height * 2 
		 self.radius = height 
		 self.colour = Colour.red 
		 self.selected = false 
		end

function Circle:contains(x, y) 
		 local r = self.radius 
		 local d = math.sqrt((self.x - x)^2 + (self.y - y)^2) 
		 return d <= r 
		end

function Circle:paint(gc) 
		 local cx = self.x - self.radius 
		 local cy = self.y - self.radius 
		 local diameter = 2*self.radius 
		 gc:setColorRGB(unpack(self.colour)) 
		 gc:fillArc(cx, cy, diameter, diameter, 0, 360) 
		 if self.selected then 
		     gc:setPen("medium","smooth") 
		     gc:setColorRGB(0, 0, 0) 
		 gc:drawArc(cx, cy, diameter, diameter, 0, 360) 
		    end

end

Objects = { 
		 Circle(0.9*w, h/3, w/20, w/20), 
		 Square(0.9*w, 2*h/3, w/10, w/10), 
		}

function on.tabKey()

if TrackedObject ~= nil then 
		          TrackedObject.selected = false 
		          end

for i = #Objects, 1, -1 do 
		     local obj = Objects[i]

if obj == TrackedObject  then 
		             TrackedObject = Objects[i+1] 
		             break 
		         end 
		    end

if TrackedObject == nil then 
		         TrackedObject = Objects[1] 
		         end

TrackedObject.selected = true 
		   platform.window:invalidate()

end

function on.arrowRight()

if TrackedObject ~= nil then 
		    if TrackedObject.x < w - TrackedObject.width / 2 then 
		        TrackedObject.x = TrackedObject.x + 5 
		        end 
		    end

end

function on.arrowLeft()

if TrackedObject ~= nil then 
		    if TrackedObject.x > TrackedObject.width / 2 then 
		        TrackedObject.x = TrackedObject.x - 5 
		        end 
		    end

end

function on.arrowDown()

if TrackedObject ~= nil then 
		    if TrackedObject.y < h - TrackedObject.height / 2 then 
		        TrackedObject.y = TrackedObject.y + 5 
		        end 
		    end

end

function on.arrowUp()

if TrackedObject ~= nil then 
		    if TrackedObject.y > TrackedObject.height / 2 then 
		        TrackedObject.y = TrackedObject.y - 5 
		        end 
		    end

end

function on.escapeKey()

Objects = { 
		 Circle(0.9*w, h/3, w/20, w/20), 
		 Square(0.9*w, 2*h/3, w/10, w/10), 
		}

if TrackedObject ~= nil then 
		            TrackedObject.selected= false 
		            TrackedObject = nil 
		            end 
		end

function on.enterKey() 
		 if TrackedObject ~= nil then 
		   if TrackedObject.colour == Colour.green then 
		       table.insert(Objects, Square(TrackedObject.x, TrackedObject.y, w/10, w/10)) 
		   else 
		       table.insert(Objects, Circle(TrackedObject.x, TrackedObject.y, w/20, w/20)) 
		   end 
		        end 
		end

function on.mouseDown(x,y) 
		 --for i, obj in ipairs(Objects) do

for i = 1, #Objects do 
		     local obj = Objects[i] 
		  if obj:contains(x, y) then

if TrackedObject ~= nil then 
		          TrackedObject.selected = false 
		          end

TrackedObject = obj 
		   obj.selected = true 
		   if obj.colour == Colour.green then 
		   table.insert(Objects, Square(x, y, w/10, w/10)) 
		   else 
		   table.insert(Objects, Circle(x, y, w/20, w/20)) 
		   end 
		   TrackOffsetx = TrackedObject.x - x 
		   TrackOffsety = TrackedObject.y - y 
		   table.remove(Objects, i) 
		   table.insert(Objects, obj) 
		   platform.window:invalidate() 
		   break 
		  end 
		 end 
		end

function on.mouseUp(x,y) 
		      if TrackedObject ~= nil then 
		          TrackedObject.selected = false 
		         end    
		     TrackedObject = nil 
		end

function on.mouseMove(x,y) 
		 if TrackedObject ~= nil then 
		  TrackedObject.x = x + TrackOffsetx 
		  TrackedObject.y = y + TrackOffsety 
		  platform.window:invalidate() 
		 end 
		end

function on.paint(gc) 
		 for _, obj in ipairs(Objects) do 
		  obj:paint(gc) 
		 end 
		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 the transfer of the TrackedObject is achieved.

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