Balls Example

Simple lua code showing event handling, class creation, grabbing objects across the screen, cursor setting...

(Code by Adrien "Adriweb" Bertrand)

Ball = class()

function Ball:init(x,y,r,color)
 self.x = x 
 self.y = y 
 self.r = r 
 self.color = color 
 self.isActive = false 
 self.id = #ballsTable+1
end

function Ball:paint(gc) 
 gc:setColorRGB(unpack(self.color)) 
 gc:fillArc(self.x,self.y,self.r,self.r,0,360)
 if self.isActive then
    gc:setColorRGB(0) 
    gc:drawArc(self.x,self.y,self.r,self.r,0,360)
 end
end

function Ball:move(x,y)
 self.x = x 
 self.y = y 
 platform.window:invalidate()
end

function on.grabDown(x,y) 
 isGrabbing = not isGrabbing
 platform.window:invalidate()
end

function on.mouseUp(x,y)
 cursor.set("default") 
 isGrabbing = false 
 platform.window:invalidate()
end

function on.mouseDown(x,y) 
 isGrabbing = true 
 platform.window:invalidate()
end

function on.mouseMove(x,y)
 if isGrabbing and (trackedBall and trackedBall.isActive) then
    cursor.set("drag grab") 
    txt2 = "moving ball #"..trackedBall.id
    trackedBall:move(x-trackedBall.r/2,y-trackedBall.r/2)
 else
    txt2 = "not moving anything"
    for i,ball in ipairs(ballsTable) do
       if math.abs(ball.x+ball.r/2-x) <= ball.r/1.8 and math.abs(ball.y+ball.r/2-y) <= ball.r/1.8 then
          ball.isActive = true
          trackedBall = ball
       else
           ball.isActive = false
       end
    end 
 end
end

function on.paint(gc)
 for _,ball in ipairs(ballsTable) do
    ball:paint(gc)
 end
 gc:setColorRGB(0,0,0)
 gc:drawString("grabbing : " .. tostring(isGrabbing),2,0,"top")
 gc:drawString(tostring(txt2),2,20,"top")
 gc:drawString("Press Enter to create a Ball object", 2, 190, "top")
end

ballsTable = {}
grabFlag = false
isGrabbing = false
txt2 = "not moving anything"

function on.enterKey()
 ballsTable[#ballsTable+1] = Ball(math.random(10,250), math.random(10,180), 15, {math.random(0,255),math.random(0,255),math.random(0,255)})
end