Tutorial:Callback Functions (Français)

Les fonctions callback dans LÖVE sont utilisées par le moteur pour effectuer des tâches diverses et sont toutes facultatives. Toutefois, une jeu complet les utilisera probablement quasiment toutes, il est donc interessant de les connaitre.

love.load

function love.load()
   image = love.graphics.newImage("cake.jpg")
   local f = love.graphics.newFont(12)
   love.graphics.setFont(f)
   love.graphics.setColor(0,0,0,255)
   love.graphics.setBackgroundColor(255,255,255)
end

Cette fonction est appelée une seule fois, lorsque le jeu est lancé, et est généralement celle où vous chargez des ressources, initialisez des variables et des paramètres spécifiques. Toutes ces choses peuvent aussi être faites n'importe où ailleurs, mais de les faire ici signifie qu'ils sont fait une seule fois, de gagner beaucoup de ressources système.

love.update

function love.update(dt)
   if love.keyboard.isDown("up") then
      num = num + 100 * dt -- this would increment num by 100 per second
   end
end

This function is called continuously and will probably be where most of your math is done. 'dt' stands for "delta time" and is the amount of seconds since the last time this function was called (which is usually a small value like 0.025714).

love.draw

function love.draw()
   love.graphics.draw(image, imgx, imgy)
   love.graphics.print("Click and drag the cake around or use the arrow keys", 10, 10)
end

love.draw is where all the drawing happens (if that wasn't obvious enough already) and if you call any of the love.graphics.draw outside of this function then it's not going to have any effect. This function is also called continuously so keep in mind that if you change the font/color/mode/etc at the end of the function then it will have a effect on things at the beginning of the function. For example:

function love.load()
   love.graphics.setColor(0,0,0)
end

function love.draw()
   love.graphics.print("This text is not black because of the line below", 100, 100)
   love.graphics.setColor(255,0,0)
   love.graphics.print("This text is red", 100, 200)
end

love.mousepressed

function love.mousepressed(x, y, button)
   if button == 'l' then
      imgx = x -- move image to where mouse clicked
      imgy = y
   end
end

This function is called whenever a mouse button is pressed and it receives the button and the coordinates of where it was pressed. The button can be any of the constants. This function goes very well along with love.mousereleased.

love.mousereleased

function love.mousereleased(x, y, button)
   if button == 'l' then
      fireSlingshot(x,y) -- this totally awesome custom function is defined elsewhere
   end
end

This function is called whenever a mouse button is released and it receives the button and the coordinates of where it was released. You can have this function together with love.mousepressed or separate, they aren't connected in any way.

love.keypressed

function love.keypressed(key, unicode)
   if key == 'b' then
      text = "The B key was pressed."
   elseif key == 'a' then
      a_down = true
   end
end

This function is called whenever a keyboard key is pressed and receives the key that was pressed. The key can be any of the constants. This functions goes very well along with love.keyreleased.

love.keyreleased

function love.keyreleased(key, unicode)
   if key == 'b' then
      text = "The B key was released."
   elseif key == 'a' then
      a_down = false
   end
end

This function is called whenever a keyboard key is released and receives the key that was released. You can have this function together with love.keypressed or separate, they aren't connected in any way.

Those are the callback functions and their basic usage.

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