Click and Drag with Z-order

[herrinbleu]

At the moment, I have several objects overlapping each other and when I click and drag, overlapping objects are all moved.

Code: Select all

function dragging_detect(x, y, button)
  for i,v in ipairs(objects) do
    if x > v.x and x < v.x + v.width
    and y > v.y and y < v.y + v.height then
          v.dragging.active = true
          v.dragging.diffX = x - v.x
          v.dragging.diffY = y - v.y
    end
  end
end

How should I make it such that only the top object is moved?
And also, how can I allow objects clicked to be moved to the top of the z order?

[zorg]

At the moment, I have several objects overlapping each other and when I click and drag, overlapping objects are all moved.

-- Code was here...

How should I make it such that only the top object is moved?
And also, how can I allow objects clicked to be moved to the top of the z order?

Hi and welcome to the forums!

First, let's assume that your objects table is already z-sorted (1==top, #objects==bottom), in which case you only need to do the following small edit:

Code: Select all

function dragging_detect(x, y, button)
  for i,v in ipairs(objects) do
    if x > v.x and x < v.x + v.width
    and y > v.y and y < v.y + v.height then
          v.dragging.active = true
          v.dragging.diffX = x - v.x
          v.dragging.diffY = y - v.y
          -- In lua, the below code works, you don't need any temporary variable to store one of them.
          objects[1], objects[i] = objects[i], objects[1]
          -- And we break so we don't process any other object.
          break
    end
  end
end

This is the simplest solution, although it reorders the objects a bit (swaps the top object with the one the click was registered with, regardless of its x and y position), a bit better solution would be to move the selected to the top, and slide all the objects that were above it by 1.

[herrinbleu]

Thanks for the quick reply!! I managed to figure out how to work around it with another method..

Code: Select all

function dragging_detect(x, y, button)
  for i,v in ipairs(objects) do
    if x > v.x and x < v.x + v.width
    and y > v.y and y < v.y + v.height then
          v.dragging.active = true
          v.dragging.diffX = x - v.x
          v.dragging.diffY = y - v.y
   	  -- Instead of break, I used return. I'm not sure if there's a difference.
          return
          -- This allows the objects to slide by 1.
          top = objects[i]
      	  table.remove(objects, i)
     	  table.insert(objects, top)
    end
  end

[zorg]

Yep, that looks workable too!
The difference between break and return is that break would only break out of the for loop, and the code would continue below that block; return exits the whole function.