UIElement:compute_desired_size

Advanced

Computes and returns the size requested by this element for layout purposes. This is called within update_tree.

For leaf elements like Image or Text, this returns how much space they require to draw.

Wrapper and Container elements usually call this method recursively on their children, and combine results with joint data to derive the total desired size.

Usage

ui_element:compute_desired_size()

Returns

Name	Type	Description
width	number	Desired width.
height	number	Desired height.

Examples

This example is the implementation of compute_desired_size for Overlay containers:

Overlay.compute_desired_size = function(self)
  local width, height = 0, 0;
  for child, joint in pairs(self.child_joints) do
    local child_width, child_height = child:desired_size();
    local padding_left, padding_right, padding_top, padding_bottom = joint:padding();
    local h_align, v_align = joint:alignment();
    if h_align ~= "stretch" then
      width = math.max(width, child_width + padding_left + padding_right);
    end
    if v_align ~= "stretch" then
      height = math.max(height, child_height + padding_top + padding_bottom);
    end
  end
  return math.max(width, 0), math.max(height, 0);
end