crystal.input.add_mouse_target

Advanced

Registers a recipient for mouse interactions and its bounding box. After the next frame update, the recipient passed in to this function may become the current_mouse_target. The list of available mouse targets is cleared each frame, which means this function should be called every frame as long as the interactive object is on screen. When multiple bounding boxes are overlapping, mouse targets added last take precedence.

Coordinates passed into this function should be positions in the game window, comparable with the output of love.mouse.getPosition.

This function should rarely be needed, as Crystal UI elements offer a higher level API to implement mouse interactions.

Usage

crystal.input.add_mouse_target(recipient, left, right, top, bottom)

Arguments

Name	Type	Description
recipient	table	Any table representing the object at this location which can interact with the mouse.
left	number	Left edge of the interactive object bounding box.
right	number	Right edge of the interactive object bounding box.
top	number	Top edge of the interactive object bounding box.
bottom	number	Bottom edge of the interactive object bounding box.

For recipients that need finer hit detection than a bounding box or conditional activation, the recipient table may implement an overlaps_mouse method. If this method exists and the mouse is within the bounding box, overlaps_mouse will be called with the following arguments after self:

• A player_index number identifying the player operating the mouse
• Mouse x position from love.mouse.getPosition
• Mouse y position from love.mouse.getPosition

If overlaps_mouse returns true, the recipient will become the current mouse target. If it returns false, other mouse targets at this location will be considered.

Examples

This example defines a scene with an interactive mouse object in the top left of the game window.

local Scene = Class("MyScene", crystal.Scene);

Scene.init = function(self)
  self.clickable_box = { name = "Cardboard box" };
end

Scene.update = function(self)
  local under_mouse = crystal.input.current_mouse_target();
  if under_mouse then
    print(under_mouse.name); -- Prints "Cardboard box" while the mouse is within the top left of the game window
  end
end

Scene.draw = function(self)
  crystal.input.add_mouse_target(self.clickable_box, 0, 100, 0, 100);
end

This example registers an interactive mouse object with a circular hitbox.

local circle = {
  x = 50,
  y = 50,
  radius = 20,
  overlaps_mouse = function(self, player_index, mouse_x, mouse_y)
    return math.distance(self.x, self.y, mouse_x, mouse_y) < self.radius;
  end
};

crystal.input.add_mouse_target(circle, 30, 70, 30, 70);